Isolation of laccase-producing strain Bacillus amyloliquefaciens LC03 and characterization of its spore laccase.

To obtain bacterial laccase with excellent properties, enrichment medium supplemented with copper ions was used to screen laccase-producing bacterial strains from forest soil. A bacterial strain LC03 exhibiting high laccase activity was isolated and identified as Bacillus amyloliquefaciens, using physiological and biochemical tests as well as 16S rDNA sequence analysis. Strain LC03 demonstrated the highest spore laccase activity of 48.5 U/ g after 6 days cultivation. Its spore laccase could oxidize 2,2'- azino-bis(3-ethylbenzthiazoline-6-sulfonate) (ABTS) and syringaldazine with optimum pH of 3.8 and 6.8, respectively. Optimal reaction temperature for the spore laccase was 60 益with SGZ as substrate. The spore laccase maintained high activity after incubation at 70 °c for 10 hours or pH 9.0 for 10 days. Meanwhile, it was also resistant to laccase inhibitors such as SDS and EDTA. The metal ions Li+ , Na+ , Mg2 + , Ca2 + , Ba2 + and Al3 + could activate laccase activity, while other metal ions such as Ag+ , Mn2 + , Hg2 + and Co2 + demonstrated an obvious inhibition effect. The results showed that the spore laccase from B. amyloliquefaciens LC03, which possessed good stability at high temperature and alkaline conditions, could be used in many industrial fields, including wastewater treatment.