Bioconversion of cellulose into fermentable sugars by Saccharomyces cerevisiae cells for the production of ethanol using Cellulolytic fungi isolated from soil

摘要

The fungal species with cellulase activity was isolated from the soil using standard procedures. Two isolates were found to produce relatively high amount of cellulase. The production of cellulase by the two isolates was achieved in liquid shake culture containing Carboxymethyl cellulose as substrate. The filter paper activity and CMCase activity of the two isolates were also compared. The 9th day culture filtrate of the two isolates also exhibited highest activity. Ethanol production was checked in the media containing CMC as substrate after saccharification and fermentation by Saccharomyces cerevisiae cells. The ethanol yield was found to be maximum on the 9th day culture of both the isolates. Thus the current work deals with comparison of cellulase activity of the two isolates and alcohol production of two isolates by simultaneous saccharification and fermentation. Introduction Cellulose is the most abundant renewable natural product in the biosphere. Much of the cellulose in nature exists as waste paper. The potential of cellulose as an alternative energy source has stimulated research into bioconversion process which hydrolyze cellulose to soluble sugars for feedstock in alcoholic fermentations and other industrial processes (Bakare et al., 2005).Study of fungi from the taxonomic point of view is of practical value. Apart from their disease causing nature, their beneficial effects have an increasing role in the industrial field. Fungi are general manager in nutrient recycling department of nature. Fungi have generally been considered the main organisms responsible for decomposition of cellulose. The researchers are trying to discover more cellulolytic fungi and are developing mutant strains to enhance the production of cellulases (Khalid et al., 2006). Bioethanol produced from renewable biomass has received considerable attention in recent years. (Patel et al., 2007). Bioconversion of cellulosic biomass into fermentable sugar for the production of ethanol using cellulose degrading fungi, makes bioethanol production economic, environmental friendly and also renewable. Cellulase is a complex enzyme having chiefly endo and exo1-4 glucanase and β-glucosidase activities. A synergistic action of these enzymes is required for the complete hydrolysis of cellulose (Pothiraj et al., 2006).The Saccharomyces cerevisiae cells have been used in baking and fermenting alcoholic beverages for thousands of years. The ability of yeast to convert sugar into ethanol has been harnessed by the biotechnology industry, which has various uses including ethanol fuel. The fermentation method generally uses three steps: (1) the formation of a solution of fermentable sugars, (2) the fermentation of these sugars to ethanol, and (3) the separation and purification of the ethanol, achieved by distillation methods (Badger, 2002).In recent years, growing attention has been devoted to the conversion of biomass into fuel ethanol, considered the liquid fuel alternative to fossil fuels (Lin and Tanaka, 2005). Bioethanol fermentation is by far the largest scale microbial process. Materials And Methods Isolation Of Cellulolytic FungiMandel’s medium (Patel et al., 2007) was prepared by adding the following reagents (g 1000 ml-1).Urea (0.3 g), (NH)2SO4 (1.4 g), KH2PO4 (2.0 g), CaCl2.2H2O (0.3 g), MgSO4.7H2O (0.3 g), Bactopeptone (1.0 g), Tween 80 ( 0.1 g), Carboxymethyl cellulose(10g). Trace elements: FeSO4.6H2O (5 mg), MnSO4.H2O (16 mg), ZnCl2.2H2O (17mg), CoCl2.6H2O (2 mg).The Mandel’s medium was prepared and its pH was adjusted to 5.0. The conical flasks were plugged with cotton and sterilized at 15 lbs per sq.inch for 20 minutes. Each flask was inoculated with various soil isolate. These flasks were incubated at room temperature for 5 days on a shaker at 125 rpm. After five days, the mycelium was separated by filtration through Whatman filter paper No. 1. The filtrate was used for further analyses of the study.Determination Of Reducing Sugars And Cellulase Act