Transformation of herbicide 2,4-D butyl ester by laccase from a new Ganoderma strain

The laccase produced by Ganoderma sp.ST,a strain newly selected by our group,was capable of transforming a phenoxy-hydroxy-acid herbicide 2,4-D butyl ester in the absence of redox mediators.The laccase-substrate system was optimized with pH,enzyme concentration and temperature.The laccase used efficiently transform 2,4-D butyl ester with 0.5 mg/L at a pH range from 4.0 to 8.0 and temperature range from 15℃ to 30℃.Under the optimal conditions(pH7.0,25 U/L laccase and 30℃),the transformation rate was positively correlated to reaction time and reached above 99.5% after approximately 24 h.Laccase activity was stable during the test time.In addition,the transformation rate obtained in tap water was nearly identical to that obtained in citrate-Na2HPO4 buffer.