Evaluation of enzymatic delignification of rice straw residues for bioethanol production

Abstract

The biomass-based biofuel production from sustainable resources such as lignocellulosics account for the larger alternative energy in the world for achieving zero emissions of greenhouse gas and reduction of global warming. In this study, lignocellulosics, such as rice straw as agricultural residues collected from South 24 Parganas district of West Bengal, have been explored for their potential availability for alternative sources of production of bioethanol. The delignification of rice straw cell wall was performed through alkali pretreatment followed by enzymatic hydrolysis using microorganism Trichoderma reesei, yielded high fermentable sugar for conversion to bioethanol. The efficacy of the delignification process was supported by the structural characteristics of the delignified substrate via scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray fluorescence microscopy and thermogravimetric analysis (TGA). After 240 hours of hydrolysis, the optimum sugar was obtained 135.2 ± 0.45 mg/g from the rice straw. The maximum fermentation efficiency was shown at ~74% in the fed-batch reactor and ~83% in the packed bed reactor using enzyme hydrolysed rice straw at optimal conditions of 33°C and pH = 5.5.