Heat Shocking of Clostridium Strain P11 to Promote Sporulation and Ethanol Production

Producer gas fermentation is a developing technology that uses acetogenic bacteria for the conversion of CO and H2 into biofuels and commodity chemicals. While different methods have been employed to enhance product concentrations, heat shocking is a physical parameter that is less investigated. This study employs Clostridium strain P11 for the conversion of CO and H2 into ethanol and acetic acid. The strategy for this study was to expose P11 cells to two different temperatures, 75C and 92C, for a short duration (3 min), to induce spore formation and enhance ethanol production. Inocula from these cultures were then transferred into fresh culture media and were compared to cells that were not heat shocked. Spores were observed when a 24 h sample was withdrawn from bottles containing cells that were heated at 75C and 92C. Product concentrations were similar among all treatments (p > 0.05), but cells heat shocked at 92C had a greater yield of ethanol and a lower yield of acetic acid from CO than did the other treatments (p < 0.05). It was observed that heat shocking at 92C also resulted in an increase in gas utilization over the control (p < 0.05). Thus, heat shocking of P11 cells prior to using them for producer gas fermentation enhanced ethanol production. This strategy could be applied to other sporulating acetogenic Clostridial bacteria that have ability to produce solvents autotrophically.