Effect of different pretreatments on egyptian sugar-cane bagasse saccharification and bioethanol production

Sugar-cane processing generates large amount of bagasse. Disposal of bagasse is critical for both agricultural profitability and environmental protection. Sugar-cane bagasse is a renewable resource that can be used to produce ethanol. In this study, twelve microbial isolates, five bacteria, four yeasts and three filamentous fungi were isolated from sugar-cane bagasse. Bacterial and yeast isolates were selected for their ability to utilize different sugars and cellulose. Chipped and ground bagasse was subjected to different pretreatment methods; physically through steam treatment by autoclaving at 121 °C and 1.5 bar for 20 min and/or different doses of gamma γ irradiation (50 and 70 Mrad). Autoclaved pretreated bagasse was further biologically treated through the solid state fermentation process by different fungal isolates; F-66, F-94 and F-98 producing maximum total reducing sugars of 18.4., 26.1 and 20.4 g/L, respectively. Separate biological hydrolysis and fermentation (SHF) process for bagasse was done by the two selected fungal isolates; Trichoderma viride F-94 and Aspergillus terreus F-98 and the two yeast isolates identified as Candida tropicalis Y-26 and Saccharomyces cerevisiae Y-39. SHF processes by F-94 and Y-26 produced 226 kg of ethanol/ton bagasse while that of F-98 and Y-39 produced 185 kg of ethanol/ton bagasse.