Production of Cellulase by Aspergillus niger on natural and pretreated lignocellulosic wastes

摘要

Growth of Aspergillus niger on Czapek-dox medium supplemented with native lignocellulosics like Sawdust, wheat straw, Sugarcane baggage and Ricebran used for the production of cellulase by A.niger. Of these Czapek-dox medium with 0.5% Wheat straw had yielded more cellulase, FPase (2.9 U/ml), CMCase (2.9 U/ml) and β-glucosidase (0.93 U/ml) after 14-days of incubation. The lignocellulosics after pre-treatment improved cellulase production. Among the treated substrates, Czapek-dox medium with 0.5% saw dust had yielded FPase (6.3 U/ml), CMCase (7.2 U/ml) after 7-days of incubation and the medium with treated rice bran produced β-glucosidase of 1.04 U/ml after 21-days of incubation. Introduction Cellulose is the major polysaccharide constituent of plant cell wall and one of the most abundant available organic compounds in the biosphere and its estimated synthesis rate of 10 10 tones per year (Schlesinger, 1991; Singh and Hayashi, 1995; Lynd et al., 2002). Cellulose-rich plant biomass is one of the foreseeable and sustainable sources of fuel, animal feed and feed stock for chemical synthesis (Bhat, 2000). The utilization of cellulosic biomass continues to be a subject of worldwide interest in view of fast depletion of our oil reserves and food shortages (Kuhad et al., 1997; Gong et al., 1999). Cellulose serves as a vast reservoir of glucose residues linked by β-1, 4 glycosidic bonds. The conversion of cellulosic mass to fermentable sugars by saccharification through biocatalyst cellulase derived from cellulolytic organisms has been suggested as a feasible process and offers potential to reduce use of fossil fuels and reduce environmental pollution (Dale, 1999; Lynd et al., 1999). In addition to this process, the cellulolytic enzymes have also been exploited for commercial applications like malting, wood processing, preparation of denim fabrics in textile industries, maceration of protoplasts from plant tissues and de-inking process in recycling of printed papers. But the saccharification process has not reached to the level of commercialization in certain applications pertaining to production of biofuels. The major obstacle to the exploitation of cellulase is its high cost of production and include other factors like complexity of cellulose structure, the type and source of cellulose employed for production and low amounts of cellulases production by cellulolytic organisms due to catabolite repression influence economics of cellulase production. One effective approach to reduce the cost of enzyme production is to replace pure cellulose by relatively cheaper substrates such as lignocelluloses materials. The development of biorefineries to produce fuels and commodity chemicals from lignocellulosic biomass is viewed as a potential alternative to current reliance on nonrenewable resources. The so-called ‘‘sugar platform,’‘ involving enzymatic hydrolysis of the cellulose component to glucose, followed by fermentation to fuel-grade ethanol, is a focus of current attention. One of the primary challenges for process commercialization is the development of cost-effective pretreatment technologies for lignocellulosic feedstock’s (Lynd et al., 2002; Mosier et al., 2005; Wyman et al., 2005). Pretreatment is necessary to increase the accessibility of cellulose in lignocellulosic biomass to facilitate enzymatic hydrolysis. Unlike traditional sources of fermentable sugar, such as starch and sucrose, the cellulose component of lignocellulose is a structural polymer and is protected against enzymatic attack by the surrounding matrix of lignin and hemi cellulose. In view of biotechnological importance of cellulase, this study was focused on the production of cellulase on natural and pretreated cheap locally available lignocelluloses in submerged fermentation in a laboratory scale by the local isolate of Aspergillus niger isolated from cotton ginning mill effluents. Materials And Methods MicroorganismA local isolate of Aspergillus niger used in the st