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

Abstract

Hydrogen (H 2) 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 H 2 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, CO 2, lactate, formate and ethanol, where as on cellulose, the major end-products included hydrogen, acetate, CO 2 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, H 2 production was favored corresponding to acetate synthesis, thereby restricting the carbon flowing to ethanol. During log phase, H 2, CO 2 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.