Hydrogen and volatile fatty acid production during fermentation of cellulosic substrates by a thermophilic consortium at 50 and 60 °C.

The purpose of this study was to characterize the effect of temperature and cellulosic substrates on fermentative metabolites, H(2) production, and community successions in an anaerobic, cellulolytic consortium, TC60. Pyrosequencing analysis indicated that the consortium was predominated by Thermoanaerobacter and Clostridium spp. Metabolite production was analyzed with four cellulosic substrates at 4 kg/m(3). Triplicate cultures of each substrate were incubated at 50 or 60 °C. The main fermentation products (H(2), CO(2), ethanol, and acetate) were monitored over time. The ANOVA model for production rates showed a significant temperature effect (P<0.05) on all products. Increased temperature promoted higher H(2), CO(2), and ethanol yields while acetate yields were only affected prior to 24h of incubation. In addition to individual effects discerned in the model, ANOVA indicated significant interactions between the substrate and temperature. These interactions have not been previously recognized in the literature for cellulolytic and hydrogen-producing microorganisms.