Bagasse and vinasse, factory wastes from sugarcane industry as potential substrates for bioethanol production

Bagasse and vinasse are byproducts of sugarcanebased sugar and ethanol production. While bagasse is burned for electricity generation, vinasse is underutilised. The current study determined whether the combination of bagasse with vinasse as the carbon source could produce bioethanol. Lignocellulolytic enzyme-producing fungi were evaluated for pretreatment and saccharification of sugarcane bagasse. The vinasse percentage in growth medium which facilitated the maximum growth of yeast and lignocellulolytic fungi was also determined. The most efficient saccharolytic fungi and fermentative yeast were co-cultured in the bagasse + vinasse medium which facilitated their maximum growth. Ethanol was quantified by High-Performance Liquid Chromatography (HPLC) using ethanol standards. Earliella scabrosa (M14) was the most efficient isolate in pretreatment of sugarcane bagasse with 0.764 U/mL of laccase activity. Aspergillus niger (Fk) was the most efficient isolate in sugarcane bagasse saccharification. Its prolonged incubation period in non-heated/non-washed, washed and heat-treated bagasse types significantly enhanced the bagasse saccharification potential. Results indicated that combining E. scabrosa (M14) with A. niger (Fk) could perform simultaneous pretreatment and saccharification of sugarcane bagasse. A novel finding is that 50 % vinasse + bagasse medium facilitated the maximum growth of lignocellulolytic fungi and fermentative yeast. The highest ethanol yield was given by A. niger-Candida tropicalis co-culture (0.005 %) in heat-treated bagasse + Park’s mineral salt medium whilst Trichoderma sp. (F2)-C. tropicalis (Y4) co-culture showed the highest ethanol yield (0.0031 %) in non-heat treated bagasse + vinasse medium. Therefore, vinasse and bagasse are potential substrates for bioethanol production. Further studies on process optimisation will enhance the final ethanol yields.