Cellulase Producing Potential of Aspergillus terreus Uv2 on Cellulosic Wastes Pretreated with Acid and Alkali

Abstract

Aims: Cellulases offer very wide applications in biotechnology and enzymes from microbial origins present inexpensive source. Production of value added chemicals from wastes will be an exciting translation from waste to wealth and an eco-friendly initiative instead of the incineration option often given to cellulosic wastes. Study Design: Sulphuric acid and Sodium hydroxide solutions were prepared at 0.5 M and 2 M concentrations to pretreat three cellulosic wastes that had been made neutral prior to fermentation with a known cellulase producing mold Place and Duration of Study: All experiments were conducted in the laboratory of the Department of Microbiology, Federal University of Technology, Minna, Nigeria for a period of six weeks. Methodology: Hypercellulase producing Aspergillus terreus UV2 strain was used to ferment pretreated cellulosic wastes: Corn cob, corn straw and bagasse, using submerged fermentation in Mandel basal medium. The crystalline lignocelluloses were milled and fractionated into 850 μ particle size and pretreated in two concentrations (0.5 M and 2 M) of both acid (sulphuric acid) and alkali (sodium hydroxide) independently and were left for varying residence time of one hour or three hours in the digester at ambient temperature, Optimum spore concentration of 1.0 x 106 spores/ml and pH of 4.8. Supernatants of crude enzyme were taken and assayed at 24 hours interval. Results: Cellulase activity peaked at 96 hours. Enzyme secretion in the cellulosic wastes was highest in sugarcane bagasse, followed by the corn cob and then the corn straw corresponding to 51%, 40% and 16% respectively. Alkali pretreated cellulosics gave higher yield of cellulase than its counterpart acid. Non-pretreated residues gave only low enzyme titers. Bagasse produced optimum cellulase yield of 0.068 IU/ml/min within 120 hours when subjected to 2 M NaOH digestion for one hour before fermentation. This translated to 39% increase in enzyme expression when compared with non-treated bagasse of 0.049 IU/ml/min. Conclusion: Sugarcane bagasse therefore when digested with mild alkali (2 M NaOH) for a pretreatment period of one hour holds a great possibility for cellulase production using a mutant mold, Aspergillus terreus UV2. Production of value added chemicals from cellulosic wastes will be an exciting translation from waste to wealth.