Efficient secretory production of CotA-laccase and its application in the decolorization and detoxification of industrial textile wastewater

Abstract

Fungal laccases are typically unstable at high pH and temperature conditions, which limit their application in the decolorization of textile wastewater. By contrast, the highly stable bacterial laccases can function within a wider pH range and at high temperatures, thus have significant potential in treatment for textile wastewater. In our previous work, a thermo-alkali-stable CotA-laccase gene was cloned from Bacillus pumilus W3 and overexpressed in Escherichia coli. In this study, the robust CotA-laccase achieved efficient secretory expression in Bacillus subtilis WB600 by screening a suitable signal peptide. A maximum CotA-laccase yield of 373.1 U/mL was obtained at optimum culture conditions in a 3-L fermentor. Furthermore, the decolorization and detoxification of textile industry effluent by the purified recombinant CotA-laccase in the presence and absence of redox mediators were investigated. Among the potential mediators that enhanced effluent decolorization, acetosyringone (ACS) was the most effective. The toxicity of the CotA-laccase-ACS-treated effluent was greatly reduced compared with that of the crude effluent. To the best of our knowledge, this study is the first to report on the heterologous expression of CotA-laccase in B. subtilis. The recombinant strain B. subtilis WB600-5 has a great potential in the industrial production of this bacterial enzyme, and the CotA-laccase-ACS system is a promising candidate for the biological treatment of industrial textile effluents.

Decolorization of recalcitrant dyes by a multicopper oxidase produced by Iodidimonas sp. Q-1 with iodide as a novel inorganic natural redox mediator

“…It is well-known that redox mediators such as ABTS, HOBt, and some lignin-derived compounds sometimes enhance enzyme action dramatically 19 . However, significantly fewer efforts have been made to understand the potential decolorization activity of bacterial laccase-like MCOs, except for a spore coat laccase-like protein (CotA) of Bacillus spp 24 – 27 . In this study, we found that IOX, a novel MCO produced by an iodide-oxidizing bacterium Iodidimonas sp.…”

Applications of Microbial Laccases: Patent Review of the Past Decade (2009–2019)

“…A wide array of compounds has been used in the literature as mediators, such as 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), ABTS ( [14], 1-hydroxybenzotriazole (1-HBT) [38], syringaldehyde, vanillin, α-naphthol [39], and others. The laccase-mediator system (LMS) has been used for the removal of residual lignin in biomass [13,40], or the treatment of recalcitrant pollutants, such as antibiotics [39] or other drugs [41], pesticides [42], industrial textile wastewater [43], and even synthetic fragrances [44]. LMS has been also used for the oxidative synthesis of platform chemicals [45].…”

Enhanced catalytic efficiency of CotA-laccase by DNA shuffling

“…Spore coat protein A (CotA) from Bacillus subtilis, a 65 kDa protein (513 amino acids), is a high thermostable bacterial laccase [4]. The CotAlaccase has been reported for industrial textile wastewater detoxification and decolorization [5,6]. Low production yield of the native CotAlaccase limited the applications in industry.…”