Scientists from CSIR’s National Institute for Interdisciplinary Science and Technology (CSIR-NIIST), Thiruvananthapuram have developed new technique to produce bioethanol from discarded cotton-stalks. The technique uses combination of chemical and biological techniques.
The new technique will help to produce bioethanol, a clean fuel from cotton stalk wastes. Converting the agro-residues such as cotton stalks and wheat and rice husks etc to ethanol reduces the food vs fuel competition.
India has about 9.4 million hectares under cotton cultivation and every hectare generates 2 million tonnes of cotton stalk wastes.
In new technique, cotton stalks first are treated with acid, alkali and different enzymes to breakdown its complex organic polymers. The acid treatment remove hemicellulose, a polymer of cell wall and alkali makes easier to extract lignin, a binding matrix in cell wall, made of complex phenolics.
These treatments exposes cellulose of cotton stalks made of glucose to the action of enzymes. It converts glucose into final product bioethanol by the process of fermentation using a novel yeast strain.
The novel yeast strain used was Saccharomycescerevisiae-RRP-03N, obtained from a rotting wild fruit we found in the Silent Valley National Park, Kerala.
The Saccharomycescerevisiae-RRP-03N yeast performs better than distiller’s yeast strains commonly used in fermenting the cotton stalk hydrolysate. It has glucose conversion efficiency of 76% and it utilised entire glucose in just 24 hours and converted into alcohol. The final alcohol obtained after distillation can be made to fuel grade bioethanol (>99% purity).