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Abstract
Laccases (EC 1.10.3.2) are a class of multi-copper oxidases with important industrial values. A basidiomycete strain Cerrena sp. HYB07 with high laccase yield was identified. After cultivation in the shaking flask for 4 days, a maximal activity of 210.8 U mL−1 was attained. A 58.6-kDa laccase (LacA) with 7.2% carbohydrate and a specific activity of 1952.4 U mg−1 was purified. 2,2′-Azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) was the optimal substrate, with K m and k cat being 93.4 µM and 2468.0 s−1, respectively. LacA was stable at 60°C, pH 5.0 and above, and in organic solvents. Metal ions Na+, K+, Ca2+, Mg2+, Mn2+, Zn2+ enhanced LacA activity, while Fe2+ and Li+ inhibited LacA activity. LacA decolorized structurally different dyes and a real textile effluent. Its gene and cDNA sequences were obtained. Putative cis-acting transcriptional response elements were identified in the promoter region. The high production yield and activity, robustness and dye decolorizing capacity make LacA and Cerrena sp. HYB07 potentially useful for industrial and environmental applications such as textile finishing and wastewater treatment.
Highlights
Dyestuffs are lost in industrial effluents, posing health and environmental threats [1,2]
HYB07 [21] was kept in the culture collection of College of Biological Sciences and Technology, Fuzhou University and maintained through periodic transfers on potato dextrose agar (PDA) (Difco, Franklin Lakes, New Jersey, USA) at 4uC
HYB07 was amplified by PCR and sequenced, and HYB07 was classified based on its 18S rDNA sequence
Summary
Dyestuffs are lost in industrial effluents, posing health and environmental threats [1,2]. Laccases may provide a green and efficient alternative for decolorizing dyes before discharge into sewage treatment systems or the environment. Laccases catalyze dye transformation, leading to dye decolorization and often detoxification as well [3,4,5,6,7]. Laccases are copper-containing oxidases catalyzing oxidation of phenolic/non-phenolic lignin-related compounds and recalcitrant environmental pollutants [8]. Artificial or natural redox mediators such as 2,29-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and acetosyringone (ACE) broaden the range of laccase substrates [4]. Because laccases have low substrate specificity, utilize oxygen as final electron acceptor and produce water as only by-product, they find applications in paper pulping and bleaching, textile refining, dye decolorization, bioremediation, organic synthesis, juice and wine clarification, etc. Because laccases have low substrate specificity, utilize oxygen as final electron acceptor and produce water as only by-product, they find applications in paper pulping and bleaching, textile refining, dye decolorization, bioremediation, organic synthesis, juice and wine clarification, etc. [3]
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