Optimization of laccase and manganese peroxidase production in submerged culture of Pleurotus sajorcaju
A white-rot fungus, Pleurotus sajor-caju, was isolated from coastal Tanzania and screened for crude lignolytic enzymes production using rhemazol brilliant blue R (RBBR) dye, 2,2-azino-bis (3- ethylbenzthiazoline)-6-sulfonate (ABTS) and guaiacol in a semi-solid medium. Laccase (Lac) and manganese peroxidase (MnP) were detected by a-napthol and pyrogallol solutions, respectively, on the guaiacol supplemented semi-solid media. The effect of temperature, pH, carbon, nitrogen, Cu2+, 2,5- xylidine, ferulic acid, Mn2+ and immobilization using Luffa cylindrica sponges in submerged culture fermentations were investigated for maximum enzymes production. After 7 days of incubation, 83 to 100% oxidation of RBBR, ABTS and guaiacol was observed. With optimized culture conditions, the fungal filtrate had maximum Lac and MnP activities of 80 and 0.94 U/ml, respectively compared to 0.62 and 0.0003 U/ml obtained with non-optimized ones; amounting to 129 and 3133 times increase in Lac and MnP activities, respectively. The improved crude enzymes activities, RBBR decolourization, ABTS and guaiacol oxidation capabilities of P. sajor-caju show its potential as a source of industrial enzymes for biotechnological applications.
Key words: White-rot fungi, optimization, Pleurotus sajor-caju, laccase, manganese peroxidase, submerged fermentation, immobilization.