17-33: Comparative enzymatic hydrolysis of steam-exploded sugarcane bagasse by supernatants and whole fermentation media of Aspergillus niger and Trichoderma reesei cultivated under solid-state fermentation

Enzymatic conversion of biomass will be a key technology to produce biofuels in the future. However, the major limitation in this process is the high cost of the enzymes. Efforts towards cost reduction have been directed at increasing enzyme production by finding novel microbial strains and efficient fermentation techniques. On-site production of enzymes can help to reduce enzyme costs since there is less need to stabilize the enzyme preparations, avoiding costs with transport and storage. Here, the enzymatic hydrolysis of steam-exploded sugarcane bagasse (SESB) by supernatants and whole fermentation media of Aspergillus niger (3T5B8) and Trichoderma reesei (Rut-C30) cultivated under solid-state fermentation (SSF) was investigated. In addition, the hydrolysis yields were compared with the ones obtained using a commercial cellulase. Both enzyme supernatants and whole fermentation media from the A. niger strain resulted in a more efficient hydrolysis than the ones using the extracts from T. reesei or a commercial cellulase. Glucose conversion using the whole fermentation medium from A. niger, T. reesei and a commercial preparation were 21%, 6% and 17%, respectively. Conversion in terms of reducing sugars reached values up to 41%, 15% and 36%, respectively. In overall, SESB hydrolysis using either supernatant or whole fermentation medium resulted in similar yields, indicating that SSF extraction step could be eliminated. This would be very advantageous towards process cost reduction and also would avoid the production of effluent streams. Therefore, the enzymatic conversion of SESB using the whole fermentation media from SSF can be considered as a potential process configuration.