一株木材腐朽菌及其粗酶液对七氯的降解

Phlebia acanthocystis TMIC34875是一株具有七氯降解能力的木材腐朽菌。为利用微生物技术去除环境中的七氯残留提供理论依据,研究了该菌株及其粗酶液对七氯的降解性能及其动力学特性。结果表明,菌株在七氯的初始浓度为50μmol/L时具有最大降解速率,为0.3031μmol/（L·h）;而菌体接种量为15%时,降解速率达到最高,为0.2045μmol/（L·h）。降解酶定位研究表明,七氯的降解主要是胞内酶在起作用。七氯胞内酶降解的酶促反应最适温度是35℃,在30-40℃之间有较高的催化活性;最适pH值为5.0,在pH 4.5-6.0之间有较高的催化活性,最适条件下反应1 h后七氯的降解率为65%。胞内粗酶液降解七氯的米氏常数K m为5.42μmol/L,最大反应速率V max为4.55μmol/min。胞内酶处理体系的GC/MS图谱显示,主要降解产物为1-羟基六氯、1-羟基-2,3-环氧六氯和环氧七氯,表明胞内酶对七氯的初始代谢机理同菌株相似,均是通过环氧化和置换反应来完成的。

Degradation of heptachlor by a wood-rot fungus and its enzyme

A wood-rot fungus Phlebia acanthocystis TMIC34875 capable of degrading organochlorine insecti-cide heptachlor was previously isolated. In order to provide theoretical evidence for the application of this fungus in the bioremediation of residual heptachlor in the environment, the kinetic properties of biodegradation of hepta-chlor by P. acanthocystis TMIC34875 and its crude enzyme were studied. This strain showed eompatatively grea-test degradation rate with an initial heptachlor concentration of 50 μmol/L. The appropriate incubation density for enzymatic degradation was 15% （1.5 ×10^6 CFUs/mL）. The results showed that heptaehlor degrading en-zyme was intracellular enzyme. The optimum pH was 5.0 for enzymatic degradation of heptaehlor, and it had high activity in the range of pH 4.5 - 6.0. The optimum temperature for enzymatic degradation of heptachlor was 35℃ , it still had high activity in the range of 30 -40℃. The crude enzyme showed Michaelis-Mentn＇ s constant （Km ） for heptachlor of 5.42 μmol/L, and the maximal degradation rate （ Vmax ） was 4. 55 μmol/min. The re-suits of GC/MS analysis revealed that heptachlor was degraded by intracellular enzyme to heptachlor epoxide, 1-hydroxychlordene, and 1-hydroxy-2,3-epoxychlordene through epoxidation or substitution of chlorine atom by hy-droxyl group.