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. 2010 Mar;108(3):998-1006.
doi: 10.1111/j.1365-2672.2009.04505.x. Epub 2009 Jul 30.

Random mutants of a Pleurotus ostreatus laccase as new biocatalysts for industrial effluents bioremediation

A Miele  1   2 , P Giardina  1 , G Sannia  1 , V Faraco  1   2
Affiliations

Random mutants of a Pleurotus ostreatus laccase as new biocatalysts for industrial effluents bioremediation

A Miele et al. J Appl Microbiol. 2010 Mar.

Abstract

Aims: To select better performing laccase variants among the 2300 randomly mutated variants of Pleurotus ostreatus POXA1b laccase to develop improved laccase-based biocatalysts.

Methods and results: Screening of collections of 2300 randomly mutated variants of POXA1b was performed by assaying activity towards the phenolic substrate 2,6-dimethoxyphenol. Two new variants endowed with higher enzyme activity than the wild-type laccase were characterized, and their ability to decolourize industrial dyes with complex trisazo-, polyazo- and stilbene-type structures, in the absence of mediators, was demonstrated. One of the mutants (2L4A) was also proved to be highly stable at both acidic and alkaline pH values (displaying a half-life of around 1 month at the pH levels of both 5 and 10).

Conclusions: In comparison with the wild-type laccase, the new selected 2L4A mutant shows a significant increase in stability at acidic pH, whilst storing its high stability at alkaline pH. This variant also represents a more versatile enzyme with respect to both the variety of xenobiotics degraded and the operative conditions.

Significance and impact of the study: This work represents the first example of improvement of a basidiomycete laccase for industrial effluents bioremediation by directed evolution.

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