Comparative analysis of bioethanol production involving saccharification by mixed recombinant clostridial enzymes using sugarcane leaves and kans grass as sustainable feed stocks from North-east India

199-210The present study involves bioethanol production from sugarcane (Saccharum officinarum) leaves (SL) and Kans grass (Saccharum spontaneum) (KG), under two separate approaches of fermentation, i) SHF (separate hydrolysis & fermentation) and ii) SSF (simultaneous saccharification & fermentation). The H3PO4-acetone pretreatment strategy was performed for effective lignin removal and enhanced porosity, confirmed by FT-IR (fourier transform infrared spectroscopy) and FESEM (field emission scanning electron microscopy). Saccharification was performed by involving recombinant cellulase GH5 (family 5 of glycoside hydrolase) and hemicellulase GH43 (family 43 of glycoside hydrolase) from Clostridium thermocellum, expressed and isolated from Escherichia coli. Successively, the bioethanol producers Saccharomyces cerevisiae (NCIM 3215) and Candida shehatae (NCIM 3500) were employed. Comparative SHF trials with 1% (w/v) pretreated KG and SL gave bioethanol titre of 0.52 and 0.64 g/L, respectively, whereas SSF experiments resulted in bioethanol titre of 0.8 and 1.0 g/L, respectively at 100 mL shake flask. An increased feedstock concentration of 5% (w/v) KG in shake flask resulted in increased bioethanol titre (4.2 g/L) in SSF. However, the increased substrate concentration of 5% (w/v) SL in individual shake flask resulted in 1.4 fold more bioethanol titre (5.7 g/L) in comparison to KG, and its scale up in bioreactor with 1 L working volume gave bioethanol titre of 11.4 g/L and yield of 0.267 g of bioethanol/g of pretreated SL