间甲酚降解菌Citrobacter farmeri的降解特性及代谢途径解析

DEGRADATION CHARACTERISTICS OF m-CRESOL BY CITROBACTER FARMERI AND THE ELEMENTARY STUDY OF METABOLIC PATHWAY

考察了在不同温度、pH值、摇床转速、氮源等环境和营养条件下,间甲酚降解菌Citrobacter farmeri对降解速率和降解过程中反应液的TOC值、紫外吸收及酶活的变化.结果表明,Citrobacter,farmeri降解间甲酚的最适温度为35℃,培养基初始pH值为6.5-8.0,摇床转速为170 r·min^(-1),无机氮比有机氮和氨态氮比硝态氮更利于Citrobacter farmeri对间甲酚的降解;当间甲酚初始浓度低于375mg·l^(-1)时,Citrobacter farmeri降解间甲酚符合零级动力学方程;间甲酚初始浓度约为60 mg·l^(-1)时约4 h完全降解,TOG的去除率8 h内可达到77%,之后几乎不变;Citrobacter farmeri可完全降解约600 mg·l^(-1)的间甲酚,表现出高效与强耐受能力的结合.对酶活的测定发现,儿茶酚1,2-双加氧酶有明显增大,初步判断Citrobacter farmeri以邻位裂解的途径对间甲酚进行降解.

A m-cresol degrading bacterium named Citrobacter farmeri, which utilizes m-cresol as sole source of carbon and energy, was isolated from an aerobic activated sludge in a coke-plant wastewater biological treatment system. Some environmental and nutrition conditions for the biodegradation of m-cresol by Citrobacter farmeri such as temperatures, initial pH, shaker rotary speeds and nitrogen sources were studied. TOC, UV scans and key enzyme activities related to the ring-cleaving were measured to analyze the metabolic pathway. The optimal conditions are found to be temperature at 35 ℃, pH 6. 5-8.0, and 170 r·min^-1 shaker rotary speed respectively. The effects of different nitrogen sources on biodegradation were investigated and the order was NH4Cl≈ （NH4）2SO4 〉 NH4NO3 〉 CO（NH2）2 which shows the inorganic nitrogen is easier to be utilized. The degradation reaction of m-cresol by Citrobacter farmeri can be described with zero order kinetic equation when the initial m-cresol concentration islower than 375 mg·l^-1. m-Cresol was degraded completely in 4 hours when the initial concentration was 60 mg·l^-1, and TOC removal efficiency was 77% in 8 hours and then nearly kept constant. Catechol 1,2-dioxygenase had obvious augmentation when detected the enzyme activity which means Citrobacterfarmeri degrades m-cresol through orth-cleaving pathway.