Incubation at 25°C prevents acid crash and enhances alcohol production in Clostridium carboxidivorans P7

•Clostridium carboxidivorans P7 was grown autotrophically at 25 and 37°C.•Lower temperatures enhanced production of C4 and C6 alcohols.•Concentrations of butanol and hexanol were among the highest reported for strain P7. Incubation of carboxydotrophs at 37°C provides optimal conditions for their growth. However, a fast accumulation of organic acids, specifically acetate, during the exponential growth phase may result in low alcohol production and substrate consumption due to a phenomenon known as “acid crash”. The present work investigates growth and productivity of Clostridium carboxidivorans P7 at two incubation temperatures. At 37°C the culture was not able to override the “acid crash”, resulting in low ethanol titers (1.56mM). On the other hand, lower metabolic rates at 25°C enhanced ethanol and butanol production (32.1 and 14.5mM, respectively). Moreover, at low temperatures, hexanol and caproic acid were also produced at significant concentrations, 8.21 and 9.02mM respectively, among the highest values reported for P7. Our results demonstrate that production of biofuels with longer carbon chains molecules may be enhanced incubating syngas-fermenting acetogenic bacteria at sub-optimal temperatures.