Copper improves the production of laccase by pleurotus sajor-caju with ability to grow on effluents of the citrus industry

Abstract

This research is aimed to evaluate the effect of copper on biomass growth, laccase activity and isoenzymes composition of Pleurotus sajor-caju, and its ability to grow on effluents of the citrus industry. The inhibitory effect of copper on growth was evidenced especially after 14 days of culture in the presence of the highest concentration of copper (1 mM) reducing almost three times its growth. The highest enzyme activity was reached at the 10th day of treatment, with ~ 53 U/L for the medium without copper and ~ 121 and ~ 68 U/L for medium supplemented with 0.5 and 1mM, respectively. Laccases in cell-free extracts obtained from culture added with copper showed to be more stable for more time at temperature changes. The optimum temperature for laccase activity increased from 50 to 60°C by effect of copper while the optimal pH was 5 in all experiments. In gels, it was possible to observe two isoenzymes of 65 and 35 kDa whose expression varied according to incubation time. Moreover, the isoenzyme of low molecular weight was induced by the presence of effluent in solid medium. P. sajor-caju had the ability to grow on effluents from the citrus industry, showing tolerance and potential for waste treatment, constituting a possible alternative to biodegrade and reduce the contaminating impact of effluents.