METABOLIC CONTROL FOR MICROBIAL FUEL PRODUCTION DURING THERMOPHILIC FERMENTATION OF BIOMASS.

Fermentation of cellulose, pentose or hexose was examined in mono- and co-cultures of Thermoanaerobium brockii HTD4, Methanobacterium thermoautotrophicum YTB, Clostridium thermohydrosulfuricum 39E and Clostridium thermocellum strain LQRI. These species displayed important differences in the range and specificity of substrates metabolized. The three saccharolytic species fermented glucose to ethanol, acetate, lactate and H//2/CO//2 but in quite different proportions. Glucose catabolism in T. brockii was drastically altered by the addition of various electron acceptors which resulted in increased acetate yield and diversion of cellular electron flow from ethanol, lactate and H//2 formation of different reduced end products. Glucose fermentation by T. brockii in co-culture with M. thermoautotrophicum resulted in 2-fold increase in growth rate and formation of acetate and methane as the only significant end products. Ethanol was also fermented to CH//4 and acetate by this co-culture. Ethanol production during cellulose fermentation by C. thermocellum increased 100% in co-culture with C. thermohydrosulfuricum.