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 H₂, CO₂, 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 H₂ and 0.7–2.6 mmol ethanol per g cellulose. The rates ranged between 0.01 and 0.2 mmol H₂, 0.03–0.2 mmol CO₂, 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.