Publications
| Title | Abstract | Year(sorted ascending) Filter | PMID Filter |
|---|
| zymomonas mobilis--science and industrial application. | zymomonas mobilis is undoubtedly one of the most unique bacterium within the microbial world. known since 1912 under the names termobacterium mobilis, pseudomonas linderi, and zymomonas mobilis, reviews on its uniqueness have been published in 1977 and 1988. the bacterium zymomonas mobilis not only exhibits an extraordinarily uniqueness in its biochemistry, but also in its growth behavior, energy production, and response to culture conditions, as well as cultivation techniques used. this uniquen ... | 1993 | 8477453 |
| electroporation and dna-dependent cell death in murine macrophages. | the difficulty of transfecting primary macrophages and macrophage cell lines has meant that relatively few studies on regulation of gene expression have been performed in these cells. this study has optimized an electroporation procedure for the macrophage cell line raw 264, but shows that introduction of dna into the cytoplasm of primary macrophages by electroporation is toxic to the cells. it is proposed that this cell death may have a physiological role in defence against certain viral infect ... | 1993 | 8486399 |
| use of in vivo 13c nuclear magnetic resonance spectroscopy to follow sugar uptake in zymomonas mobilis. | a noninvasive, in situ, in vivo, and anomer-specific method for studying membrane transport of sugars in bacteria is presented. high-resolution 13c nmr was used to measure the distribution of alpha- and beta-xylose, maltose, mes buffer, and ethanol in the extracellular and the cytoplasmic compartments in dense cell suspensions of zymomonas mobilis, an aerotolerant bacterium that transports xylose but does not further metabolize it. the method relied on a difference in the magnetic susceptibility ... | 1993 | 8489007 |
| purification and characterization of an oxygen-labile, nad-dependent alcohol dehydrogenase from desulfovibrio gigas. | a nad-dependent, oxygen-labile alcohol dehydrogenase was purified from desulfovibrio gigas. it was decameric, with subunits of m(r) 43,000. the best substrates were ethanol (km, 0.15 mm) and 1-propanol (km, 0.28 mm). n-terminal amino acid sequence analysis showed that the enzyme belongs to the same family of alcohol dehydrogenases as zymomonas mobilis adh2 and bacillus methanolicus mdh. | 1993 | 8491707 |
| cloning and expression in escherichia coli of the dnak gene of zymomonas mobilis. | the dnak protein of zymomonas mobilis (dnakz) was identified and found to be 80% identical to the dnak protein of escherichia coli on the basis of the sequence of the n-terminal 21 amino acids. the dnakz gene was cloned and found to be expressed in a thermosensitive dnak mutant of escherichia coli. expression of the foreign gene restored a thermoresistant phenotype but failed to modulate the heat shock response in e. coli. | 1993 | 8491740 |
| nucleotide and derived amino acid sequences of an extracellular sucrase gene (invb) of zymomonas mobilis zm1 (atcc10988). | dna sequence analysis of a previously cloned 4.5 kb dna fragment showed that the extracellular sucrase gene (invb) of zymomonas mobilis was located in the 155 bp downstream of levansucrase gene (levu). the invb gene had an open reading frame of 1242 bp and the deduced amino acid sequence was 413 residues with a molecular weight of 46,107. the translated sequence of z. mobilis invb was in good agreement with the 10 n-terminal amino acid residues determined by amino acid sequencing. the amino acid ... | 1994 | 8086457 |
| metal-catalyzed oxidation of fe2+ dehydrogenases. consensus target sequence between propanediol oxidoreductase of escherichia coli and alcohol dehydrogenase ii of zymomonas mobilis. | we have studied two enzymes of a newly described family of dehydrogenases with high sequence homology, 1,2-propanediol oxidoreductase of escherichia coli and alcohol dehydrogenase ii of zymomonas mobilis. these enzymes perform their metabolic role under anaerobic conditions; in the presence of oxygen, they show a very similar inactivation pattern by a metal-catalyzed oxidation system. titration of histidine residues with diethyl pyrocarbonate showed one histidine residue less in the oxidized enz ... | 1994 | 8120011 |
| reconstruction of glucose uptake and phosphorylation in a glucose-negative mutant of escherichia coli by using zymomonas mobilis genes encoding the glucose facilitator protein and glucokinase. | expression of the zymomonas mobilis glf (glucose facilitator protein) and glk (glucokinase) genes in escherichia coli zsc113 (glucose negative) provided a new functional pathway for glucose uptake and phosphorylation. both genes were essential for the restoration of growth in glucose minimal medium and for acid production on glucose-macconkey agar plates. | 1994 | 8144485 |
| [design of recombinant plasmids for effective zymomonas mobilis pyruvate decarboxylase (pdk) gene expression in bacillus subtilis cells]. | the pdk gene from z. mobilis localized on the 4.7-kb sphi dna fragment in plasmid pb201 was subcloned using drai restriction endonuclease into the smai site of the phage cloning vector m13mp19. the derivatives of m13mp19 obtained, containing 1.8-kb inserts of the pdk gene in two opposite orientations, were used for dna sequencing and site-directed mutagenesis. the latter was performed using polymerase chain reaction (pcr) and synthetic deoxyribonucleotides of appropriate structure as primers. in ... | 1994 | 8145744 |
| molecular characterization of microbial alcohol dehydrogenases. | there is an astonishing array of microbial alcohol oxidoreductases. they display a wide variety of substrate specificities and they fulfill several vital but quite different physiological functions. some of these enzymes are involved in the production of alcoholic beverages and of industrial solvents, others are important in the production of vinegar, and still others participate in the degradation of naturally occurring and xenobiotic aromatic compounds as well as in the growth of bacteria and ... | 1994 | 8185833 |
| investigation of the cofactor-binding site of zymomonas mobilis pyruvate decarboxylase by site-directed mutagenesis. | several enzymes require thiamin diphosphate (thdp) as an essential cofactor, and we have used one of these, pyruvate decarboxylase (pdc; ec 4.1.1.1) from zymomonas mobilis, as a model for this group of enzymes. it is well suited for this purpose because of its stability, ease of purification and its simple kinetic properties. a sequence motif of approx. 30 residues, beginning with a glycine-aspartate-glycine (-gdg-) triplet and ending with a double asparagine (-nn-) sequence, has been identified ... | 1994 | 8198554 |
| molecular cloning and sequence analysis of an azospirillum brasilense indole-3-pyruvate decarboxylase gene. | azospirillum brasilense isolated from the rhizosphere of different plants has the ability to excrete indole-3-acetic acid (iaa) into the culture media. cosmid p0.2, isolated from an a. brasilense sp245 genome library in plafr1, complements the tn5-induced mutant spm7918 of a. brasilense sp6 which excretes reduced amounts of iaa. restriction mapping and gene expression studies identified a bglii-ecori 4.3 kb fragment of p0.2 sufficient for the restoration of high levels of iaa production in mutan ... | 1994 | 8202090 |
| molecular analysis of the erwinia chrysanthemi region containing the kdga and zwf genes. | the pathways of pectin and galacturonate catabolism in erwinia chrysanthemi converge to form a common intermediate, 2-keto-3-deoxygluconate, which is phosphorylated to form 2-keto-3-deoxy-6-phosphogluconate (kdgp) and then cleaved by the aldolase encoded by the kdga gene. we cloned the kdga gene of the e. chrysanthemi strain 3937 by complementing an escherichia coli kdga mutation, using an rp4-derivative plasmid. restriction mapping of the kdga region and isolation of kdga-lac fusions allowed th ... | 1994 | 8145647 |
| crystallization and preliminary x-ray analysis of glucose-fructose oxidoreductase from zymomonas mobilis. | glucose-fructose oxidoreductase (e.c. 1.1.99.-) from the ethanol-producing gram-negative bacterium zymomonas mobilis is a periplasmic, soluble enzyme that forms a homotetramer of 160 kda with one nadp(h) cofactor per subunit that is tightly, but noncovalently, bound. the enzyme was crystallized by the hanging drop vapor diffusion method using sodium citrate as precipitant. the obtained crystals belong to the space group p2(1)2(1)2, with unit cell constants of 84.6 a, 94.1 a, and 117.0 a, consist ... | 1994 | 7756998 |
| cloning and characterization of a pair of genes that stimulate the production and secretion of zymomonas mobilis extracellular levansucrase and invertase. | a 1.7-kb dna fragment cloned from zymomonas mobilis genomic dna complemented the inability to grow on sucrose of a suc- mutant of z. mobilis that was deficient in the production of both extracellular levansucrase and invertase. analysis of the nucleotide sequence of the fragment found two open reading frames (orfs), both of which did not correspond to the structural gene for the levansucrase or the invertase. by subcloning each orf into two different suc- mutants of z. mobilis, it has been found ... | 1994 | 7764692 |
| strain improvement of zymomonas mobilis for ethanol production. | 1994 | 7764783 | |
| cloning of the acetobacter xylinum cellulase gene and its expression in escherichia coli and zymomonas mobilis. | a dna fragment corresponding to carboxymethylcellulase activity of acetobacter xylinum ifo 3288 was isolated and cloned in escherichia coli, and the dna sequence was determined. the dna fragment sequenced had an open-reading frame of 654 base pairs that encoded a protein of 218 amino acid residues with a deduced molecular mass of 23,996 da. the protein encoded in the dna fragment expressed in e. coli hydrolyzed a carboxymethylcellulose. this gene was subcloned into the shuttle vector [pza22; mis ... | 1994 | 7765731 |
| cloning, sequencing and expression of stress genes from the ethanol-producing bacterium zymomonas mobilis: the groesl operon. | zymomonas mobilis is unique among bacteria in its ability to produce high levels of ethanol (etoh) during fermentation. elevated etoh concentration, like elevated temperature, is a microbial stress and a universal inducer of stress proteins. for z. mobilis, exposure to high levels of etoh represents a natural stress. by using a simple strategy which combines the genetic tools of escherichia coli and bacillus subtilis, we have cloned genes encoding two of the most abundant stress proteins in z. m ... | 1994 | 7926837 |
| polymerase chain reaction-based random mutagenesis: production and characterization of thermostable mutants of zymomonas mobilis alcohol dehydrogenase-2. | the adhb gene encoding alcohol dehydrogenase-2 from zymomonas mobilis has been subjected to random mutagenesis to obtain more thermostable variants of the enzyme. random mutagenesis was accomplished using the polymerase chain reaction in mutagenic conditions. the optimum conditions involved restricting the concentration of one nucleotide to approximately one-tenth the normal amount. this introduced mutations at an average rate of 1 base in 600 in a 30-cycle pcr, sufficient to ensure that the maj ... | 1994 | 7950371 |
| isolation of intergeneric hybrids between bacillus subtilis and zymomonas mobilis and the production of thermostable amylase by hybrids. | stable hybrids were obtained by protoplast fusion between bacillus subtilis and zymomonas mobilis. all the hybrids were able to hydrolyse starch and possessed ampicillin- and tetracycline-resistant phenotypes. two of the hybrids, bz-1 and bz-2, were hyperproducers of alpha-amylase. the enzyme produced by these hybrids exhibited increased thermostability. the results show that stable intergeneric gene transfer can be achieved through poly(ethylene glycol)-mediated protoplast fusion between two in ... | 1994 | 7917061 |
| mechanism of alanine excretion in recombinant strains of zymomonas mobilis. | a thiamine-auxotrophic strain of zymomonas mobilis (cp4thi/pzy73), in which the alad gene of bacillus sphaericus coding for the alanine dehydrogenase was expressed, synthesizes and excretes alanine at high rates after thiamine starvation and in the presence of high external ammonium concentrations. the mechanism of alanine excretion was studied in this recombinant zymomonas mobilis strain. under production conditions the internal alanine concentration reached values of up to 280 mm and excretion ... | 1994 | 7986805 |
| reversible dissociation and unfolding of pyruvate decarboxylase from zymomonas mobilis. | the denaturation and renaturation process of pyruvate decarboxylase (pdc) from zymomonas mobilis (atcc 29191) has been investigated using guanidine hydrochloride and urea as denaturing agents. the quarternary structure of the homotetramer is strongly stabilized by the cofactors mg2+ and thiamine diphosphate (tdp). the structural transitions were monitored by activity measurements, fluorescence spectroscopy, circular dichroism and gel-filtration chromatography. a three-step denaturation process, ... | 1994 | 7925382 |
| sorbitol promotes growth of zymomonas mobilis in environments with high concentrations of sugar: evidence for a physiological function of glucose-fructose oxidoreductase in osmoprotection. | the gram-negative ethanologenic bacterium zymomonas mobilis is able to grow in media containing high concentrations of glucose or other sugars. a novel compatible solute for bacteria, sorbitol, which enhances growth of z. mobilis at glucose concentrations exceeding 0.83 m (15%), is described. added sorbitol was accumulated intracellularly up to 1 m to counteract high external glucose concentrations (up to 1.66 m or 30%). accumulation of sorbitol was triggered by a glucose upshift (e.g., from 0.3 ... | 1994 | 8002594 |
| ethanolic fermentation in transgenic tobacco expressing zymomonas mobilis pyruvate decarboxylase. | during oxygen limitation in higher plants, energy metabolism switches from respiration to fermentation. as part of this anaerobic response the expression of genes encoding pyruvate decarboxylase (pdc) and alcohol dehydrogenase (adh) is strongly induced. in addition there is ample evidence for post-translational regulation. in order to understand this multi-level regulation of the anaerobic response, we provided tobacco with the constitutive capacity of ethanolic fermentation by expressing a pdc ... | 1994 | 8026460 |
| analysis of the escherichia coli genome. v. dna sequence of the region from 76.0 to 81.5 minutes. | the dna sequence of a 225.4 kilobase segment of the escherichia coli k-12 genome is described here, from 76.0 to 81.5 minutes on the genetic map. this brings the total of contiguous sequence from the e.coli genome project to 725.1 kb (76.0 to 92.8 minutes). we found 191 putative coding genes (orfs) of which 72 genes were previously known, and 110 of which remain unidentified despite literature and similarity searches. seven new genes--arse, arsf, arsg, tref, xylr, xylg, and xylh--were identified ... | 1994 | 8041620 |
| two genes for carbohydrate catabolism are divergently transcribed from a region of dna containing the hexc locus in pseudomonas aeruginosa pao1. | the hexc locus of pseudomonas aeruginosa pao1 was localized to a 247-bp segment of chromosomal dna on the multicopy broad-host-range vector pro1614. the presence of this plasmid (ppz196) in strain pao1 produced the so-called "hexc effect," a two- to ninefold increase in the activities of four carbohydrate catabolism enzymes, glucokinase, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydratase, and 2-keto-3-deoxy-6-phosphogluconate aldolase. the extent of the hexc effect was restricted, ... | 1994 | 8045900 |
| glucose repression in streptomyces coelicolor a3(2): a likely regulatory role for glucose kinase. | the glucose kinase gene (glka-orf3) of streptomyces coelicolor a3(2) plays an essential role in glucose utilisation and in glucose repression of a variety of genes involved in the utilisation of alternative carbon sources. these genes include daga, which encodes an extracellular agarase that permits agar utilisation. suppressor mutants of glka-orf3 deletion strains capable of utilising glucose (glc+) arise at a frequency of about 10(-5) on prolonged incubation. the glc+ phenotype of the mutants ... | 1994 | 8052232 |
| characterization and sequence of phoc, the principal phosphate-irrepressible acid phosphatase of morganella morganii. | phosphatase activities were investigated in morganella morganii, which is one of the few enterobacterial species producing high-level phosphate-irrepressible acid phosphatase activity (hpap phenotype), and the gene encoding the major phosphate-irrepressible acid phosphatase was cloned, sequenced, and its product characterized. using p-nitrophenyl phosphate as substrate, morganella produced a major phosphate-irrepressible acid phosphatase (named phoc) which is associated with the hpap phenotype, ... | 1994 | 8081499 |
| comparative fermentation behaviour and chemical characteristics of saccharomyces and zymomonas fermented culled apple juice. | ethanol production from culled apple juice showed that fermentability of the juice could be enhanced by addition of dahp or ammonium sulphate in saccharomyces and dahp in zymomonas fermentation. addition of trace elements inhibited both the fermentations and ethanol, consequently. with respect to by-products of fermentation, no clear advantage of zymomnas fermentation of culled apple juice could be observed. differences in physico-chemical characteristics of the fermented apple juice were also n ... | 1994 | 7896319 |
| differences in response of zymomonas mobilis and saccharomyces cerevisiae to change in extracellular ethanol concentration. | in high cell density batch fermentations, zymomonas mobilis produced 91 g l(-1) ethanol in 90 min but culture viability fell significantly. similar viability losses in rapid fermentations by yeast have recently been shown to be attributable in part to the high rate of change of the extracellular ethanol concentration. however, in simulated rapid fermentations in which ethanol was pumped continuously to low cell density z. mobilis suspensions, increases in the rate of change of ethanol concentrat ... | 1994 | 18615609 |
| saccharification and fermentation of sugar cane bagasse by klebsiella oxytoca p2 containing chromosomally integrated genes encoding the zymomonas mobilis ethanol pathway. | pretreatment of sugar cane bagasse is essential for a simultaneous saccharification and fermentation (ssf) process which uses recombinant klebsiella oxytoca strain p2 and genencor spezyme ce. strain p2 has been genetically engineered to express zymomonas mobilis genes encoding the ethanol pathway and retains the native ability to transport and metabolize cellobiose (minimizing the need for extracellular cellobiase). in ssf studies with this organism, both the rate of ethanol production and ethan ... | 1994 | 18618690 |
| the ice nucleation gene from pseudomonas syringae as a sensitive gene reporter for promoter analysis in zymomonas mobilis. | the expression of the ice nucleation gene inaz from pseudomonas syringae in zymomonas mobilis strains under the control of three different promoters was investigated to establish the utility of the gene as a reporter and examine the possible use of the organism as a source of ice nuclei for biotechnological applications. a promoterless version of the inaz gene was placed under the control of three different promoters: p(infpdc) (pyruvate decarboxylase), a homologous strong promoter from z. mobil ... | 1995 | 16534909 |
| metabolic engineering of a pentose metabolism pathway in ethanologenic zymomonas mobilis. | the ethanol-producing bacterium zymomonas mobilis was metabolically engineered to broaden its range of fermentable substrates to include the pentose sugar xylose. two operons encoding xylose assimilation and pentose phosphate pathway enzymes were constructed and transformed into z. mobilis in order to generate a strain that grew on xylose and efficiently fermented it to ethanol. thus, anaerobic fermentation of a pentose sugar to ethanol was achieved through a combination of the pentose phosphate ... | 1995 | 17791346 |
| useful mutants of zymomonas mobilis alcohol dehydrogenase-2 obtained by the use of polymerase chain reaction random mutagenesis. | 1995 | 7484407 | |
| isolation and sequence analysis of rpoh genes encoding sigma 32 homologs from gram negative bacteria: conserved mrna and protein segments for heat shock regulation. | the rpoh genes encoding homologs of escherichia coli sigma 32 (heat shock sigma factor) were isolated and sequenced from five gram negative proteobacteria (gamma or alpha subgroup): enterobacter cloacae (gamma), serratia marcescens (gamma), proteus mirabilis (gamma), agrobacterium tumefaciens (alpha) and zymomonas mobilis (alpha). comparison of these and three known genes from e.coli (gamma), citrobacter freundii (gamma) and pseudomonas aeruginosa (gamma) revealed marked similarities that should ... | 1995 | 7501460 |
| purification and characterization of cycloinulooligosaccharide fructanotransferase (cftase) from bacillus circulans mci-2554. | cycloinulooligosaccharide fructanotransferase (cftase) that produces cyclofructan from inulin was purified about 69-fold from a culture broth of bacillus circulans mci-2554 by column chromatographies on deae-toyopearl, qae-toyopearl, hydroxyapatite, and phenyl-sepharose. the molecular mass of the enzyme was estimated to be 115 kda by sds-polyacrylamide gel electrophoresis and gel filtration, indicating a monomer structure. maximal activity was observed at ph 7.5 and 45 degrees c. the enzyme was ... | 1995 | 7765973 |
| cloning and characterization of zymomonas mobilis genes encoding extracellular levansucrase and invertase. | the genes encoding the extracellular levansucrase and invertase of zymomonas mobilis have been cloned and sequenced. the levansucrase gene, sucze2, spans 1269 bp and encodes an m(r) 46,790 polypeptide, and the invertase gene, sucze3, is of 1239 bp and encodes an m(r) 46,110 polypeptide. the 5'-terminal sequences of both genes corresponded to the n-terminal amino acid sequences of the secreted levansucrase and invertase, implying that the secretion of both enzymes does not involve proteolytic pro ... | 1995 | 7766026 |
| functional expression of the glucose transporter of zymomonas mobilis leads to restoration of glucose and fructose uptake in escherichia coli mutants and provides evidence for its facilitator action. | the zymomonas mobilis genes encoding the glucose facilitator (glf), glucokinase (glk), or fructokinase (frk) were cloned and expressed in a laciq-ptac system using escherichia coli k-12 mutants deficient in uptake and phosphorylation of glucose and fructose. growth on glucose or fructose was restored when the respective genes (glf-glk or glf-frk) were expressed. in e. coli glf+ strains, both glucose and fructose were taken up via facilitated diffusion (km, 4.1 mm for glucose and 39 mm for fructo ... | 1995 | 7768841 |
| evaluation of image analysis and laser granulometry for microbial cell sizing. | a direct cell size measurement technique and an image analysis based sizing method were developed. the former consisted of a manual size measurement of the two-dimensional cell images on a video screen, with automatic data recording. this method was chosen as the reference. the latter, a semiautomatic method took advantage of a commercial computer program designed for image processing and particle morphology analysis. it gave average and median size values which were compatible with the manual m ... | 1995 | 7771762 |
| molecular cloning and characterization of the extracellular sucrase gene (sacc) of zymomonas mobilis. | the zymomonas mobilis gene sacc that encodes the extracellular sucrase (protein b46) was cloned and expressed in escherichia coli. the gene was found to be present downstream to the already described levansucrase gene sacb in the cloned chromosomal fragment of z. mobilis. the expression product was different from sacb and exhibited sucrase but not levansucrase activity; therefore, sacc behaves like a true sucrase. expression of sacc in e. coli jm109 and xl1 was very low; overexpression was obser ... | 1995 | 7778976 |
| enzymes from zymomonas mobilis and their application to glucose determination. | 1995 | 7785863 | |
| cloning, sequencing and characterization of the alkaline phosphatase gene (phod) from zymomonas mobilis. | the phod gene encoding the membrane-bound alkaline phosphatase (alpi) from zymomonas mobilis cp4 was cloned and sequenced. both the translated sequence and the properties of the recombinant enzyme were unusual. z. mobilis alpi was monomeric (m(r) 62,926) and hydrolysed nucleotides more effectively than sugar phosphates. the translated sequence contained a single hydrophobic segment near the n-terminus which may serve as a membrane-anchor in z. mobilis, although the recombinant enzyme was recover ... | 1995 | 7875572 |
| imidazole acetol phosphate aminotransferase in zymomonas mobilis: molecular genetic, biochemical, and evolutionary analyses. | hish encodes imidazole acetol phosphate (iap) aminotransferase in zymomonas mobilis and is located immediately upstream of tyrc, a gene which codes for cyclohexadienyl dehydrogenase. a plasmid containing hish was able to complement an escherichia coli histidine auxotroph which lacked the homologous aminotransferase. dna sequencing of hish revealed an open reading frame of 1,110 bp, encoding a protein of 40,631 da. the cloned hish product was purified from e. coli and estimated by sodium dodecyl ... | 1995 | 7883715 |
| zymomonas mobilis squalene-hopene cyclase gene (shc): cloning, dna sequence analysis, and expression in escherichia coli. | using a dna probe from the gene encoding squalene-hopene cyclase (shc, ec 5.4.99.-) from the gram-positive bacterium alicyclobacillus acidocaldarius, we have cloned a 4.3 kb hindiii fragment of chromosomal dna from zymomonas mobilis. an open reading frame of 1977 bp was detected that could encode a protein of 658 amino acids with a calculated molecular mass of 74077 da. under the control of lac or tac promoters, this gene, shc, was expressed in escherichia coli k12 strains and its product had sq ... | 1995 | 7894707 |
| construction of an integrative shuttle vector for zymomonas mobilis. | an integrative shuttle vector, pzmocp1, was constructed by ligating ecorv digests of the plasmid cloning vector pbluescript and pzmp1, a cryptic plasmid of zymomonas mobilis proimi a1. the 7.2-kb plasmid pzmocp1 replicated in escherichia coli and could also be transferred from this host by electroporation to z. mobilis atcc 29191. the transformants were selected by ampicillin resistance. the integrative characteristic was detected by hybridization in situ. the vector was stably maintained in z. ... | 1995 | 7590162 |
| characterization of the zymomonas mobilis glucose facilitator gene product (glf) in recombinant escherichia coli: examination of transport mechanism, kinetics and the role of glucokinase in glucose transport. | zymomonas mobilis is known to transport glucose by a facilitated diffusion process. a putative glucose facilitator gene (glf), closely related to a large family of glucose transporters, is located in a cluster of genes that code for enzymes of glucose metabolism. the z. mobilis glf gene is able to complement glucose transport in an escherichia coli strain that is defective in native glucose transport and glucokinase. in this study, the recombinant e. coli was shown to be capable of influx counte ... | 1995 | 7596282 |
| the glutamate uptake regulatory protein (grp) of zymomonas mobilis and its relation to the global regulator lrp of escherichia coli. | after being expressed in escherichia coli jc5412, which is defective in glutamate transport, a zymomonas mobilis gene which enabled this strain to grow on glutamate was cloned. this gene encodes a protein with 33% amino acid identity to the leucine-responsive regulatory protein (lrp) of e. coli. although overall glutamate uptake in e. coli was increased, the protein encoded by the cloned fragment repressed the secondary h+/glutamate transport system gltp by interaction with the promoter region o ... | 1995 | 7665494 |
| sequence analysis and overexpression of the zymomonas mobilis tgt gene encoding trna-guanine transglycosylase: purification and biochemical characterization of the enzyme. | trna-guanine transglycosylase (tgt) is involved in the biosynthesis of the hypermodified trna nucleoside queuosine (q). it catalyzes the posttranscriptional base exchange of the q precursor 7-aminomethyl-7-deazaguanine (preq1) with the genetically encoded guanine in the anticodon of trna(asp), trna(asn), trna(his), and trna(tyr). a partially sequenced gene upstream of the dna ligase (lig) gene of the zymomonas mobilis chromosome shows strong homology to the tgt gene of escherichia coli (k.b. sha ... | 1995 | 7665516 |
| kinetic analysis of the activation of zymomonas mobilis glucokinase by phosphate. | a detailed kinetic analysis of glucokinase ec 2.7.1.2 from zymomonas mobilis has been carried out. this enzyme has an absolute requirement for inorganic phosphate as activator, and the kinetic behaviour can be interpreted as a steady-state ordered mechanism in which glucose is the first substrate. values for each of the kinetic constants have been obtained for the conditions i = 0.12, 30 degrees c, and ph 7.0. direct binding studies have confirmed that atp does not bind to the enzyme without glu ... | 1995 | 7599171 |
| the effect of temperature on enzymes used in diagnostics. | a number of enzymes that are used in clinical analysis have been studied in relation to the effect of temperature on their activity. both vmax and km were determined over a temperature range from 13 to 55 degrees c. whereas vmax values increased steadily until denaturation point with all enzymes, the effect of temperature on km was more variable. with most enzymes there was a gradual increase in km, often with a sharp rise close to the denaturation temperature. in most cases, km did not increase ... | 1995 | 7664474 |
| a novel aerobic respiratory chain-linked nadh oxidase system in zymomonas mobilis. | membrane vesicles prepared from zymomonas mobilis oxidized nadh exclusively, whereas deamino-nadh was little oxidized. in addition, the respiratory chain-linked nadh oxidase system exhibited only a single apparent km value of approximately 66 microm for nadh. the nadh oxidase was highly sensitive to the respiratory chain inhibitor 2-heptyl-4-hydroxyquinoline-n-oxide. however, the nadh:quinone oxidoreductase was not sensitive to 2-heptyl-4-hydroxyquinoline-n-oxide and was highly resistant to anot ... | 1995 | 7665502 |
| comparative energetics of glucose and xylose metabolism in ethanologenic recombinant escherichia coli b. | this study compared the anaerobic catabolism of glucose and xylose by a patented, recombinant ethanologenic escherichia coli b 11303:ploi297 in terms of overall yields of cell mass (growth), energy (atp), and end product (ethanol). batch cultivations were conducted with ph-controlled stirred-tank bioreactors using both a nutritionally rich, complex medium (luria broth) and a defined salts minimal medium and growth-limiting concentrations of glucose or xylose. the value of gamma atp was determine ... | 1995 | 7668846 |
| analysis of intact hopanoids and other lipids from the bacterium zymomonas mobilis by high-performance liquid chromatography. | hopanoids and other lipids were extracted from zymomonas mobilis and quantitatively analyzed by high-performance liquid chromatography. previous methods for hopanoid analysis required derivatization of the hopanoids via periodate oxidation or acetylation. the current method employs a normal-phase silica gel column, a ternary gradient of hexane-isopropanol-water-triethylamine, and detection with a flame ionization detector. three major hopanoid classes were separated and quantified by this new me ... | 1995 | 7710085 |
| semipreparative separation of intact hopanoids from zymomonas mobilis. | hopanoids are an important class of molecules that play a structural and physiological role in the membrane processes of prokaryotic and plant cells. studies on the function of hopanoids require milligram quantities but have been limited by current procedures for isolation and characterization: most separations have isolated only derivatized compounds of hopane in microgram quantities. our method employs aminopropyl bonded-phase solid-phase extraction columns with sequential elution and silica s ... | 1995 | 7710086 |
| purification and characterization of an extracellular levansucrase from pseudomonas syringae pv. phaseolicola. | levansucrase (ec 2.4.1.10), an exoenzyme of pseudomonas syringae pv. phaseolicola, was purified to homogeneity from the cell supernatant by chromatography on tmae-fraktogel and butyl-fraktogel. the enzyme has molecular masses of 45 kda under denaturing conditions and 68 kda during gel filtration of the native form. in isoelectric focusing, active bands appeared at ph 3.55 and 3.6. maximum sucrose cleaving activities were measured at ph 5.8 to 6.6 and 60 degrees c. the enzyme was highly tolerant ... | 1995 | 7751294 |
| improved strains of recombinant escherichia coli for ethanol production from sugar mixtures. | hemicellulose hydrolysates of agricultural residues often contain mixtures of hexose and pentose sugars. ethanologenic escherichia coli that have been previously investigated preferentially ferment hexose sugars. in some cases, xylose fermentation was slow or incomplete. the purpose of this study was to develop improved ethanologenic e. coli strains for the fermentation of pentoses in sugar mixtures. using fosfomycin as a selective agent, glucose-negative mutants of e. coli ko11 (containing chro ... | 1995 | 7766137 |
| the cyanobacterium synechococcus sp. strain pcc 7942 contains a second alkaline phosphatase encoded by phov. | a gene (phov) encoding an alkaline phosphatase from synechococcus sp. strain pcc 7942 was isolated by screening a plasmid gene bank for expression of alkaline phosphatase activity in escherichia coli jm103. two independent clones carrying the same alkaline-phosphatase-encoding gene were isolated. one of these clones (pkw1) was further analysed and the nucleotide sequence of a contiguous 3234 bp dna fragment was determined. two complete open reading frames (orf1 and phov) and an incomplete orf3 w ... | 1995 | 8574398 |
| development of a gene reporter system in moderately halophilic bacteria by employing the ice nucleation gene of pseudomonas syringae. | the expression of the ice nucleation gene inaz of pseudomonas syringae in several moderate halophiles was investigated to establish its utility as a reporter for promoter activity and gene expression studies in these biotechnologically and environmentally important bacteria. a promoterless version of inaz was introduced in two different restriction sites and at both orientations in a recombinant plasmid able to replicate in moderate halophiles and, in particular, within the sequence of its phe1 ... | 1995 | 8526492 |
| the replacement of trp392 by alanine influences the decarboxylase/carboligase activity and stability of pyruvate decarboxylase from zymomonas mobilis. | the bulky tryptophan residue 392 located in the deep cleft leading to the active center of pyruvate decarboxylase (pdc) from zymomonas mobilis was changed to alanine which is found in the equivalent position of pdc from yeast. the mutation reduced the decarboxylase activity towards pyruvate by a factor of two (60-70 u/mg), whereas the km (1.1 mm in mes/koh buffer) remains unchanged compared with the wild-type enzyme. the apparent km for thiamine diphosphate (thiamin-p2) in the presence of 5 mm m ... | 1995 | 8536715 |
| overexpression of extracellular sucrase (sacc) of zymomonas mobilis in escherichia coli. | the extracellular sucrase (sacc) gene of zymomonas mobilis was overexpressed in escherichia coli bl21 using the t7 polymerase expression system. a low cell density induction method was designed to have maximum expression, and the conditions (iptg concentration, ampicillin addition) were optimised to overexpress to the level of more than 60% of the total cellular protein representing sacc protein. | 1995 | 8566709 |
| nucleotide sequence determination and genetic analysis of the bacteroides plasmid, pbi143. | the nucleotide sequence and genetic organization of the bacteroides plasmid pbi143 were determined. the plasmid was 2747 base pairs (bp) and had a g+c content of 41% (genbank accession no. u30316). there were two open reading frames greater than 50 codons and these were designated moba and repa. a 56-bp inverted repeat divided pbi143 into modules with repa and moba in separate regions. there was a marked difference in the g+c content and codon usage for the two regions; repa had 33% g+c and moba ... | 1995 | 8825374 |
| purification, crystallization, and preliminary x-ray diffraction studies of trna-guanine transglycosylase from zymomonas mobilis. | the trna modifying enzyme trna-gnanine transglycosylase (tgt) catalyzes the exchange of guanine in the first position of the anticodon with the quenine precursor 7-aminomethyl-7-deazagnanine. tgt from zymomonas mobilis has been purified by crystallization and further recrystallized to obtain single crystals suitable for x-ray diffraction studies. crystals were grown by vapor diffusion/gel crystallization methods using peg 8,000 as precipitant. macroseeding techniques were employed to produce lar ... | 1996 | 8860000 |
| expression of the escherichia coli pmi gene, encoding phosphomannose-isomerase in zymomonas mobilis, leads to utilization of mannose as a novel growth substrate, which can be used as a selective marker. | wild-type zymomonas mobilis can utilize only three substrates (sucrose, glucose, and fructose) as sole carbon sources, which are largely converted into ethanol and carbon dioxide. here, we show that although d-mannose is not used as a growth substrate, it is taken up via the glucose uniport system (glucose facilitator protein) with a vmax similar to that of glucose. moreover, d-mannose was phosphorylated by a side activity of the resident fructokinase to mannose-6-phosphate. fructokinase was pur ... | 1996 | 8900006 |
| specific spoilage organisms in breweries and laboratory media for their detection. | the gram positive bacteria are generally regarded as the most hazardous beer spoilage organisms in modern breweries, especially the lactobacilli: l. brevis, l. lindneri, l. curvatus, l. casei, l. buchneri, l. coryneformis, l. plantarum, l. brevisimilis, l. malefermentans and l. parabuchneri and the pediococci: p damnosus, p. inopinatus and p. dextrinicus. micrococcus kristinae is the only species within the micrococci relevant to brewing. the gram negative strictly anaerobic bacteria are apparen ... | 1996 | 8913814 |
| genetic and physiological analysis of the lethal effect of l-(+)-lactate dehydrogenase deficiency in streptococcus mutans: complementation by alcohol dehydrogenase from zymomonas mobilis. | ch4ts is a previously isolated recombinant mutant of streptococcus mutans ng8 which produces a thermolabile l-(+)-lactate dehydrogenase (ldh) activity. it does not grow at 42 degrees c under a variety of cultivation conditions. in this study, we show that a batch culture of ch4ts shifted from 30 to 42 degrees c underwent rapid cessation of growth and accelerated cell death. the mutant grew at 42 degrees c in continuous culture under glucose-limiting conditions. under these conditions, lactate pr ... | 1996 | 8926105 |
| development of an arabinose-fermenting zymomonas mobilis strain by metabolic pathway engineering. | the substrate fermentation range of the ethanologenic bacterium zymomonas mobilis was expanded to include the pentose sugar, l-arabinose, which is commonly found in agricultural residues and other lignocellulosic biomass. five genes, encoding l-arabinose isomerase (araa), l-ribulokinase (arab), l-ribulose-5-phosphate-4-epimerase (arad), transaldolase (talb), and transketolase (tkta), were isolated from escherichia coli and introduced into z. mobilis under the control of constitutive promoters th ... | 1996 | 8953718 |
| stabilization of pet operon plasmids and ethanol production in escherichia coli strains lacking lactate dehydrogenase and pyruvate formate-lyase activities. | in the last decade, a major goal of research in biofuels has been to metabolically engineer microorganisms to ferment multiple sugars from biomass or agricultural wastes to fuel ethanol. escherichia coli strains genetically engineered to contain the pet operon (zymomonas mobilis pyruvate decarboxylase and alcohol dehydrogenase b genes) produce high levels of ethanol. strains carrying the pet operon in plasmid (e.g., e. coli b/ploi297) or in chromosomal (e.g., e. coli ko11) sites require antibiot ... | 1996 | 8953729 |
| production of levan, a fructose polymer, using an overexpressed recombinant levansucrase. | 1996 | 8958116 | |
| mutagenesis and crystallographic studies of zymomonas mobilis trna-guanine transglycosylase reveal aspartate 102 as the active site nucleophile. | procaryotic trna-guanine transglycosylase (tgt) catalyzes the posttranscriptional base exchange of the queuine precursor 7-aminomethyl-7-deazaguanine (preq1) with the genetically encoded guanine at the wobble position of trnas specific for asn, asp, his, and tyr. the x-ray structures of zymomonas mobilis tgt and of its complex with preq1 [romier, c., reuter, k., suck, d., & ficner, r. (1996) embo j. 15, 2850-2857] have revealed a specific preq1 binding pocket and allowed a proposal for trna bind ... | 1996 | 8961936 |
| the structure of glucose-fructose oxidoreductase from zymomonas mobilis: an osmoprotective periplasmic enzyme containing non-dissociable nadp. | the organism zymomonas mobilis occurs naturally in sugar-rich environments. to protect the bacterium against osmotic shock, the periplasmic enzyme glucose-fructose oxidoreductase (gfor) produces the compatible, solute sorbitol by reduction of fructose, coupled with the oxidation of glucose to gluconolactone. hence, z mobilis can tolerate high concentrations of sugars and this property may be useful in the development of an efficient microbial process for ethanol production. each enzyme subunit c ... | 1996 | 8994968 |
| cloning and expression of the unique ca2+-atpase from flavobacterium odoratum. | the 60-kda ca2+-atpase from flavobacterium odoratum is kinetically and mechanistically similar to other p-type atpases, suggesting its use as a model system for structure-function studies of ion transport. a portion of the gene was amplified by polymerase chain reaction of genomic dna with degenerate oligonucleotide primers, one based on the n-terminal amino acid sequence of the purified protein and the other based on a consensus sequence for the phosphorylation site of p-type atpases. this gene ... | 1996 | 8617788 |
| ethanol transport in zymomonas mobilis measured by using in vivo nuclear magnetic resonance spin transfer. | for the first time, unidirectional rate constants of ethanol diffusion through the lipid membrane of a microorganism, the bacterium zymomonas mobilis, were determined, thus replacing indirect inferences with direct kinetic data. the rate constants k1 (in to out) were 6.8 +/- 0.4s(-1) at 29 degrees c and 2.7 +/- 0.3s(-1) at 20 degrees c. they were determined by using 1h selective nuclear magnetic resonance spin magnetization transfer. the measurements were done on l-ml cell suspensions. no additi ... | 1996 | 8626306 |
| the role of residues glutamate-50 and phenylalanine-496 in zymomonas mobilis pyruvate decarboxylase. | several enzymes require thiamine diphosphate (thdp) as an essential cofactor, and we have used one of these, pyruvate decarboxylase (pdc; ec 4.1.1.1) from zymomonas mobilis, as a model for this group of enzymes. it is well suited for this purpose because of its stability, ease of purification, homotetrameric subunit structure and simple kinetic properties. crystallographic analyses of three thdp-dependent enzymes [müller, lindqvist, furey, schulz, jordan and schneider (1993) structure 1, 95-103] ... | 1996 | 8645153 |
| continuous ethanol production by zymomonas mobilis and saccharomyces cerevisiae in biofilm reactors. | continuous ethanol fermentations were performed in duplicate for 60 days with zymomonas mobilis atcc 331821 or saccharomyces cerevisiae atcc 24859 in packed-bed reactors with polypropylene or plastic composite-supports. the plastic composite-supports used contained polypropylene (75%) with ground soybean-hulls (20%) and zein (5%) for z. mobilis, or with ground soybean-hulls (20%) and soybean flour (5%) for s. cerevisiae. maximum ethanol productivities of 536 g l-1 h-1 (39% yield) and 499 g l-1 h ... | 1996 | 8652117 |
| crystal structure of trna-guanine transglycosylase: rna modification by base exchange. | trna-guanine transglycosylases (tgt) are enzymes involved in the modification of the anticodon of trnas specific for asn, asp, his and tyr, leading to the replacement of guanine-34 at the wobble position by the hypermodified base queuine. in prokaryotes tgt catalyzes the exchange of guanine-34 with the queuine (.)precursor 7-aminomethyl-7-deazaguanine (preq1). the crystal structure of tgt from zymomonas mobilis was solved by multiple isomorphous replacement and refined to a crystallographic r-fa ... | 1996 | 8654383 |
| the gluemp operon from zymomonas mobilis encodes a high-affinity glutamate carrier with similarity to binding-protein-dependent transport systems. | the nucleotide sequence downstream of the grp gene, encoding the glutamate uptake regulatory protein of zymomonas mobilis, was determined. three clustered genes (glue, glum, and glup) close to ghe grp gene, but on the opposite strand, were identified. these genes encode a high-affinity transport system for glutamate and aspartate. the glup gene product is a polypeptide of 25.4 kda and contains segments with significant similarity to the atp-binding proteins of binding-protein-dependent transport ... | 1996 | 8661924 |
| export of the periplasmic nadp-containing glucose-fructose oxidoreductase of zymomonas mobilis. | glucose-fructose oxidoreductase (gfor) of the gram-negative bacterium zymomonas mobilis is a periplasmic enzyme with the tightly bound cofactor nadp. the preprotein carries an unusually long n-terminal signal sequence of 52 amino acid residues. a sorbitol-negative mutant strain (acm3963) was found to be deficient in gfor activity and was used for the expression of plasmid-borne copies of the wild-type gfo gene or of alleles encoding alterations in the signal sequence of the pre-gfor protein. z. ... | 1996 | 8661942 |
| the relationship between growth enhancement and pet expression in escherichia coli. | the pet operon consists of genes coding for enzymes responsible for ethanol production and consists of pyruvate dehydrogenase and alcohol dehydrogenase ii from the high-performance ethanologen zymomonas mobilis. this article describes the physiological influence of pet expression in escherichia coli b (atcc 11303) in terms of growth rate and overall concentrations of cell mass and catabolic end products achieved under well-defined cultivation conditions that included constant ph and carbon (ener ... | 1996 | 8669901 |
| factors contributing to the loss of ethanologenicity of escherichia coli b recombinants pl0i297 and ko11. | to be economic and to be compatible with modern continuous bioconversion systems, it is imperative that the process organism exhibits an extremely high degree of stability. in the case of ethanol production from lignocellulosic biomass, functional stability of the potential process biocatalyst can be assessed in terms of the capacity to sustain high-performance fermentation during the continuous fermentation of biomass-derived sugars. this investigation employed glucose- or xylose-limited chemos ... | 1996 | 8669902 |
| molecular characterization of the levansucrase gene from the endophytic sugarcane bacterium acetobacter diazotrophicus srt4. | the acetobacter diazotrophicus srt4 gene encoding levansucrase (ec 2.4.1.10) (isda) was isolated from a genomic library. the nucleotide sequence of a 2.3 kb dna fragment sufficient for complementation of a levansucrase-deficient mutant (obtained by ems treatment) was determined. the isda gene (1751 bp) coded for a polypeptide of molecular mass 64.9 kda with an isoelectric point of 5.2. the n-terminal amino acid sequence of the extracellular levansucrase indicated the presence of a precursor prot ... | 1996 | 8704949 |
| 6-phosphogluconate dehydratase from zymomonas mobilis: an iron-sulfur-manganese enzyme. | the enzyme 6-phosphogluconate dehydratase has been isolated in a stable form by a simple one-step procedure using dye ligand chromatography. the role of metal ions in the activity and stability of the enzyme was investigated. as with aconitase and several other dehydratase enzymes, the active site includes an fe4s4 cluster. in addition, the purified enzyme has been shown to contain one manganese ion per subunit, which is also essential for activity. rapid inactivation by superoxide radical was o ... | 1996 | 8728108 |
| identification and characterization of phon-sf, a gene on the large plasmid of shigella flexneri 2a encoding a nonspecific phosphatase. | a gene encoding a nonspecific phosphatase, named phon-sf, was identified on the large virulence plasmid (pmysh6000) of shigella flexneri 2a ysh6000. the phosphatase activity in ysh6000 was observed under high-phosphate conditions. however, it was found that low-phosphate conditions induced a slightly higher level of activity. the nucleotide sequence of the phon-sf region cloned from pmysh6000 possessing the phon-sf gene encoded 249 amino acids with a typical signal sequence at the n terminus. th ... | 1996 | 8755883 |
| ethanol production by a mixed culture of flocculent strains of zymomonas mobilis and saccharomyces sp. | pure and mixed cultures of zymomonas mobilis and saccharomyces sp. were tested for the production of ethanol using sucrose as the carbon source. both strains, isolated from spontaneously fermenting sugar-cane juice, are flocculent and alcohol-tolerant. the best results were obtained using a mixed culture, with a yield of 0.5 g ethanol/g sugar consumed and a volumetric productivity of 1.5 g ethanol l-1 h-1. no levan was produced even if a sucrose-based medium was used. | 1996 | 8766695 |
| overexpression, purification, and generation of a thermostable variant of zymomonas mobilis fructokinase. | the gene encoding fructokinase (ec 2.7.1.4) from zymomonas mobilis has been expressed at high level in escherichia coli by modifying the ribosome binding site using the polymerase chain reaction. a simple two-step purification from extracts of the recombinant cells results in highly purified enzyme suitable for use in fructose determination. using the polymerase chain reaction in mutagenic conditions, a variant of fructokinase was isolated which was more thermostable than the wild type, taking t ... | 1996 | 8776754 |
| the genus sphingomonas: physiology and ecology. | exploitation of the metabolic capabilities of the genus sphingomonas could provide important commercial benefits to biotechnology. recent advances have demonstrated that these organisms have unique abilities to degrade refractory contaminants, to serve as bacterial antagonists to phytopathogenic fungi, and to secrete the highly useful gellan exopolysaccharides. unfortunately, sphingomonas are also animal pathogens and can readily degrade the copper pipes in drinking water distribution systems. t ... | 1996 | 8785434 |
| d-cycloserine biases enrichment for auxotrophic mutants of zymomonas mobilis. | contrary to its effect on rich medium, d-cycloserine showed no bactericidal effect on zymomonas mobilis cells cultured on mineral medium. addition of a mixture of glycine and glutamic acid to the mineral medium restored its bactericidal action. however, mutant enrichments run in these conditions were biased, with mostly methionine mutants isolated. a decrease of the d-cycloserine concentration only reduced the bias. | 1996 | 8810500 |
| cloning and expression of the zymomonas mobilis "production of ethanol" genes in lactobacillus casei. | this study describes the expression of the zymomonas mobilis genes coding for pyruvate decarboxylase (pdc) and alcohol dehydrogenase (adh) in lactobacillus casei 686. to promote transcription, the promoter and ribosome binding site (rbs) from the lactococcus lactis subsp. lactis-derived vector, pmge36e, were inserted upstream of the pdc gene. the former sequences were positioned such that translation of pdc was coupled to translation of an 81-base pair open reading frame terminating within the p ... | 1996 | 8824172 |
| isolation and properties of mutants of zymomonas mobilis deficient in sugar assimilation. | an enrichment method using d-cycloserine was designed for the isolation of spontaneous mutants of zymomonas mobilis deficient in glucose or fructose utilization. the mutants could easily be isolated since they represented 80 to 90% of the population after two and three enrichment cycles. glucokinase and fructokinase activities in the mutants were affected. | 1996 | 16535260 |
| control of glycolytic flux in zymomonas mobilis by glucose 6-phosphate dehydrogenase activity. | glycolytic genes in zymomonas mobilis are highly expressed and constitute half of the cytoplasmic protein. the first four genes (glf, zwf, edd, glk) in this pathway form an operon encoding a glucose permease, glucose 6-phosphate dehydrogenase (g6-p dehydrogenase), 6-phosphogluconate dehydratase, and glucokinase, respectively. each gene was overexpressed from a tac promoter to investigate the control of glycolysis during the early stages of batch fermentation when flux (qco(2)) is highest. almost ... | 1996 | 18624328 |
| development and application of a membrane cyclone reactor for in vivo nmr spectroscopy with high microbial cell densities. | a new bioreactor system has been developed for in vivo nmr spectroscopy of microorganisms under defined physiological conditions. this cyclone reactor with an integrated nmr flow cell is continuously operated in the magnet of a 400-mhz wide-bore nmr spectrometer system. the residence times of medium and cells are decoupled by a circulation-integrated cross-flow microfiltration module to achieve higher cell densities as compared to continuous fermentations without cell retention (increase in cell ... | 1996 | 18629829 |
| crystallization and preliminary x-ray diffraction studies of a cobalt-substituted derivative of the iron-dependent alcohol dehydrogenase from zymomonas mobilis. | the iron-dependent alcohol dehydrogenase from zymomonas mobilis has been crystallized in a form suitable for x-ray diffraction studies. the crystals grew in hanging drops by vapor diffusion, equilibrating with a solution comprising 25-27% methoxypolyethylene glycol 5000 and 1 mm co(2+) in a 0.2 m succinic acid/potassium hydroxide buffer at ph 5.5-5.7 at 281 k. crystals are tetragonal, p4(1)22 (or p4(3)22), with unit-cell dimensions a = b = 125.7, c = 248.1 a. four molecules comprise the asymmetr ... | 1996 | 15299751 |
| the glucanases of cellulomonas. | cellulomonas is a unique bacterium possessing not only the capacity to degrade various carbohydrates, such as starch, xylan and cellulose, but crystalline cellulose as well. it has developed a complex battery of glucanases to deal with substrates possessing such extensive microheterogeneities. some of these enzymes are multifunctional, as well as cross inducible, possessing a multi-domain structure; these enzymes are thought to have arisen by the shuffling of these domains. intergeneric hybrids ... | 1997 | 14538714 |
| transposon mutagenesis and strain construction in zymomonas mobilis. | conjugative or mobilizable plasmids carrying the transposable elements tn5, tn501 or mini mu were readily transferred from escherichia coli donors into zymomonas mobilis recipients with frequencies depending both on donor and recipient strain used. with the exception of pulb113 (rp4::mini mu), all foreign plasmids exhibited high instability in z. mobilis transconjugants under both selective and non-selective conditions. transposition events and consequent mutagenesis occurred readily in z. mobil ... | 1997 | 12455903 |
| effect of acetaldehyde on saccharomyces cerevisiae and zymomonas mobilis subjected to environmental shocks. | the lag phase of saccharomyces cerevisiae subjected to a step increase in temperature or ethanol concentration was reduced by as much as 60% when acetaldehyde was added to the medium at concentrations less than 0.1 g/l. maximum specific growth rates were also substantially increased. even greater proportional reductions in lag time due to acetaldehyde addition were observed for ethanol-shocked cultures of zymomonas mobilis. acetaldehyde had no effect on s. cerevisiae cultures started from statio ... | 1997 | 18629961 |
| simultaneous enzymatic synthesis of gluconic acid and sorbitol: production, purification, and application of glucose-fructose oxidoreductase and gluconolactonase. | with regard to the enzymatic synthesis of sorbitol and gluconic acid, a screening was carried out to identify promising producers of glucose-fructose oxidoreductase (gfor) and gluconolactonase (gl). zymomonas mobilis dsm 473 and rhodotorula rubra dsm 70403 have been selected for the synthesis of gfor and gl, respectively. maximal enzyme production by these organisms has been achieved at d-glucose concentrations of 200 and 150 g/l, respectively. both gfor and gl were purified and characterized wi ... | 1997 | 18576080 |
| optimization of seed production for a simultaneous saccharification cofermentation biomass-to-ethanol process using recombinant zymomonas. | the five-carbon sugar d-xylose is a major component of hemicellulose and accounts for roughly one-third of the carbohydrate content of many lignocellulosic materials. the efficient fermentation of xylose-rich hemicellulose hydrolyzates (prehydrolyzates) represents an opportunity to improve significantly the economics of large-scale fuel ethanol production from lignocellulosic feedstocks. the national renewable energy laboratory (nrel) is currently investigating a simultaneous saccharification an ... | 1997 | 18576087 |
| corn steep liquor as a cost-effective nutrition adjunct in high-performance zymomonas ethanol fermentations. | the ethanologenic bacterium zymomonas mobilis has been demonstrated to possess several fermentation performance characteristics that are superior to yeast. in a recent survey conducted by the national renewable energy laboratory (nrel), zymomonas was selected as the most promising host for improvement by genetic engineering directed to pentose metabolism for the production of ethanol from lignocellulosic biomass and wastes. minimization of costs associated with nutritional supplements and seed p ... | 1997 | 18576088 |
| kinetics of sugar transport and phosphorylation influence glucose and fructose cometabolism by zymomonas mobilis. | the competitive inhibition of fructokinase by glucose has been proposed as the mechanism by which zymomonas mobilis preferentially consumes glucose from mixtures of glucose and fructose and accumulates fructose when growing on sucrose. in this study, incorporation of radioactive fructose into biomass was used as a measure of fructose catabolism. it was determined that the rate of fructose incorporation by z. mobilis cp4 was somewhat lower in the presence of an equimolar concentration of glucose ... | 1997 | 16535690 |
| improved operational stability of cell-free glucose-fructose oxidoreductase from zymomonas mobilis for the efficient synthesis of sorbitol and gluconic acid in a continuous ultrafiltration membrane reactor. | for the continuous, enzymatic synthesis of sorbitol and gluconic acid by cell-free glucose-fructose oxidoreductase (gfor) from zymomonas mobilis, the principal determinants of productivity have been identified. most important, the rapid inactivation of the soluble enzyme during substrate conversion can be avoided almost completely when weak bases such as tris(hydroxymethyl)aminomethan or imidazol are used for the titration of the produced gluconic acid and when 5-10 mm dithiothreitol are added t ... | 1997 | 18634063 |
| bidirectional reaction steps in metabolic networks: i. modeling and simulation of carbon isotope labeling experiments. | the extension of metabolite balancing with carbon labeling experiments, as described by marx et al. (biotechnol. bioeng. 49: 11-29), results in a much more detailed stationary metabolic flux analysis. as opposed to basic metabolite flux balancing alone, this method enables both flux directions of bidirectional reaction steps to be quantitated. however, the mathematical treatment of carbon labeling systems is much more complicated, because it requires the solution of numerous balance equations th ... | 1997 | 18636449 |