Characterization of a thermo-alkali-stable laccase from Bacillus subtilis cjp3 and its application in dyes decolorization

ABSTRACT

In this work, a novel bacterial strain exhibiting laccase activity was isolated from black liquor and identified as Bacillus subtilis cjp3. The CotA-laccase gene was cloned from strain cjp3 and expressed in Escherichia coli. The purified recombinant laccase has a maximum activity of 7320 U/L, maintaining high stabilities under a wide pH range and high temperature conditions. Nearly no loss of laccase activity was observed even at pH 9.0 after 10 h of incubation. Reactive blue 19, reactive black 5 and indigo carmine could be efficiently decolorized by the purified laccase in the presence of a mediator ABTS. More than 86% of tested dyes were removed in 4 h at pH = 9.0. The recombinant laccase can work well in a broad range of temperatures of 20–80°C(>80% relative activity). These special properties indicated the potential use of the CotA-laccase in treating wastewater containing synthetic dyes.

KEYWORDS:

• Bacillus subtilis
• cotA-laccase
• decolorization
• prokaryotic expression

Funding

This work was supported by the National Natural Science Foundation of China (No.51308300) and the Key Research Program of the Chinese Academy of Sciences (Grant No. KZZD-EW-TZ-13), and partially supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD).