Evaluation of optimum conditions for improved cell growth and MNP enzyme activity in some selected edible mushrooms

This study was carried out to investigate and optimize conditions for enhanced cell growth and manganese peroxidase (MnP) enzyme activity in selected mushroom isolates. Single parameter optimization of different process variables was carried out for cell growth/enzyme production. The isolates used were Pleurotus porrigens, Gerronema chrysophyllum and Lepiota procera. The influence of temperature, pH, nitrogen sources, and metal ions were examined to determine their effects on both cell proliferation and MnP production of the isolates. Results showed that the optimum growth temperature for MnP enzyme activity for P. porrigens was 35oC. It was also revealed that all the isolates showed optimum growth rate at pH 5. P. porrigens showed the highest growth rate (OD 15.2). Peptone was the best nitrogen source, with P. porrigens having the highest growth rate (OD 0.184). Both Mn2+ and Cu2+ stimulated growth rate in all the isolates, with Mn 2+ (2Mm) stimulating the highest growth rate (OD 22.8) in P. porrigens. Hg2+, Fe3+, Zn2+ and Pb2+ were inhibitory to growth rate. All the isolates showed that the optimization of culture conditions enhanced growth rate of the isolates.