Biochemical characterization of three phase partitioned laccase and its application in decolorization and degradation of synthetic dyes

Growing laccase utilization in numerous biotechnological applications encourages the search for high benefit/cost ratio purification methods such as Three Phase Partitioning (TPP). TPP was employed to the crude extract of Pleurotus ostreatus, gave yielded nearly 161% with 27.8 fold purity. The specific activity of the TPP purified laccase was 91 U/mg and the molecular mass of isozymes was estimated to be 72 kDa and 40 kDa. An extracellular laccase acted optimally at pH 6.0 and exhibited an optimum temperature of 45 °C. The enzyme was able to sustain its activity even at elevated temperatures (50–60 °C) for extended periods (2–3 h). Laccase displayed a high affinity towards syringaldazine and oxidizes other phenolic compounds. This laccase was activated by Mn2+ and glycerol, but completely inhibited by the classic laccase inhibitors, oxalic acid, Hg2+, Pb2+ and Fe2+. The purified laccase could efficiently decolorize triphenyl methane (TPM), azo and indigo dyes without addition of redox mediators. The biodegradation of malachite green (MG) was monitored by UV–vis, IR-spectroscopy and HPLC. The thermostable and rapid dye decolorizing property makes it an attractive and promising biocatalysts for the environment biotechnological applications.

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► We have developed simple, rapid and scalable purification procedure like Three Phase Partitioning to purify laccase from the crude extract of Pleurotus ostreatus, has helped us obtain 161% yield with 27.8 fold purity.
► High substrate affinity, broader pH and substrate range of the thermostable laccase indicates that it is highly favorable biocatalysts for industrial applications.
► Laccase was found to be capable of decolorizing different groups of dyes without mediators.
► Biotransformation of ‘malachite green’ was studied using UV spectroscopy, HPLC and FTIR.