Growth phase-dependant enzyme profile of pyruvate catabolism and end-product formation in Clostridium thermocellum ATCC 27405 |
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Authors: | Thomas Rydzak David B. Levin Nazim Cicek Richard Sparling |
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Affiliation: | aDeparment of Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2;bDepartment of Biosystems Engineering, University of Manitoba, Winnipeg, Manitoba, Canada R3T 3V6 |
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Abstract: | End-product synthesis and enzyme activities involved in pyruvate catabolism, H2 synthesis, and ethanol production in mid-log (OD600 0.25), early stationary (OD600 0.5), and stationary phase (OD600 0.7) cell extracts were determined in Clostridium thermocellum ATCC 27405 grown in batch cultures on cellobiose. Carbon dioxide, hydrogen, ethanol, acetate and formate were major end-products and their production paralleled growth and cellobiose consumption. Lactate dehydrogenase, pyruvate:formate lyase, pyruvate:ferredoxin oxidoreductase, methyl viologen-dependant hydrogenase, ferredoxin-dependant hydrogenase, NADH-dependant hydrogenase, NADPH-dependant hydrogenase, NADH-dependant acetaldehyde dehydrogenase, NADH-dependant alcohol dehydogenase, and NADPH-dependant alcohol dehydrogenase activities were detected in all extracts, while pyruate dehydrogenase and formate dehydrogenase activities were not detected. All hydrogenase activities decreased (2–12-fold) as growth progressed from early exponential to stationary phase. Alcohol dehydrogenase activities fluctuated only marginally (<45%), while lactate dehydrogenase, pyruvate:formate lyase, and pyruvate:ferredoxin oxidoreductase remained constant in all cell extracts. We have proposed a pathway involved in pyruvate catabolism and end-product formation based on enzyme activity profiles in conjunction with bioinformatics analysis. |
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Keywords: | Clostridium thermocellum Consolidated bioprocessing Pyruvate catabolism Hydrogen synthesis Ethanol synthesis Enzyme activity shift |
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