Molecular cloning, characterization, and dye-decolorizing ability of a temperature- and pH-stable laccase from Bacillus subtilis X1.
Laccases from fungal origin are typically unstable at high temperatures and alkaline conditions. This characteristic limits their practical applications. In this study, a new bacterial strain exhibiting laccase activity was isolated from raw fennel honey samples and identified as Bacillus subtilis X1. The CotA-laccase gene was cloned from strain X1 and efficiently expressed in Escherichia coli in a biologically active form. The purified recombinant laccase demonstrated an extensive pH range for catalyzing substrates and high stability toward alkaline pH and high temperatures. No loss of laccase activity was observed at pH 9.0 after 10 days of incubation, and approximately 21 % of the initial activity was detected after 10 h at 80 °C. Two anthraquinonic dyes (reactive blue 4 and reactive yellow brown) and two azo dyes (reactive red 11 and reactive brilliant orange) could be partially decolorized by purified laccase in the absence of a mediator. The decolorization process was efficiently promoted when methylsyringate was present, with more than 90 % of color removal occurring in 3 h at pH 7.0 or 9.0. These unusual properties indicated a high potential of the novel CotA-laccase for industrial applications.
Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, Wuxi, 214122, People's Republic of China, guanzb@jiangnan.edu.cn.
Zheng-Bing
ZB
Guan
Ning
N
Zhang
Chen-Meng
CM
Song
Wen
W
Zhou
Lin-Xi
LX
Zhou
Hong
H
Zhao
Cheng-Wen
CW
Xu
Yu-Jie
YJ
Cai
Xiang-Ru
XR
Liao
D001391:Azo Compounds / Q000737:chemistry; D001412:Bacillus subtilis / Q000201:enzymology*; D001673:Biodegradation, Environmental; D003001:Cloning, Molecular; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D042845:Laccase / Q000737:chemistry / Q000235:genetics*; D055550:Protein Stability
D001391:Azo Compounds; C578910:reactive brilliant orange; D042845:Laccase