An Ecological and Economical Strategies of Pretreatment to Explore Biovalorization Potential of Lignocellulosic Agro-Wastes for Ethanol Production

Recent breakthrough in industrial biotechnology offer important opportunities for the utilization of agro-industrial residues like wheat straw, bagasse, peels of Pineapple (Ananas cosmosus), Sweet orange (Citrus sinensis var mosambi) and Litchi (Litchi chinensis). Pretreatment becomes the pivotal step to effectively harness the sugars entrapped within the shield of lignin, which will further make these substrates capable as an ideal substrate for microbial process to produce bioethanol. The major objective of the present investigation was to evaluate the effect of steam explosion, microwave and solar pretreatment on the above lignocellulosic agro-wastes using the chemicals in less concentration for improved yield of reducing sugars. The optimization criterion was the fermentable sugar yields, which were analyzed by HPLC. The best hydrolysis was obtained from the steam explosion pretreatment with 1% HNO3 for bagasse, wheat straw and peels of Litchi chinensis, and with 1% H2SO4 for peels of Ananas cosmosus. A comprehensive account of the above result indicate that 78.2%. 59.56%, 52.15% saccharification (maximum) was obtained when L. chinensis peels, wheat straw and bagasse were steam exploded with 1% HNO3. 75.52% saccharification (maximum) was obtained when A. cosmosus peels were steam exploded with 1% H2SO4. With 1% NaOH steam explosion of Citrus sinensis var mosambi, saccharification was 90.32%. Microwave and solar pretreatment was found suited to only bagasse, as some percentage of glucose, fructose and arabinose was detected in filtrates of 1% HNO3 and distilled water treated bagasse. These results show that an integrated exploitation of these lignocellulosic wastes from agricultural production is economically possible and highly advantageous for ethanol production utilizing suitable microorganism. Results indicate that only a mild pretreatment is necessary in an industrial, economically feasible system.