Effect of the type and concentration of cellulose and temperature on metabolite formation by a fermentative thermophilic consortium.

In this study, we hypothesized that anaerobic biodegradation of cellulose is influenced by cellulose type and concentration, temperature, and their interactions. Cellulose biodegradation by an anaerobic consortium was tested in thermophilic batch experiments that combined cellulase action, hydrolysis, and fermentation. Initially, the main constituents in the inocula were Thermoanaerobacter , Clostridium , and Acetivibrio spp. Four types of cellulose and a range of concentrations were used as feedstock with pathways involving hydrolysis and glycolysis to produce H 2 , CO 2 , acetate, and ethanol. Long fibrous cellulose, two types of microcrystalline cellulose, and filter paper squares were tested at several concentrations between 2 and 20 g/l as substrates. The yields ranged between 0.1 and 2.9 mmol H 2 and 0.7–2.6 mmol ethanol per g cellulose. The rates ranged between 0.01 and 0.2 mmol H 2 , 0.03–0.2 mmol CO 2 , and 0.01–0.05 mmol ethanol per g cellulose·h. Statistical analyses indicated that the rates and yields of metabolite production were influenced by two-way interactions between the temperature, type, and concentration of cellulose. The results suggest that two-way interactions between experimental variables may impact the outcomes in cellulose bioconversion studies. • Fermentative biodegradation of four cellulose types was tested at 50, 55 and 60 °C. • The cellulose types comprised long and short fibers and filter paper squares. • Thermoanaerobacter , Clostridium , and Acetivibrio were dominant in the consortium. • Yields and rates were measured for H 2 , CO 2 , ethanol and acetate formation. • Temperature and cellulose type and concentration were two-way interactive variables. [ABSTRACT FROM AUTHOR]