Optimization of laccase production using response surface methodology coupled with differential evolution

In the present study, laccase production from a locally isolated hyperactive strain of Pleurotus sp. under solid state fermentation (SSF) was carried out and the interactions between different parameters of fermentation were studied using response surface methodology. The saddle shaped response surface plots depicting dual conditions for the enhanced production indicated the presence of isozymes with production optima at different conditions which was verified experimentally. Isoelectric focusing of the enzyme extract revealed that two isoforms were found with a widely varying pI of 3.8 and 9.3 emphasizing the capacity of the enzyme to be deployed at both acidic and alkaline conditions. Optimization of production conditions by coupling the regression equation with differential evolution technique yielded over 54,600 IU/gds (3,412,500 U/L) with a surfactant concentration of 0.016%, pH 7.99, particle size of 0.25 cm, liquid to solid ratio of 4.99 and an incubation period of 8 days. In this study, the optimization process yielded highest titer value of laccase reported to date.