Production of laccase from newly isolated Pseudomonas putida and its application in bioremediation of synthetic dyes and industrial effluents

A novel laccase enzyme producing bacterium, Pseudomonas putida MTCC 7525, was isolated and subjected to optimization of laccase production. Maximum production (94.10 U/ml) was achieved at 30 °C and pH 8 (108 h incubation) with 10% skim milk and 1 mM sodium nitrate as additional nitrogen source. The laccase was purified by salt precipitation followed by ion exchange chromatography which showed 6.44 fold purification. The purified enzyme had optimal activity at pH 8.0 and 40 °C, and showed stability in DMSO retaining more than 85% of original activity. In presence of manganese and cadmium, enzyme retained >95% and 92% activity, respectively. The molecular weight of laccases was 39.5 kDa and activity was inhibited by pCMB (93%). The synthetic dyes (0.02%) and industrial effluents (10%) were decolorized to 74–93 and 58–68%, respectively when treated with culture of P. putida. However, the culture supernatant of P. putida showed about 36–94 and 16–86% decolorization of synthetic dyes and effluents, respectively within 24 h of incubation.