RT Journal Article SR Electronic(1) A1 Vancanneyt, Marc A1 De Vos, Paul A1 Vennens, Linda A1 De Ley, JozefYR 1990 T1 Lactate and ethanol dehydrogenase activities in continuous cultures of Clostridium thermosaccharolyticum LMG 6564 JF Microbiology, VO 136 IS 10 SP 1945 OP 1951 DO https://doi.org/10.1099/00221287-136-10-1945 PB Microbiology Society, SN 1465-2080, AB The pattern of ethanol and lactate formation by continuous cultures of Clostridium thermosaccharolyticum LMG 6564 under glucose limitation is affected by culture conditions such as pH and dilution rate. NADH- and NADPH-mediated lactate dehydrogenase (LDH; EC 1.1.1.27) and alcohol (ethanol) dehydrogenase (ADH; EC 1.1.1.1 and EC 1.1.1.2) activities were measured in cell extracts from continuous cultures grown under different conditions. In conditions of high product formation, the NADH-mediated reaction was higher than the NADPH-mediated reaction for both LDH and ADH. LDH showed an absolute requirement for fructose 1,6-bisphosphate (FBP). Both NADH- and NADPH-linked LDH reactions were cytoplasmic, not sensitive to oxygen, and had a pH optimum of 6·0–6·5; the temperature optimum was 55–60 °C. The reverse reaction (lactate oxidation) could not be demonstrated. ADH activity was found in the particulate fraction of the cell lysate and was sensitive (not completely, but irreversibly) to oxygen. The temperature and pH optima were 43 °C, pH 7·0 and 45 °C, pH 8·8 for the NADH- and NADPH-mediated reactions, respectively. The production of at least two different ADHs is likely. LDH and ADH seemed to be regulated at the level of enzyme synthesis (direct correlation between the in vitro activities and the lactate and ethanol yields in the culture) with a second regulation of LDH by FBP at the reaction level., UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-136-10-1945