Optimization of nutritional factors and copper on laccase production by Pleurotus florida

Laccases as lignocellulolytic enzymes are commonly produced by submerged fermentation, but for more constructive production, it should be preceded by nutritional factors suitable for the fungi’s growth. In the present study, the overproduction of laccase activity resulting from nutritional factor interactions was studied in Pleurotus florida, a white-rot fungi. Response surface methodology (RSM) based on the Box-Behnken factorial design (BBD) was performed to optimize the interaction of glucose and yeast extract concentrations to maximum enzyme activity with and without copper sulfate as an inducer. The results show a quadratic model with a very low p-value (<0.0001) to explain the changes in laccase production as a function of glucose, yeast extract, and copper sulfate concentrations. Based on the coefficient of determination (R2) and mean absolute error, the RSM model provided a good quality prediction for the laccase production with all independent variables. The findings explain that a 4.4-fold increase in laccase activity occurs in the presence of copper compared to cultures without copper with an optimal concentration of glucose and yeast extract as carbon and nitrogen sources, respectively. Maximum laccase activity (5.28 UmL-1) was obtained using optimized conditions (18.70 gL-1 glucose, 8.22 gL-1 yeast extract, and 0.93 mM copper sulfate). This finding could be used to induce high laccase production on a large scale for biomass changeover systems.