PRODUCTION OF GLUCOSE FROM COTTON WASTE BY MICROBIAL EXTRACELLULAR ENZYMATIC HYDROLYSIS

Rajendran R., Rajesh E. M., Arthe R., PSG College of Arts & Science, Coimbatore, India

Introduction. Global warming threats are increasing due to increased emission of Carbon dioxide from utilization of fossil fuels. In light of this issue, search for alternative fuel source which is emission less, continues to be subject of worldwide interest. Much research is poured in finding an alternative bio-based fuel because of positive environmental benefits of biofuels. Potential feedstocks for biofuel production include cellulosic biomass and waste, occurring in abundance outside human food chain which is obtained throughout the year and relatively inexpensive. Cotton is the important cash crop of India and cotton-based textile mills situated in Coimbatore, the Manchester hub of South India, generate huge volumes of cotton waste rich in cellulose. Currently, sugar industry wastes are utilized as raw material for biofuel-bioethanol production.

Waste management is a major problem faced by cotton industries and hence utilization of cotton waste for the production of value-added product bioethanol is a sound method for safe disposal of wastes. Cellulosic wastes can be utilized with help of microbial catalytic cellulase enzyme complex, whose synergistic action depolymerizes cellulose in to fermentable sugars-glucose. Fungi are widely used for cellulase enzyme production. Substrate requires a pretreatment process before being subjected to enzymatic breakdown in order to increase its cellulase susceptibility. Cotton waste, made of 97–98 % cellulose has less or no lignin apart from containing impurities and hence, optimal mild pretreatment is required to make cellulosic cotton fibers present in waste susceptible to cellulase.

Objectives. The project was aimed to recycle cotton waste and produce fermentable sugars out of it which can be fermented with appropriate organism, thereby solving waste management problems and finding of alternative fuel source.

Methodology. Cotton waste was shortened in length mechanically, washed to remove impurities and dried. It was subjected to a range of sulfuric acid and sodium hydroxide pretreatments from 0, 0.5 to 5 % concentrations in the ratio of 3 : 50 in 100 ml flasks and autoclaved for 30 minutes. Acid and alkali insoluble residues of each and every flask was neutralized, dried and used as substrate for enzymatic hydrolysis separately. Cellulase enzyme was produced from Trichoderma reesei (MTCC No. 164). Saccharification of pretreated waste was carried out in 50 mM sodium acetate buffer (pH 5). Substrate-Enzyme concentration was in the ratio of 0.5 : 0.2 (g : ml) in 50 ml of buffer, taken in 100 ml flasks and reaction was carried out at 50 °C for 24 hours. Sugars released upon enzymatic digestion of all flasks were estimated by DNSA method. Fermentable properties of sugars released were checked in terms of alcohol production upon fermentation with Saccharomyces cervisiae.

Results and Conclusion. Sugars released from cotton waste upon enzymatic breakdown, its cellulose conversion percentage and rate of enzymatic hydrolysis increased with increased acid and alkali concentrations used during pretreatment of cotton waste. Acid treatment was found to be efficient than alkali treatment. During fermentation of released sugars, about 12 % of alcohol was detected in the 72 hours old broth. Therefore, cotton waste can be considered as a potential feedstock for the alternative fuel research besides solid waste management.

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Сведения об авторах

Rajendran R., Ph. D., Reader, PG & Research Department of Microbiology, PSG College of Arts & Science, Civil Aerodrome PO, Coimbatore, 641014, India. E-mail

Последние изменения внесены 24.09.08