A review on bioprocessing of paddy straw to ethanol using simultaneous saccharification and fermentation

Paddy straw is one of the largely produced crop residues obtained after harvesting the rice crop. Environmentally unsustainable disposal of paddy straw such as uncontrolled digestion and stubble burning leads to health threats to living beings and climate change via large greenhouse gas emissions. Presence of high hexose (C6) and pentose (C5) sugars in paddy straw makes it potentially valuable source for ethanol production through hydrolysis of polysaccharides into simple sugars followed by fermentation. Utilizing these fermentable sugars of paddy straw is not only an environmentally sustainable management of paddy straw but it also generates renewable and carbon neutral energy. Simultaneous saccharification and fermentation (SSF) is one of the well-known techniques, which enhances the ethanol productivity and yield by reducing process time and preventing feedback inhibition of cellulases, respectively. The present review article focuses on the availability and ethanol potential of paddy straw in the earlier part. Further, bioprocessing of paddy straw into ethanol using SSF, environmental sustainability, economic evaluation, key challenges and solutions for ethanol production are addressed in the later part.