Effect of solid state fermentation medium optimization on Pleurotus ostreatus laccase production

Abstract

The objective of this work was to increase laccase production by Pleurotus ostreatus PLAB through culture medium optimization using solid state culture conditions. Increased laccase activity was obtained through design of experiments (DOE) using the Taguchi orthogonal array (OA). Seven factors, viz. lignocellulose, glucose, yeast extract, peptone, KH₂PO₄, MgSO₄ 7H₂O and MnSO₄ H₂O at three levels and pH at two levels. OA layout of L18 (2¹ x 3⁷) was selected for the proposed experimental design using Minitab 17 software. Data analysis showed that lignocellulose (20 %) and glucose (10 g L¹) had positive effect, whereas KH₂PO₄, MgSO₄∙7H₂O and MnSO₄∙H₂O did not have significant effect on laccase production. Taguchi OA analysis showed that pH 6, lignocellulose 20 %, glucose 10 g L^-1, yeast extract 6 g L^-1, peptone 15 g L^-1, KH₂PO₄ 3 g L¹, MgSO₄∙7H₂O 0.5 g L^-1 and MnSO₄∙H₂O 0.1 g L^-1 were the optimal conditions to maximize laccase production. The model predicted a 30.37 U g^-1 dry wt., which agreed with the experimentally obtained laccase activity 29.15 U g^-1 dry wt. at optimal conditions.