Factorial design for optimization of laccase production from Pleurotus ostreatus IMI 395545 and laccase mediated synthetic dye decolorization

In the present study, Plackett–Burman design (PBD) followed by response surface methodology (RSM) was used to optimize the culture medium composition for laccase production from Pleurotus ostreatus IMI 395545. Influence of carbon, nitrogen (sources) and inducer were evaluated by Plackett–Burman design. The factors that induce positive effect on enzyme production were further optimized using central composite design of RSM. The multiple regression equation was used to optimize the values of carbon, nitrogen and inducer for maximum enzyme production. The optimized values were found to be 1.8 g L, 0.76 g L and 164.95 μM for glucose, ammonium nitrate and copper sulphate, respectively. The maximum enzyme activity of 2.7 U mL obtained experimentally was very close to the predicted response, 2.5 U mL. Furthermore, optimized laccase was used for decolorization of synthetic dyes, such as, reactive blue 172 and reactive red 22, which are routinely used in textile industries. Fourier transform infrared spectroscopy was performed to confirm the decolorization of the studied dyes by laccase. Allium cepa toxicity test was performed, which indicated that root growth inhibition was dependent upon the concentration of dye.