Biological Pretreatment of Six Lignocellulosic Wastes for Bioethanol Production

The global energy supply depends heavily on a finite supply of fossil fuels, the use of which produces green house gases and pollutants, causing climate change and other environmental problems. Therefore, developing cost effective and environmentally benign alternative energy resources has been gaining importance. Lignocellulosic resources constitute a major portion of agricultural and forestry wastes and it contains approximately 70-80 % carbohydrates. In the present study, an attempt was made to achieve pretreatment method which plays an important role in enhancing the enzymatic saccharification thereby making the whole process economically viable. White rot fungi are well known for production of ligninolytic enzymes which are capable of removing lignin from lignocellulosic substrates. Agricultural wastes, sugarcane baggasse, sweet sorghum, maize stover, groundnut shell, paddy straw and forestry waste, wood chips were used as sources of bioethanol. Pleurotus florida is cultivated by solid state fermentation on these substrates for 28 days. The fruit bodies formed were harvested and their yield, biological efficiency and nutrient content were estimated. The pretreated substrates were further hydrolysed by the cellulolytic enzymes produced by Trichoderma viride. The components of the lytic enzymes, laccase, xylanase, amylase and cellulase were estimated. The sugar rich hydrolysate was further fermented to bioethanol by fermentation processes. Saccharomyces cerevisiae served as fermenting organism. Simultaneous saccharification and fermentation process yielded maximum ethanol in the substrate sweet sorghum. .