View : 35 Download: 10

NADH availability limits asymmetric biocatalytic epoxidation in a growing recombinant Escherichia coli strain

Title
NADH availability limits asymmetric biocatalytic epoxidation in a growing recombinant Escherichia coli strain
Authors
Buhler B.Park J.-B.Blank L.M.Schmid A.
Ewha Authors
박진병
SCOPUS Author ID
박진병scopus
Issue Date
2008
Journal Title
Applied and Environmental Microbiology
ISSN
0099-2240JCR Link
Citation
vol. 74, no. 5, pp. 1436 - 1446
Indexed
SCI; SCIE; SCOPUS WOS scopus
Abstract
Styrene can efficiently be oxidized to (S)-styrene oxide by recombinant Escherichia coli expressing the styrene monooxygenase genes styAB from Pseudomonas sp. strain VLB120. Targeting microbial physiology during whole-cell redox biocatalysis, we investigated the interdependency of styrene epoxidation, growth, and carbon metabolism on the basis of mass balances obtained from continuous two-liquid-phase cultures. Full induction of styAB expression led to growth inhibition, which could be attenuated by reducing expression levels. Operation at subtoxic substrate and product concentrations and variation of the epoxidation rate via the styrene feed concentration allowed a detailed analysis of carbon metabolism and bioconversion kinetics. Fine-tuned styAB expression and increasing specific epoxidation rates resulted in decreasing biomass yields, increasing specific rates for glucose uptake and the tricarboxylic acid (TCA) cycle, and finally saturation of the TCA cycle and acetate formation. Interestingly, the biocatalysis-related NAD(P)H consumption was 3.2 to 3.7 times higher than expected from the epoxidation stoichiometry. Possible reasons include uncoupling of styrene epoxidation and NADH oxidation and increased maintenance requirements during redox biocatalysis. At epoxidation rates of above 21 μmol per min per g cells (dry weight), the absence of limitations by O2 and styrene and stagnating NAD(P)H regeneration rates indicated that NADH availability limited styrene epoxidation. During glucose-limited growth, oxygenase catalysis might induce regulatory stress responses, which attenuate excessive glucose catabolism and thus limit NADH regeneration. Optimizing metabolic and/or regulatory networks for efficient redox biocatalysis instead of growth (yield) is likely to be the key for maintaining high oxygenase activities in recombinant E. coli. Copyright © 2008, American Society for Microbiology. All Rights Reserved.
DOI
10.1128/AEM.02234-07
Appears in Collections:
엘텍공과대학 > 식품공학전공 > Journal papers
Files in This Item:
NADH.pdf(581.87 kB)Download
Export
RIS (EndNote)
XLS (Excel)
XML


qrcode

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

BROWSE