Factors affecting foaming behavior in cellulase fermentation by Trichoderma reesei Rut C-30

Coupling fermentation with in situ foam fractionation may be beneficial to cellulase production in optimizing oligomer inducer generation, minimizing catabolite repression and reducing cellulase degradation by proteases. In this study, the potential factors that may affect the foaming behavior of broth from Trichoderma reesei Rut C-30 fermentation were examined. These factors included solid (both cell and cellulose) concentrations, cellulase activity and extracellular protein concentration. The loss of cellulase activity caused by the foaming process was minimal. The foamate generation was lower in the presence of higher solids (cell and/or cellulose) concentrations. Cellulase appeared to promote the broth foaming ability but its enrichment ratio was not high (lower than 1.2). The enrichment ratios for the individual component enzymes (beta-glucosidase, endo- and exo-glucanases) were found to be similarly low. None of the cellulase components were likely the primary foaming factors. The foam also carried out cells and cellulose solids. The hydrophobicity of cell surface, studied at various fermentation stages and in both media with and without cellulose, increased as the fermentation approached the stationary phase and then decreased gradually after entering the stationary phase.