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construction of an escherichia coli k-12 mutant for homoethanologenic fermentation of glucose or xylose without foreign genes.conversion of lignocellulosic feedstocks to ethanol requires microorganisms that effectively ferment both hexose and pentose sugars. towards this goal, recombinant organisms have been developed in which heterologous genes were added to platform organisms such as saccharomyces cerevisiae, zymomonas mobilis, and escherichia coli. using a novel approach that relies only on native enzymes, we have developed a homoethanologenic alternative, escherichia coli strain se2378. this mutant ferments glucose ...200717259366
quantification of lactobionic acid and sorbitol from enzymatic reaction of fructose and lactose by high-performance liquid chromatography.experimental conditions for complete separation and quantification of mixtures containing lactobionic acid, sorbitol, lactose and fructose are discussed for the first time. these mixtures appear in the enzymatic bioconversion of fructose and lactose catalyzed by glucose-fructose oxidoreductase (gfor) and glucono-delta-lactonase (gl) enzymes of zymomonas mobilis cells. the high-performance liquid chromatography (hplc) separation was carried out in a strong cation ion exchange resin (hydrogen form ...200717306812
genetic engineering of zymobacter palmae for production of ethanol from xylose.its metabolic characteristics suggest that zymobacter palmae gen. nov., sp. nov. could serve as a useful new ethanol-fermenting bacterium, but its biotechnological exploitation will require certain genetic modifications. we therefore engineered z. palmae so as to broaden the range of its fermentable sugar substrates to include the pentose sugar xylose. the escherichia coli genes encoding the xylose catabolic enzymes xylose isomerase, xylulokinase, transaldolase, and transketolase were introduced ...200717308178
growth and metabolism in sugarcane are altered by the creation of a new hexose-phosphate sink.an efficient in planta sugarcane-based production system may be realized by coupling the synthesis of alternative products to the metabolic intermediates of sucrose metabolism, thus taking advantage of the sucrose-producing capability of the plant. this was evaluated by synthesizing sorbitol in sugarcane (saccharum hybrids) using the malus domestica sorbitol-6-phosphate dehydrogenase gene (mds6pdh). mature transgenic sugarcane plants were compared with untransformed sugarcane variety q117 by eva ...200717309679
inhibition of pyruvate decarboxylase from z. mobilis by novel analogues of thiamine pyrophosphate: investigating pyrophosphate mimics.replacement of the thiazolium ring of thiamine pyrophosphate with a triazole gives extremely potent inhibitors of pyruvate decarboxylase from z. mobilis, with k(i) values down to 20 pm; this system was used to explore pyrophosphate mimics and several effective analogues were discovered.200717311134
quantifying the metabolic capabilities of engineered zymomonas mobilis using linear programming analysis.the need for discovery of alternative, renewable, environmentally friendly energy sources and the development of cost-efficient, "clean" methods for their conversion into higher fuels becomes imperative. ethanol, whose significance as fuel has dramatically increased in the last decade, can be produced from hexoses and pentoses through microbial fermentation. importantly, plant biomass, if appropriately and effectively decomposed, is a potential inexpensive and highly renewable source of the hexo ...200717349037
a more convenient truth. 200717366694
sampling for metabolome analysis of microorganisms.in the present work we investigated the most commonly applied methods used for sampling of microorganisms in the field of metabolomics in order to unravel potential sources of error previously ignored but of utmost importance for accurate metabolome analysis. to broaden the significance of our study, we investigated different gram-negative and gram-positive bacteria, i.e., bacillus subtilis, corynebacterium glutamicum, escherichia coli, gluconobacter oxydans, pseudomonas putida, and zymononas mo ...200717411014
fermentation of molasses by zymomonas mobilis: effects of temperature and sugar concentration on ethanol production.fermentations utilizing strains of zymomonas mobilis, in place of the traditional yeasts, have been proposed due their ethanol yields being close to theoretical. ethanol production from sugar cane molasses was analyzed under different culture conditions using z. mobilis in batch fermentation. the total reducing sugars (trs) concentrations in the molasses, temperature, agitation and culture time effects were studied simultaneously through factorial design. the best conditions for ethanol producti ...200717420121
expression of glf z.m. increases d-mannitol formation in whole cell biotransformation with resting cells of corynebacterium glutamicum.a recombinant oxidation/reduction cycle for the conversion of d-fructose to d-mannitol was established in resting cells of corynebacterium glutamicum. whole cells were used as biocatalysts, supplied with 250 mm sodium formate and 500 mm d-fructose at ph 6.5. the mannitol dehydrogenase gene (mdh) from leuconostoc pseudomesenteroides was overexpressed in strain c. glutamicum atcc 13032. to ensure sufficient cofactor [nicotinamide adenine dinucleotide (reduced form, nadh)] supply, the fdh gene enco ...200717503033
zymomonas mobilis for fuel ethanol and higher value products.high oil prices, increasing focus on renewable carbohydrate-based feedstocks for fuels and chemicals, and the recent publication of its genome sequence, have provided continuing stimulus for studies on zymomonas mobilis. however, despite its apparent advantages of higher yields and faster specific rates when compared to yeasts, no commercial scale fermentations currently exist which use z. mobilis for the manufacture of fuel ethanol. this may change with the recent announcement of a dupont/broin ...200717522816
crystal structures of trna-guanine transglycosylase (tgt) in complex with novel and potent inhibitors unravel pronounced induced-fit adaptations and suggest dimer formation upon substrate binding.the bacterial trna-guanine transglycosylase (tgt) is a trna modifying enzyme catalyzing the exchange of guanine 34 by the modified base preq1. the enzyme is involved in the infection pathway of shigella, causing bacterial dysentery. as no crystal structure of the shigella enzyme is available the homologous zymomonas mobilis tgt was used for structure-based drug design resulting in new, potent, lin-benzoguanine-based inhibitors. thorough kinetic studies show size-dependent inhibition of these com ...200717524419
metabolic engineering of bacillus subtilis for ethanol production: lactate dehydrogenase plays a key role in fermentative metabolism.wild-type bacillus subtilis ferments 20 g/liter glucose in 48 h, producing lactate and butanediol, but not ethanol or acetate. to construct an ethanologenic b. subtilis strain, homologous recombination was used to disrupt the native lactate dehydrogenase (ldh) gene (ldh) by chromosomal insertion of the zymomonas mobilis pyruvate decarboxylase gene (pdc) and alcohol dehydrogenase ii gene (adhb) under the control of the ldh native promoter. the values of the intracellular pdc and adhii enzymatic a ...200717586670
microwave-assisted hydrolysis of zymomonas mobilis levan envisaging oligofructan production.levan, a polysaccharide from zymomonas mobilis, was hydrolyzed to obtain oligofructans or fructooligosaccharides with a degree of polymerization varying from 4 to 14. fructooligosaccharides (fos) are short chain fructans that beneficially affects the host by selective stimulation of growth and activity of one or a number of bacteria including probiotic bacteria in the colon. the hydrolysis was performed in a microwave oven to shorten the reaction time. the experiments showed that it is possible ...200817604160
single-species microbial biofilm screening for industrial applications.while natural microbial biofilms often consist of multiple species, single-species biofilms are of great interest to biotechnology. the current study evaluates biofilm formation for common industrial and laboratory microorganisms. a total of 68 species of biosafety level one bacteria and yeasts from over 40 different genera and five phyla were screened by growing them in microtiter plates and estimating attached biomass by crystal violet staining. most organisms showed biofilm formation on surfa ...200717653709
structures of dimeric dihydrodiol dehydrogenase apoenzyme and inhibitor complex: probing the subunit interface with site-directed mutagenesis.dimeric dihydrodiol dehydrogenase (dd) catalyses the nicotinamide adenine dinucleotide phosphate (nadp+)-dependent oxidation of trans-dihydrodiols of aromatic hydrocarbons to their corresponding catechols. this is the first report of the crystal structure of the dimeric enzyme determined at 2.0 a resolution. the tertiary structure is formed by a classical dinucleotide binding fold comprising of two betaalphabetaalphabeta motifs at the n-terminus and an eight-stranded, predominantly antiparallel ...200817654552
ethanol production from hydrolysed agricultural wastes using mixed culture of zymomonas mobilis and candida tropicalis.acid, alkaline and enzymatic hydrolysis of agricultural crop wastes were compared for yields of total reducing sugars with the hydrolysates being evaluated for ethanol production using a mixed culture of zymomonas mobilis and candida tropicalis. acid hydrolysis of fruit and vegetable residues gave 49-84 g reducing sugars l(-1) and 29-32 g ethanol l(-1) was then obtained. alkaline hydrolysis did not give significant amount of reducing sugars. enzymatic hydrolysis of fruit and vegetable residues y ...200717657407
asymmetric alkene reduction by yeast old yellow enzymes and by a novel zymomonas mobilis reductase.the genes encoding yeast old yellow enzymes (oye 1, 2, and 3) and nad(p)h-dependent 2-cyclohexen-1-one reductase from zymomonas mobilis (ncr) were expressed separately in escherichia coli. all four recombinant strains reduced the carbon double bond in alpha,beta-unsaturated alkenals and alkenones, however rates and enantio-specificities differed. which of the two possible enantiomers was predominantly formed, was not only dependent on the choice of enzyme but also on the substrate: in addition t ...200717657768
biochemical characterization and phylogenetic analysis of udp-glucose dehydrogenase from the gellan gum producer sphingomonas elodea atcc 31461.sphingomonas elodea atcc 31461 synthesizes in high yield the exopolysaccharide gellan, which is a water-soluble gelling agent with many applications. in this study, we describe the cloning and sequence analysis of the ugdg gene, encoding a udp-glucose dehydrogenase (47.2 kda; udpg-dh; ec 1.1.1.22), required for the synthesis of the gellan gum precursor udp-glucuronic acid. ugdg protein shows homology to members of the udp-glucose/gdp-mannose dehydrogenase superfamily. the neighbor-joining method ...200717668199
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 ...199517791346
growth rate of a non-fermentative escherichia coli strain is influenced by nad+ regeneration.by complementing a non-fermentative escherichia coli (ldha (-) pflb (-)) strain with the recombinant zymomonas mobilis ethanol pathway (pdc, adhb), we evaluated the effect of different levels of enzymatic activity on growth rate demonstrating that there is a direct relationship between anaerobic growth rate and the total specific activity of pyruvate decarboxylase, which is the limiting enzyme of this specific fermentative nad(+) regenerating pathway. this relationship was proved to be useful to ...200717934696
glutamate versus glutamine exchange swaps substrate selectivity in trna-guanine transglycosylase: insight into the regulation of substrate selectivity by kinetic and crystallographic studies.bacterial trna-guanine transglycosylase (tgt) catalyses the exchange of guanine in the wobble position of particular trnas by the modified base preq(1). in vitro, however, the enzyme is also able to insert the immediate biosynthetic precursor, preq(0), into those trnas. this substrate promiscuity is based on a peptide switch in the active site, gated by the general acid/base glu235. the switch alters the properties of the binding pocket to allow either the accommodation of guanine or preq(1). th ...200717949745
ethanol fermentation technologies from sugar and starch feedstocks.this article critically reviews some ethanol fermentation technologies from sugar and starch feedstocks, particularly those key aspects that have been neglected or misunderstood. compared with saccharomyces cerevisiae, the ethanol yield and productivity of zymomonas mobilis are higher, because less biomass is produced and a higher metabolic rate of glucose is maintained through its special entner-doudoroff pathway. however, due to its specific substrate spectrum as well as the undesirability of ...200817964107
an ethanol-tolerant recombinant escherichia coli expressing zymomonas mobilis pdc and adhb genes for enhanced ethanol production from xylose.an ethanol-tolerant mutant, et1, was isolated by an enrichment method from escherichia coli jm109. strains jm109 and et1 were transformed with expression vector pzy507bc containing zymomonas mobilis alcohol dehydrogenase ii (adhb) and pyruvate decarboxylase (pdc) genes, resulting in an ethanol-sensitive recombinant strain jmbc and an ethanol-tolerant recombinant strain, et1bc. alcohol dehydrogenase and pyruvate decarboxylase activities were 24 and 32% lower, respectively, in jmbc than in et1bc. ...200818034308
improvement of p450(bm-3) whole-cell biocatalysis by integrating heterologous cofactor regeneration combining glucose facilitator and dehydrogenase in e. coli.escherichia coli bl21, expressing a quintuple mutant of p450(bm-3), oxyfunctionalizes alpha-pinene in an nadph-dependent reaction to alpha-pinene oxide, verbenol, and myrtenol. we optimized the whole-cell biocatalyst by integrating a recombinant intracellular nadph regeneration system through co-expression of a glucose facilitator from zymomonas mobilis for uptake of unphosphorylated glucose and a nadp(+)-dependent glucose dehydrogenase from bacillus megaterium that oxidizes glucose to gluconola ...200818057930
fermentable metabolite of zymomonas mobilis controls collagen reduction in photoaging skin by improving tgf-beta/smad signaling suppression.solar ultraviolet (uv) irradiation causes damages on human skin and premature skin aging (photoaging). uv-induced reduction of type i collagen in dermis is widely considered primarily induction of wrinkled appearance of photoaging skin. type i procollagen synthesis is reduced under uv irradiation by blocking transforming growth factor-beta (tgf-beta)/smad signaling; more specifically, it is down-regulation of tgf-beta type ii receptor (t beta rii). therefore, preventing uv-induced loss of t beta ...200818060420
analysis of the respiratory chain in ethanologenic zymomonas mobilis with a cyanide-resistant bd-type ubiquinol oxidase as the only terminal oxidase and its possible physiological roles.the respiratory chain of the ethanologenic bacterium zymomonas mobilis was investigated, in which the pyruvate-to-ethanol pathway has been demonstrated to be mainly responsible for nadh oxidation and the tricarboxylic acid cycle is incomplete. membranes from cells cultivated under aerobic or anaerobic growth conditions showed dehydrogenase and oxidase activities for nadh, d-lactate and d-glucose and ubiquinol oxidase activity. intriguingly, the nadh oxidase activity level of membrane fractions f ...200818089934
immobilization of recombinant invertase (re-invb) from zymomonas mobilis on d-sorbitol cinnamic ester for production of invert sugar.the recombinant invertase (re-invb) from zymomonas mobilis was immobilized by adsorption onto the totally cinnamoylated derivative of d-sorbitol. the polymerization and cross-linking of the derivative initially obtained was achieved by irradiation in the ultraviolet region, where this prepolymer shows maximum sensitivity. immobilization of re-invb on this support involves a process of physical adsorption and intense hydrophobic interactions between the cinnamoyl groups of the support and related ...200818237126
nadh dehydrogenase deficiency results in low respiration rate and improved aerobic growth of zymomonas mobilis.the respiratory chain of the ethanol-producing bacterium zymomonas mobilis is able to oxidize both species of nicotinamide cofactors, nadh and nadph. a mutant strain with a chloramphenicol-resistance determinant inserted in ndh (encoding an nadh : coq oxidoreductase of type ii) lacked the membrane nadh and nadph oxidase activities, while its respiratory d-lactate oxidase activity was increased. cells of the mutant strain showed a very low respiration rate with glucose and no respiration with eth ...200818310045
amino acid substitutions of his296 alter the catalytic properties of zymomonas mobilis 10232 levansucrase.his296 of zymomonas mobilis levansucrase (ec 2.4.1.10) is crucial for the catalysis of the transfructosylation reaction. the three-dimensional structures of levansucrases revealed the his296 is involved in the substrate recognition and binding. in this study, nine mutants were created by site-directed mutagenesis, in which his296 was substituted with amino acids of different polarity, charge and length. the substitutions of his296 with arg or trp retained partial hydrolysis and transfructosylati ...200818324341
metabolic engineering of escherichia coli for l-tyrosine production by expression of genes coding for the chorismate mutase domain of the native chorismate mutase-prephenate dehydratase and a cyclohexadienyl dehydrogenase from zymomonas mobilis.the expression of the feedback inhibition-insensitive enzyme cyclohexadienyl dehydrogenase (tyrc) from zymomonas mobilis and the chorismate mutase domain from native chorismate mutase-prephenate dehydratase (phea(cm)) from escherichia coli was compared to the expression of native feedback inhibition-sensitive chorismate mutase-prephenate dehydrogenase (cm-tyra(p)) with regard to the capacity to produce l-tyrosine in e. coli strains modified to increase the carbon flow to chorismate. shake flask ...200818344329
specific ethanol production rate in ethanologenic escherichia coli strain ko11 is limited by pyruvate decarboxylase.modification of ethanol productivity and yield, using mineral medium supplemented with glucose or xylose as carbon sources, was studied in ethanologenic escherichia coli ko11 by increasing the activity of five key carbon metabolism enzymes. ko11 efficiently converted glucose or xylose to ethanol with a yield close to 100% of the theoretical maximum when growing in rich medium. however, when ko11 ferments glucose or xylose in mineral medium, the ethanol yields decreased to only 70 and 60%, respec ...200818349551
heterologous expression of pyruvate decarboxylase in geobacillus thermoglucosidasius.expression of a pyruvate decarboxylase (pdc) pathway in metabolically versatile thermophilic bacteria could create novel ethanologenic organisms, but no suitable thermostable pdc is available. we have demonstrated that pdc from zymomonas mobilis can be expressed in an active form in geobacillus thermoglucosidasius at up to 52 degrees c, while expression of pdc polypeptides up to 54 degrees c was evident from western blotting. by using an unstable lactate dehydrogenase (ldh) mutant of g. thermogl ...200818368298
cloning, solubilization, and characterization of squalene synthase from thermosynechococcus elongatus bp-1.squalene synthase (sqs) is a bifunctional enzyme that catalyzes the condensation of two molecules of farnesyl diphosphate (fpp) to give presqualene diphosphate (pspp) and the subsequent rearrangement of pspp to squalene. these reactions constitute the first pathway-specific steps in hopane biosynthesis in bacteria and sterol biosynthesis in eukarya. the genes encoding sqs were isolated from the hopane-producing bacteria thermosynechococcus elongatus bp-1, bradyrhizobium japonicum, and zymomonas ...200818375558
functional characterization of a putative endoglucanase gene in the genome of zymomonas mobilis.the sequence of the putative endoglucanase gene zmo1086 in the genome of zymomonas mobilis showed a 40% similarity with known bacterial endoglucanase genes. the upstream region of this putative gene revealed the presence of characteristic promoter (-10 and -35 regions) and a shine-dalgarno region. the putative endoglucanase gene was poorly expressed from the native promoter of z. mobilis and therefore the putative endoglucanase gene was cloned and expressed in escherichia coli bl21. the overexpr ...200818414797
a comparison of simple rheological parameters and simulation data for zymomonas mobilis fermentation broths with high substrate loading in a 3-l bioreactor.traditionally, as much as 80% or more of an ethanol fermentation broth is water that must be removed. this mixture is not only costly to separate but also produces a large aqueous stream that must then be disposed of or recycled. integrative approaches to water reduction include increasing the biomass concentration during fermentation. in this paper, experimental results are presented for the rheological behavior of high-solids enzymatic cellulose hydrolysis and ethanol fermentation for biomass ...200818425609
analysis of bacterial community during the fermentation of pulque, a traditional mexican alcoholic beverage, using a polyphasic approach.in this study, the characterization of the bacterial community present during the fermentation of pulque, a traditional mexican alcoholic beverage from maguey (agave), was determined for the first time by a polyphasic approach in which both culture and non-culture dependent methods were utilized. the work included the isolation of lactic acid bacteria (lab), aerobic mesophiles, and 16s rdna clone libraries from total dna extracted from the maguey sap (aguamiel) used as substrate, after inoculati ...200818450312
metabolic regulation analysis of an ethanologenic escherichia coli strain based on rt-pcr and enzymatic activities.a metabolic regulation study was performed, based upon measurements of enzymatic activities, fermentation performance, and rt-pcr analysis of pathways related to central carbon metabolism, in an ethanologenic escherichia coli strain (cce14) derived from lineage c. in comparison with previous engineered strains, this e coli derivative has a higher ethanol production rate in mineral medium, as a result of the elevated heterologous expression of the chromosomally integrated genes encoding pdczm and ...200818471274
identification of yeast and bacteria involved in the mezcal fermentation of agave salmiana.aims: to identify the yeast and bacteria present in the mezcal fermentation from agave salmiana. methods and results: the restriction and sequence analysis of the amplified region, between 18s and 28s rdna and 16s rdna genes, were used for the identification of yeast and bacteria, respectively. eleven different micro-organisms were identified in the mezcal fermentation. three of them were the following yeast: clavispora lusitaniae, pichia fermentans and kluyveromyces marxianus. the bacteria foun ...200818489025
real-time pcr detection of bacteria belonging to the firmicutes phylum.members of the bacterial phylum firmicutes occupy a wide range of habitats and can be either beneficial or detrimental in diverse settings, including food- and beverage-related industries. firmicutes are responsible for the vast majority of beer-spoilage incidents and, as such, they have a substantial financial impact in the brewing industry. rapid detection and identification of a bacterium as a firmicutes is difficult due to widespread genetic transfer and genome reduction resulting in phenoty ...200818501458
development of a versatile shuttle vector for gene expression in geobacillus spp.an improved, versatile shuttle vector has been created for the metabolic engineering of geobacillus spp. as kanamycin is the most thermo-tolerant of commonly used antibiotics, the gene encoding a thermostable kanamycin nucleotidyltransferase, together with the origin of replication from the g. stearothermophilus plasmid pbst1 were cloned into the escherichia coli cloning vector puc18. the resulting vector, named pucg18, replicated in both organisms and could be transformed with an efficiency of ...200818501964
continuous ethanol production and cell growth in an immobilized-cell bioreactor employing zymomonas mobilis.ethanol-producing bioreactors employing cells of zymomonas mobilis attached to glass-fiber pads were operated continuously for as long as 28 days. ethanol production, which is related to bed-associated biomass levels, was found to occur in three distinct phases: an exponential phase, a linear phase, and a "steady-state" phase. after prolonged operation, a bacterial floc developed in the reactor. the maximum effluent ethanol concentration and the maximum volumetric productivity were 6.4% and 152 ...198218546350
fuel alcohol biosynthesis by zymomonas anaerobia: optimization studies.the optimum operating conditions for growth and ethanol production of zymomonas anaerobia atcc 29501 were established. the optimum ph range and temperature were found to be 5.0-6.0 and 35 degrees c, respectively. based on the results obtained from the temperature optimization study, an arrhenius-type temperature relationship for the specific growth rate was developed. the growth and ethanol production of this microbe also have been optimized in terms of concentrations of glucose, essential nutri ...198218546356
ethanol production by immobilized saccharomyces cerevisiae, saccharomyces uvarum, and zymomonas mobilis.saccharomyces cerevisiae nrrl y-2034, s, uvarum nrrl y-1347, and zymomonas mobilis nrrl b-806 each were separately immobilized in a ca-alginate matrix and incubated in the presence of a free-flowing and continuous 1, 3, 5, 10, or 20% (w/w) glucose solution. in general, the yeast cells, converted 100percnt; of the 1, 3, and 5% glucose to alcohol within 48 h and maintained such a conversion rate for at least two weeks. the bacterium converted ca. 90% (w/w) of the 1, 3, and 5% glucose to alcohol co ...198218546408
a filter fermenter-apparatus and control equipment.laboratory equipment for cultivation of microorganisms with the removal of cell-free medium is described. separation is accomplished by filtration through a membrane which is built into a top-driven fermenter. a system is presented which controls the flow rate by automatic cleaning of the filter. flow schemes for batch and continuous fermentations are shown. the filter fermenter is useful when studying continuous culture with feedback of biomass or processes where growth or product formation rat ...198218548501
properties and application of immobilized beta-d-glucosidase coentrapped with zymomonas mobilis in calcium alginate.the enzyme beta-d-glucosidase has been immobilized on concanavalin a-sepharose to give a maximum loading of 2050 units/g dry weight of support material. the immobilized beta-d-glucosidase was also entrapped within calcium alginate gel spheres with apparently only 35% retention of activity when assayed with 10mm cellobiose. however, it was discovered that, unlike the immobilized enzyme, the entrapped immobilized enzyme was not subject to substrate inhibition up to 100mm cellobiose, suggesting tha ...198318548572
continuous simultaneous saccharification and fermentation of starch using zymomonas mobilis.a continuous process involving simultaneous saccharification and fermentation of liquefied starch has been developed using zymomonas mobilis. amyloglucosidase retention and cell recycle have been effected by using an amicon hollow-fiber membrane system with a mw cutoff of 5000. relatively high productivities of up to 60 g l(-1) h(-1) have been achieved at ethanol concentrations of 60-65 g/l. the system also offers the potential for reduced enzyme requirements for saccharification.198318548684
effects of temperature and ethanol concentration on the maintenance and yield coefficient of zymomonas mobilis. 198318551448
ethanol production by zymomonas mobilis in fed-batch fermentations.the production of ethanol by zymomonas mobilis nrrl b-4286 was studied in fed-batch cultures. initial percent (w/v) glucose, rate of feed, and quantity of 50%; (w/v) glucose feed were varied. glucose inhibition of growth rate occurred at concentrations greater than 8% (w/) feed was begun after 4 h incubation. feed volume was ca. 36%; of starting batch volume to get ca. 10%; (w/v) ethanol at harvest. the range of feed rates studied varied from 16%; batch volume/h (glucose concentration increased ...198418551733
influence of the presence of zymomonas anaerobia on the conversion of cellobiose, glucose, and xylose to ethanol by clostridium saccharolyticum.to convert sugar mixtures containing cellobiose, glucose, and xylose to ethanol in a single step, the possibility of using a coculture consisting of clostridium saccharolyticum and zymomonas anaerobia was studied. in monoculture, c. saccharolyticum utilized all three sugars; however, it preferentially utilized glucose and produced acetic acid in addition to ethanol. the formation of acetic acid from the metabolism of glucose inhibited the growth of c. saccharolyticum and, consequently, the utili ...198418553484
cell immobilization in kappa-carrageenan for ethanol production.a combination of extended monod kinetics and the diffusional equation was used for evaluating the effectiveness factor of entrapped immobilized cells. based on the kinetics of zymomonas mobilis reported in the literature, the numerical results have revealed that the problem of mass transfer diffusional restrictions can be neglected by using small beads (1 mm in diameter) with a corresponding cell loading up to 276 g/l gel. on the basis of the numerical results obtained, the application of immobi ...198518553626
preparation and characterization of immobilized growing cells of zymomonas mobilis for ethanol production.zymomonas mobilis cells were entrapped in k. carrageenan. growth was observed with the immobilized cell preparation. the kinetic and yield parameters for the conversion of fructose to ethanol were nearly identical to free cells. the same preparation of immobilized cells was used in six repeated batch runs and at the end sixth-batch fructose was converted to ethanol more rapidly and efficiently with ethanol productivity of 14 g/l h and 96% conversion of fructose. the effect of high fructose and e ...198518553669
continuous production of ethanol from fructose by immobilized growing cells of zymomonas mobilis.immobilized growing cells of zymomonas mobilis were found to ferment rapidly and efficiently media containing 100 g/l fructose in a continuous reactor. a volumetric ethanol productivity of 94.8 g/l h was achieved at a substrate conversion of 75.5%. with 97% conversion of substrate the productivity was 28.4 g/l h. at fructose concentrations of 150 and 200 g/l substrate and product inhibitions limited the performance of the reactor. ethanol production was constant over a period of 55 days.198518553716
filament formation and ethanol production by zymomonas mobilis in adsorbed cell bioreactors.zymomonas mobilis immobilized on microporous ion exchange resins has previously been shown to allow the attainment of high ethanol productivities in packed-bed bioreactors. the formation of bacterial filaments after several days of continuous operation, however, had resulted in excessive pressure increases across the reactor bed. the present work examines techniques for controlling filament formation by z. mobilis in two reactor sizes (161 ml and 7.85 l) and a feed glucose concentration of 100 g ...198518553718
mathematical modelling of growth and substrate conversion of zymomonas mobilis at 30 and 35 degrees c.zymomonas mobilis was grown in continuous cultures at 30 and 35 degrees c. the specific substrate consumption rates at 35 degrees c were higher than those at 30 degrees c. an unstructured mathematical model based on the linear equation for substrate consumption provided a statistically adequate description for cultures grown at 35 degrees c but not for cultures grown at 30 degrees c. a structured two-compartment model described growth and substrate consumption well at both temperatures. some the ...198518553768
simultaneous saccharification/fermentation with zymomonas mobilis. 198618553851
ethanol production from starch by a coimmobilized mixed culture system of aspergillus awamori and zymomonas mobilis.the production of ethanol from starch by a coimmobilized mixed culture system of aerobic and anaerobic microorganisms in ca-alginate gel beads was investigated. the mold aspergillus awamori was used as an aerobic amylolytic microorganism and an anaerobic bacterium, zymomonas mobilis, as an ethanol producer. by controlling the mixing ratio of the microorganisms in the inoculum size, a desirable coimmobilized mixed culture system, in which the aerobic mycelia grew on and near the oxygen-rich surfa ...198618555292
anaerobic calorimetry of zymomonas mobilis using a heat-flux sensor.a relatively simple and inexpensive anaerobic calorimeter was designed and evaluated by using a hy-cal engineering bi-7 bidirectional heat-flux sensor to measure heat output from magnetically stirred i-l flask fermentations. the production of ethanol and cumulative heat output by zymomonas mobilis were both linearly proportional to glucose concentrations up to 160 g/l.198618555293
the inhibition of the maximum specific growth and fermentation rate of zymomonas mobilis by ethanol.the inhibition of the maximum specific growth and fermentation rate of zymomonas mobilis by ethanol was studied in turbidostat cultures at constant and stepwise changed ethanol concentrations. up to 50 g/l ethanol, the inhibition kinetics can be approximated by a linear relationship between the specific growth rate and the ethanol concentration. above this level, deviations from this linearity are observed. the specific fermentation rates were less inhibited by ethanol than was the specific grow ...198618555360
effect of temperature and ph on immobilized zymomonas mobilis for continuous production of ethanol.the effects of temperature and inlet ph of the medium on the ethanol productivity and activity of the immobilized z. mobilis cells during continuous fermentation of glucose have been studied at various temperatures and ph. on changing the temperature from one steady state level to a new one, 6-8 h were required in order to fully experience the effect of a change in temperature; whereas 8-20 h were required on changing the ph. the optimum temperature of 37 degrees c and a broad ph range of 4.4-6. ...198618555399
kinetics of batch fermentations for ethanol production with zymomonas mobilis growing on jerusalem artichoke juice.a flocculent strain of zymomonas mobilis was used for ethanol production from jerusalem artichoke juice containing 113-245 g/l sugar in batch fermentation. the kinetic and yields parameters are calculated using a new method based on polynomial equations for the variation of biomass, ethanol, and sugar concentrations with time. the results show that. z. mobilis can convert rapidly and efficiently jerusalem artichoke juice to ethanol. when a sugar concentration of 248 gl was used, 100 g/l ethanol ...198618555403
fermentation kinetics of zymomonas mobilis at high ethanol concentrations: oscillations in continuous cultures.substrate-limited continuous culture results at 47 g/l ethanol show that the maintenance factor and the yield factor of an unstructured maintenance model are lower compared to the values at 23 g/l ethanol. computing the results according to a structured two-compartment model predicts an enhanced turnover rate of the k-compartment (rna fraction) by ethanol, resulting in a lower steady-state amount of k-compartment. this is in agreement with experimentally determined rna fractions. the parameters ...198618555405
zymomonas mobilis as catalyst for the biotechnological production of sorbitol and gluconic acid.the conversion of glucose and fructose into gluconic acid (ga) and sorbitol (sor) was conducted in a batch reactor with free (ctab-treated or not) or immobilized cells of zymomonas mobilis. high yields (more than 90%) of gluconic acid and sorbitol were attained at initial substrate concentration of 600 g/l (glucose plus fructose at 1:1 ratio), using cells with glucose-fructose-oxidoreductase activity of 75 u/l. the concentration of the products varied hyperbolically with time according to the eq ...200618563654
improving fermentation performance of recombinant zymomonas in acetic acid-containing media.in the production of ethanol from lignocellulosic biomass, the hydrolysis of the acetylated pentosans in hemicellulose during pretreatment produces acetic acid in the prehydrolysate. the national renewable energy laboratory (nrel) is currently investigating a simultaneous saccharification and cofermentation (sscf) process that uses a proprietary metabolically engineered strain of zymomonas mobilis that can coferment glucose and xylose. acetic acid toxicity represents a major limitation to biocon ...199818575986
conditions that promote production of lactic acid by zymomonas mobilis in batch and continuous culture.this study documents the similar ph-dependent shift in pyruvate metabolism exhibited by zymomonas mobilis atcc 29191 and atcc 39676 in response to controlled changes in their steady-state growth environment. the usual high degree of ethanol selectivity associated with glucose fermentation by z. mobilis is associated with conditions that promote rapid and robust growth, with about 95% of the substrate (5% w/v glucose) being converted to ethanol and co2, and the remaining 5% being used for the syn ...199818575987
cofermentation of glucose, xylose, and arabinose by mixed cultures of two genetically engineered zymomonas mobilis strains.cofermentation of xylose and arabinose, in addition to glucose, is critical for complete bioconversion of lignocellulosic biomass, such as agricultural residues and herbaceous energy crops, to ethanol. a factorial design experiment was used to evaluate the cofermentation of glucose, xylose, and arabinose with mixed cultures of two genetically engineered zymomonas mobilis strains (one ferments xylose and the other arabinose). the ph range studied was 5.0-6.0, and the temperature range was 30-37 d ...199818575998
continuous culture studies of xylose-fermenting zymomonas mobilis.the continuous cofermentation performance of xylose-fermenting zymomonas mobilis at 30 degrees c and ph 5.5 was characterized using a pure-sugar feed solution that contained 8 g/l glucose and 40 g/l xylose. successful chemostat start up resulted in complete utilization of glucose and greater than 85% utilization of xylose, but was only reproducibly achieved using initial dilution rates at or less than 0.04/h; once initiated, cofermentation could be maintained at dilution rates of 0.04 to 0.10/h. ...199818576004
production of ethanol from starch by co-immobilized zymomonas mobilis-glucoamylase in a fluidized-bed reactor.the production of ethanol from starch was studied in a fluidized-bed reactor (fbr) using co-immobilized zymomonas mobilis and glucoamylase. the fbr was a glass column of 2.54 cm in diameter and 120 cm in length. the z. mobilis and glucoamylase were co-immobilized within small uniform beads (1.2-2.5 mm diameter) of kappa-carrageenan. the substrate for ethanol production was a soluble starch. light steep water was used as the complex nutrient source. the experiments were performed at 35 degrees c ...199818576011
simultaneous enzymatic synthesis of gluconic acid and sorbitol. continuous process development using glucose-fructose oxidoreductase from zymomonas mobilis.the production of sorbitol and gluconic acid by isolated glucose-fructose oxidoreductase (gfor) from zymomonas mobilis has been studied in a convective, 100-ml loop reactor with tangential ultrafiltration. using a dilution rate of 0.04/h and 5 ku/l gfor, substrate conversion (3 m sugar) in a single stage was >85%, and productivities of 126 g sorbitol/(l x d) were obtained. at a constant recycle rate (3/min) and a membrane area of 50 cm2, the dilution rates (and thus productivities) were however ...199818576049
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 ...199718576080
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 ...199718576087
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 ...199718576088
mathematical modeling of ethanol production by immobilized zymomonas mobilis in a packed bed fermenter.a mathematical model which describes ethanol production in a packed bed fermenter containing. zymomonas mobilis entrapped in small spheres of calcium alginate within a packed bed fermenter has been developed. the equations combine simultaneous diffusion and reaction as well as a complex flow pattern to calculate glucose and ethanol profiles in the column type reactor. as part of the study, diffusivity values for glucose and ethanol in cell-loaded calcium alginate were determined. also a freecell ...198718576429
fermentation kinetics of zymomonas mobilis near zero growth rate.the fermentation kinetics zymomonas mobilis were studied near zero growth rate in fed-batch cultures and continuous cultures with complete cell recycle. the results show the ethanol enhances that specific substrate conversion rate under these conditions. the maximum achievable ethanol concentration in continuous cultures with cell recycle (66 g/l) was significantly lower than in fed-batch cultures (100 g/l). the results indicate that growth-rate-independent metabolism is not instantaneous and ca ...198718576479
continuous production of ethanol with zymomonas mobilis growing on jerusalem artichoke juice. 198718576518
effect of intraparticle diffusion in ethanol fermentation by immobilized zymomonas mobilis. 198818584650
liquid residence time distributions in immobilized cell bioreactors.previous work has demonstrated that high ethanol productivities can be achieved using yeast or bacterial cells adsorbed onto the surface of ion exchange resin in vertical packed bed bioreactors. the present work quantitatively characterizes the overall degree of backmixing in such reactors at two scales of operation: 2.0 and 8.0 l. stimulus-response experiments, using two solvents (2,3-butanediol and 2-ethoxyethanol) as tracers, were performed to measure the liquid phase residence time distribut ...198918587958
growth inhibition of zymomonas mobilis atcc 10988 by ammonium ions. 198918588103
immobilized cell biocatalyst activation and pseudo-steady-state behavior: model and experiment.an intrinsic, unstructured model has been utilized to describethe startup dynamics of a continuous caalginate-immobilized zymomonas mobilis (atcc 10988) fermentation. this model predicts, at least qualitatively, transients in the fermenter effluent glucose, ethanol, and biomass concentrations as well as radial gradients in immobilized-cell concentration and activity within the gelbiocatalysts. predicted intrabiocatalyst gradients in immobilized-cell specific growth rate were used to calculate th ...199018592556
a structured kinetic model for zymomonas mobilis atcc10988.the inhibitory effects of glucose and ethanol on zymomonas mobilis atcc10988 were isolated through kinetic analysis of transient batch fermentation data. growth of z. mobilis was inhibited above a glucose concentration of 80 g/l. growth was mildly inhibited by ethanol to 50 g/l, and severely inhibited above this concentration. specific rates of ethanol production and glucose uptake were essentially invariant during batch fermentation. a structured kinetic model was developed, by way of augmentat ...199018597261
a new biosensor for specific determination of glucose or fructose using an oxidoreductase of zymomonas mobilis.cells of zymomonas mobilis were permeabilized with toluene in order to utilize the enzymes, glucose-fructose oxidoreductase and gluconolactonase, inside the intact cells. permeabilized cells were immobilized in a gelatin membrane, and a whole cell enzyme electrode was constructed by fixing the membrane on ph electrode. the biosensor developed was used for specific determination of glucose or fructose by detecting the production rate of hydrogen ion. optimum conditions for biosensor response were ...199018597267
tubular bioreactors: case study of bioreactor performance for industrial production and scientific research.application of bioreactors is dominated by industrial production with the consequence that bioreactors also for scientific purposes are mainly used following an empiric pragmatic approach. for the sake of a breakthrough in biotechnology in general, and especially for advanced process development, a more systematic approach is emphasized here. this methodology in bioreactor performance studies is explained and the meaning clarified in a case study of a new type of tubular bioreactor. the central ...199118597337
effect of alteration of the acetic acid synthesis pathway on the fermentation pattern of escherichia coli.the glucose metabolism of an escherichia coli strain bearing mutations abolishing both acetyl phosphotransferase (pta) and acetate kinase (ack) activities was studied under aerobic and anaerobic conditions. these studies were conducted in a complex medium with the mutant carrying no plasmid, the mutant carrying the common cloning vector puc19, and the mutant carrying a plasmid bearing the "pet" operon that encodes zymomonas mobilis pyruvate decarboxylase and alcohol dehydrogenase activities. the ...199118600733
a new biosensor for specific determination of sucrose using an oxidoreductase of zymomonas mobilis and invertase.a new biosensor for specific determination of sucrose was developed using an oxidoreductase of zymomonas mobilis and invertase. cells of z. mobilis were permeabilized with toluene in order to utilize the enzymes of glucose-fructose oxidoreductase and gluconolactonase inside the intact cells. permeabilized cells and invertase were coimmobilized in a gelatin membrane, and a whole cell enzyme electrode was constructed by fixing the membrane on a ph electrode. the production of hydrogen ion was dete ...199118600754
batch fermentation kinetics of sugar beet molasses by zymomonas mobilis.a new osmotolerant mutant strain of zymomonas mobilis was successfully used for ethanol production from beet molasses. addition of magnesium sulfate to hydrolyzed molasses allowed repeated growth without the need of yeast extract addition. the kinetics and yields parameters of fermentation on media with different molasses concentrations were calculated. the anabolic parameters (specific growth rate, mu, and biomass yield, y(x/s)) were inhibited at elevated molasses concentrations while the catab ...199118600764
influence of expression of the pet operon on intracellular metabolic fluxes of escherichia coli.fermentation patterns of escherichia coli hb101 carrying plasmids expressing cloned genes of zymomonas mobilis pyruvate decarboxylase (pdc) and alcohol dehydrogenase li (adh) were determined in glucose-limited complex medium in ph-controlled anaerobic batch cultivations. time profiles of glucose, dry cell weight, succinate, formate, acetate, and ethanol were determined, as were the activities of adh and pdc. fluxes through the central carbon pathways were calculated for each construct utilizing ...199218600887
continuous production of gluconic acid and sorbitol from jerusalem artichoke and glucose using an oxidoreductase of zymomonas mobilis and inulinase.gluconic acid and sorbitol were simultaneously produced from glucose and jerusalem artichoke using a glucose-fructose oxidoreductase of zymomonas mobilis and inulinase. inulinase was immobilized on chitin by cross-linking with glutaraldehyde. cells of z. mobilis permeabilized with toluene were coimmobilized with chitin-immobilized inulinase in alginate beads. the optimum amounts of both chitin-immobilized inulinase and permeabilized cells for coimmobilization were determined, and operational con ...199218600950
fermentation of sweet whey by ethanologenic escherichia coli.whey, an abundant byproduct of the dairy industry, contains large amounts of protein and lactose which could be used for fuel ethanol production. we have investigated a new organism as a candidate for such fermentations: recombinant escherichia coli containing the genes encoding the ethanol pathway from zymomonas mobilis. the highest level of ethanol achieved, 68 g/l, was produced after 108 hours in luria broth containing 140 g lactose/l. fermentations of lower lactose concentrations were comple ...199218601042
transport and intracellular accumulation of acetaldehyde in saccharomyces cerevisiae.the rate of acetaldehyde efflux from yeast cells and its intracellular concentration were studied in the light of recent suggestions that acetaldehyde inhibition may be an important factor in yeast ethanol fermentations. when the medium surrounding cells containing ethanol and acetaldehyde was suddenly diluted, the rate of efflux of acetaldehyde was slow relative to the rate of ethanol efflux, suggesting that acetaldehyde, unlike ethanol, may accumulate intracellularly. intracellular acetaldehyd ...199318609643
a model system for a fluorometric biosensor using permeabilized zymomonas mobilis or enzymes with protein confined dinucleotides.using permeabilized zymomonas mobilis or glucose-fructose oxidoreductase isolated from this microorganism a model system for biosensors with a protein confined nadp(h) cofactor for the determination of glucose, fructose, gluconolactone, and sorbitol was developed. either permeabilized microorganisms containing the oxidoreductase or the pure enzyme were confined via membrane separation in a small measuring chamber, that was integrated into a flow injection analysis system (fia). the measuring pri ...199318613024
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 ...199418615609
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 ...199418618690
[optimization of fuel ethanol production from kitchen waste by plackett-burman design].kitchen garbage was chosen to produce ethanol through simultaneous saccharification and fermentation (ssf) by zymomonas mobilis. plackett-burman design was employed to screen affecting parameters during ssf process. the parameters were divided into two parts, enzymes and nutritions. none of the nutritions added showed significant effect during the experiment, which demonstrated that the kitchen garbage could meet the requirement of the microorganism without extra supplementation. protease and gl ...200818624223
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 ...199618624328
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 ...199618629829
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 ...199718629961
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 ...199718634063
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 ...199718636449
experimental investigation and modeling of oscillatory behavior in the continuous culture of zymomonas mobilis.the mechanism causing oscillation in continuous ethanol fermentation by zymomonas mobilis under certain operating conditions has been examined. a new term, "dynamic specific growth rate," which considers inhibitory culture conditions in the recent past affecting subsequent cell behavior, is proposed in this article. based on this concept, a model was formulated to simulate the oscillatory behavior in continuous fermentation of zymomonas mobilis. forced oscillation fermentation experiments, in wh ...199718636614
high-solid enzymatic hydrolysis and fermentation of solka floc into ethanol.to lower the cost of ethanol distillation of fermentation broths, a high initial glucose concentration is desired. however, an increase in the substrate concentration typically reduces the ethanol yield because of insufficient mass and heat transfer. in addition, different operating temperatures are required to optimize the enzymatic hydrolysis (50 degrees c) and fermentation (30 degrees c). thus, to overcome these incompatible temperatures, saccharification followed by fermentation (sff) was em ...200818667854
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