Optimization of endoglucanase production from Trichoderma harzianum strain HZN11 by central composite design under response surface methodology

The utilization of abundantly available lignocellulosic biomass requires an efficient cellulolytic enzyme system. Evaluation of an efficient microbial system is a crucial part for the development of useful enzyme production in an industrial process. The present study reports the production of cellulolytic enzymes from various lignocellulosic biomasses by Trichoderma harzianum strain HZN11 characterized by 18S rDNA sequencing. The organism revealed a well-balanced cellulolytic complex of enzyme production (endoglucanase 30.32 U g⁻¹, exoglucanase 15.08 U g⁻¹, FPase 5.56 U g⁻¹, cellobiase 17.92 U g⁻¹, β-glucosidase 11.21 U g⁻¹, and xylanase 1740 U g⁻¹) from sweet sorghum bagasse under solid-state fermentation. Statistical optimization by Plackett–Burman design constituting of 12 experimental runs at two levels of seven independent variables revealed the significant effect of four variables, namely, protease peptone, lactose, MgSO₄·7H₂O, and K₂HPO₄ on endoglucanase production at 95% confidence level with R ²=97.68%. Response surface methodology using central composite design was employed with 31 experimental runs at 5 levels with 4 significant independent variables. The responses in the form of contour and 3D plots showed significant interaction effects. Significant interactions existed between the variables at p < 0.05 with R ²=97.3%. The model generated through these designs was validated giving a 2.31-fold increase in endoglucanase production. The isolated T. harzianum strain HZN11 produced an efficient pool of cellulolytic enzymes which is essential for efficient hydrolysis of biomass. The strain HZN11 also possessed a significant capability of cellobiase production which is usually deficient in other strains. Higher yields of endoglucanase could be employed for bioethanol production.