Hydrogen production and end-product synthesis patterns by Clostridium termitidis strain CT1112 in batch fermentation cultures with cellobiose or α-cellulose

Hydrogen (H2) production and end-product synthesis were characterized in a novel, mesophilic, cellulolytic, anaerobic bacterium, Clostridium termitidis strain CT1112, isolated from the gut of the termite, Nasutitermes lujae. Growth curves, pH patterns, protein content, organic acid synthesis, and H2 production were determined. When grown on 2 g l−1 cellobiose and 2 g l−1 α-cellulose, C. termitidis displayed a cell generation time of 6.5 h and 18.9 h, respectively. The major end-products synthesized on cellobiose included acetate, hydrogen, CO2, lactate, formate and ethanol, where as on cellulose, the major end-products included hydrogen, acetate, CO2 and ethanol. The concentrations of acetate were greater than ethanol, formate and lactate on both cellobiose and α-cellulose throughout the entire growth phase. Maximum yields of acetate, ethanol, hydrogen and formate on cellobiose were 5.9, 3.7, 4.6 and 4.2 mmol l−1 culture, respectively, where as on cellulose, the yields were 7.2, 3.1, 7.7 and 2.9 mmol l−1 culture, respectively. Hydrogen and ethanol production rates were slightly higher in C. termitidis cultured on cellobiose when compared to α-cellulose. Although, the generation time on α-cellulose was longer than on cellobiose, H2 production was favored corresponding to acetate synthesis, thereby restricting the carbon flowing to ethanol. During log phase, H2, CO2 and ethanol were produced at specific rates of 4.28, 5.32, and 2.99 mmol h−1 g dry weight−1 of cells on cellobiose and 2.79, 2.59, and 1.1 mmol h−1 g dry weight−1 of cells on α-cellulose, respectively.