Purification and characterization of an extracellular laccase from a Pseudomonas sp. LBC1 and its application for the removal of bisphenol A

The Pseudomonas sp. LBC1 produced extracellular laccase when grown in the nutrient broth. The enzyme was purified using acetone precipitation and an anion-exchange chromatography. The molecular weight of the purified laccase was estimated as 70 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis. An enzyme showed maximum substrate specificity towards o-tolidine than other substrates of laccase including 2,2′-azinobis, 3-ethylbenzothiazoline-6-sulfonic acid, hydroquinone, N,N′-dimethyl phenylene diamine, syringic acid and veratryl alcohol. The optimum pH and temperature for the laccase activity were 4.0 and 40 °C, respectively. Cyclic voltammogram revealed the redox potential of purified enzyme as 0.30 V. The laccase was stable up to 40 °C and within pH range 6.0–8.0. Sodium azide and EDTA strongly inhibited laccase activity. The purified laccase completely degraded the higher concentration of bisphenol A within 5 h. Biodegradation metabolites of bisphenol A were characterized by using FTIR, HPLC and GC–MS.