Cloning and characterization of CotA laccase from Bacillus subtilis WD23 decoloring dyes

Abstract

CotA protein is a component of the endospore coat of Bacillus subtilis and it exhibits the activities of laccase. CotA protein is known as CotA laccase. A CotA laccase gene from B. subtilis WD23 was cloned and expressed in Escherichia coli. The expressed CotA laccase was observed in an active form. The molecular weight of CotA laccase was estimated to be 67.5 kDa. Optimal laccase activity was detected at pH 7.2 and 45 °C with syringaldazine as substrate. The half-life of the laccase was 1.5 h at 80 °C at the optimum pH. Half of the laccase activity was lost after 8 h at 45 °C and pH 9.0. The CotA laccase exhibited high tolerance to acetone, petroleum ether, ethyl acetate and chloroform, like spore laccase. Purified CotA laccase was activated 157 % by Cu2+ and remained stable to Fe2+. The purified CotA laccase could decolorize 87 % of Remazol Brilliant Blue R (RBBR) and 81 % of Congo Red in 6 h in absence of any mediator.