Metabolism of glucose and cellobiose by cellulolytic mesophilic Clostridium sp. strain H10

Abstract

The metabolism of strain H10, a cellulolytic mesophilic Clostridium sp., was studied on glucose and cellobiose as energy and carbon sources. The main products of fermentation of both sugars were acetate, lactate, and ethanol. At low sugar levels, molar growth yields were better for cellobiose than for glucose. In both cases, an inhibition of growth was observed between 1 and 2 g/liter and a total inhibition after the latter concentration. Inhibition was not the result of low pH due to acid formation; growth under static pH conditions was limited in the same way. On the other hand, acetate and lactate had no inhibitory effect when added at concentrations equal to the final titers. Concomitant with the inhibition of growth was a change in metabolic pathways for sugar concentrations between 1 and 2 g/liter, i.e., the production of lactate was higher. After complete inhibition of growth, an accumulation of carbohydrates which were neither glucose nor cellobiose was observed.