A Statistical Approach for Optimization of Simultaneous Production of -Glucosidase and Endoglucanase by Rhizopus oryzae from Solid-State Fermentation of Water Hyacinth Using Central Composite Design

The production cost of -glucosidase and endoglucanase could be reduced by using water hyacinth, an aquatic weed, as the sole carbon source and using cost-efficient fermentation strategies like solid-state fermentation (SSF).In the present study, the effect of different production conditions on the yield of -glucosidase and endoglucanase by Rhizopus oryzae MTCC 9642 from water hyacinth was investigated systematically using response surface methodology. A Central composite experimental design was applied to optimize the impact of three variables, namely, substrate concentration, pH, and temperature, on enzyme production. The optimal level of each parameter for maximum enzyme production by the fungus was determined. Highest activity of endoglucanase of 495？U/mL was achieved at a substrate concentration of 1.23%, pH 7.29, and temperature 29.93 C whereas maximum β-glucosidase activity of 137.32 U/ml was achieved at a substrate concentration of 1.25%, pH 6.66, and temperature 32.09 C.There was a direct correlation between the levels of enzymatic activities and the substrate concentration of water hyacinth as carbon source. 1. Introduction Cellulose being an abundant and renewable resource is a potential raw material for the microbial production of food, fuel, and chemicals [1]. The bioconversion of cellulosic materials has been receiving attention in recent years. Complete enzymatic hydrolysis of enzymes requires synergistic action of three types of enzymes, namely, cellobiohydrolase, endoglucanase, and β-glucosidase [2]. The high cost of production of these enzymes has hindered the industrial application of cellulose bioconversion [3]. Production cost of cellulases may be brought down by multifaceted approaches which include the use of cheap lignocellulosic substrates for fermentation production of the enzyme, the use of cost-efficient fermentation strategies like solid-state fermentation (SSF) [4] as the use of SSF as a production method of enzymes could offer some apparent economic and engineering advantages over the classical submerged fermentation (SmF) [5, 6], and the optimization of the key factors of the fermentation process. Large quantities of cellulosic wastes are generated everyday through forestry and agricultural processes [7] which remain unutilized and accumulate as wastes in the environment thereby causing pollution problem [8]. Water hyacinth (Eichornia crassipes) is one of the fastest growing aquatic weeds that causes huge economic loss by impeding water flow, accelerating water evaporation, increasing mosquito breeding, and destroying rice