activation-independent cyclization of monoterpenoids.biosynthesis of cyclic monoterpenes (c(10)) generally requires cyclization of an activated linear precursor (geranyldiphosphate) by specific terpene cyclases. cyclic triterpenes (c(30)) on the other hand originate from the linear precursor squalene by the action of squalene-hopene cyclases (shcs) or oxidosqualene cyclases (oscs). here, we report on a novel terpene cyclase from zymomonas mobilis (zmo1548-shc) with the unique property to cyclize citronellal to isopulegol. to our knowledge zmo1548- ...201122156419
Engineering yield and rate of reductive biotransformation in Escherichia coli by partial cyclization of the pentose phosphate pathway and PTS-independent glucose transport.Optimization of yields and productivities in reductive whole-cell biotransformations is an important issue for the industrial application of such processes. In a recent study with Escherichia coli, we analyzed the reduction of the prochiral ß-ketoester methyl acetoacetate by an R-specific alcohol dehydrogenase (ADH) to the chiral hydroxy ester (R)-methyl 3-hydroxybutyrate (MHB) using glucose as substrate for the generation of NADPH. Deletion of the phosphofructokinase gene pfkA almost doubled th ...201122002070
Cyclohexane-1,2-dione hydrolase from denitrifying Azoarcus sp. strain 22Lin, a novel member of the thiamine diphosphate enzyme family.Alicyclic compounds with hydroxyl groups represent common structures in numerous natural compounds, such as terpenes and steroids. Their degradation by microorganisms in the absence of dioxygen may involve a C-C bond ring cleavage to form an aliphatic intermediate that can be further oxidized. The cyclohexane-1,2-dione hydrolase (CDH) (EC from denitrifying Azoarcus sp. strain 22Lin, grown on cyclohexane-1,2-diol as a sole electron donor and carbon source, is the first thiamine diphosph ...201121965568
a scalable microfluidic chip for bacterial suspension culture.microfluidic systems could, in principle, enable high-throughput breeding and screening of microbial strains for industrial applications, but parallel and scalable culture and detection chips are needed before complete microbial selection systems can be integrated and tested. here we demonstrate a scalable multi-channel chip that is capable of bacterial suspension culture. the key invention is a multi-layered chip design, which enables a single set of control channels to function as serial peris ...201122030862
Biotransformation of pineapple juice sugars into dietetic derivatives by using a cell free oxidoreductase from Zymomonas mobilis together with commercial invertase.An easy procedure for cell free biotransformation of pineapple juice sugars into dietetic derivatives was accomplished using a commercial invertase and an oxidoreductase from Zymomonas mobilis. First, pineapple juice sucrose was quantitatively converted into glucose and fructose by invertase, thus increasing the concentration of each monosaccharide in the original juice to almost twice. In a second step, glucose-fructose oxidoreductase (GFOR) transformed glucose into gluconolactone, and fructose ...201122112775
Fermentation of Reactive-Membrane-Extracted and Ammonium-Hydroxide-Conditioned Dilute-Acid-Pretreated Corn Stover.Acid-pretreated biomass contains various compounds (acetic acid, etc.) that are inhibitory to fermentative microorganisms. Removing or deactivating these compounds using detoxification methods such as overliming or ammonium hydroxide conditioning (AHC) improves sugar-to-ethanol yields. In this study, we treated the liquor fraction of dilute-acid-pretreated corn stover using AHC and a new reactive membrane extraction technique, both separately and in combination, and then the sugars in the treate ...201122161211
electron transport and oxidative stress in zymomonas mobilis respiratory mutants.the ethanol-producing bacterium zymomonas mobilis is of great interest from a bioenergetic perspective because, although it has a very high respiratory capacity, the respiratory system does not appear to be primarily required for energy conservation. to investigate the regulation of respiratory genes and function of electron transport branches in z. mobilis, several mutants of the common wild-type strain zm6 (atcc 29191) were constructed and analyzed. mutant strains with a chloramphenicol-resist ...201222228443
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