Production of cellulase by Pleurotus ostreatus and Pleurotus sajor-caju in solid state fermentation of lignocellulosic biomass

Bioconversion of cellulosic components into fermentable sugars has currently been accomplished with the help of the microbial enzyme, cellulase. In this study, Pleurotus ostreatus (Jacquin ex Fr.) Kummer and Pleurotus sajor-caju (Fr.) Singer were tested for cellulase production by solid state fermentation (SSF) using saw dust, sugarcane bagasse, and paddy straw as substrate. To enhance production, the substrates were pretreated with 1% and 4% NaOH solutions. Supernatants of extracted enzyme solutions were used to estimate reducing sugar and soluble protein, as well as enzyme activities. Maximum production of reducing sugar and soluble protein were recorded in 12 and 10 day fermented products, respectively. In the production of reducing sugars, P. ostreatus (42.8 mg g^-1) was found to be more efficient than P. sajor-caju (10.9 mg g^-1), while P. sajor-caju was more efficient in soluble protein production (40.2 mg g^-1) compared to P. ostreatus (3.1 mg g^-1). P. ostreatus was found to be more efficient in the individual components of cellulase enzyme production than P. sajor-caju. All the enzyme activities were found to attain a peak at 10 days of fermentation. The highest activities of endoglucanase, exoglucanase, and β-glucosidase were recorded as 7.08, 7.36, and 3.60 units (μmole of glucose released/min/g substrate), respectively, for P. ostreatus, while that of P. sajor-caju were 1.9, 2.03, and 2.63 units, respectively. Total cellulase activity was found to reach a maximum at 10 days of fermentation for both strains. For P. ostreatus it was recorded as 3.51 units, while for P. sajor-caju it was 0.82 units. This study suggests P. ostreatus as an important source of cellulase enzymes.