Screening Of Bacterium Possessing High Laccese Activity And Decolorizing Dye By Its Spore Laccase

Enrichment medium added with copper ions was used to screen bacteria with laccase activity from forest soil. Combined morphological, physiological and biochemical characteristics and 16S rDNA sequence analysis, a bacteria highly producing-laccese was identified as Bacillus sp. CLb. The spore laccase activity reached the highest value at 46.1 U/mg after 5 days’cultivation. The optimum growth temperature of strain CLb was 37℃ and the optimum growth pH was 7.0. The strain CLb could grow in culture medium containing 1 mol/L Cu2+. The spore laccase of strain CLb could oxidize 2,2’-azino-bis(3-ethylbenzthiazoline-6-sulfonate) (ABTS) and syringaldazine with optimum pH of 3.0 and 7.0, respectively. The optimum reaction temperature for the spore laccase was 70℃ with SGZ as substrate. The spore laccase maitained high activity after incubated at 70℃ for 10 h or pH 9.0 for 10 d. The metalions Na+,Cu2+,Mg2+,Ba+and Co2+ could activate laccase activity, while other metalions such as Mn2+,Hg2+,Ag+ and Al3+ demonstrated a inhibition effect. The spore laccase of strain CLb could decolorize 93%,93%,79% and 92.5% of reactive black 5 in 4 hour, indigo carmine in 2 hour, reactive blue 19 and crystal violet in 6 huor when acetosyringone(ACE) was added to the decolorizing system, RBBR and crystal violet were decolorized by spore laccase from Bacillus sp. CLb in the absence of mediator. The four dyes were decolorized more than 70% by the spore laccase in the presence of ACE. In the present of ACE as mediator and pH7.0, the synthetic dyes were decolorized more efficiently than under pH9.0 condition by spore laccase. The spore laccase-mediator system showed the highest decolorization ability towards the simulated dye effluent with 3 mg/mL of spore laccase and 0.5 mmol/L of ACE at pH9.0. More than 80% of simulated dye effluent was decolorized after 6 h.