球形红细菌降解2,4-二硝基甲苯的途径及酶学性质

采用气相色谱-质谱联用仪(GC-MS)分析了球形红细菌降解2,4-二硝基甲苯(2,4-DNT)的中间代谢产物,分析了可能的降解途径,讨论了培养基中2,4-DNT的初始质量浓度、溶液pH值及反应温度对3种酶的酶比活力影响。结果表明,当2,4-DNT的初始质量浓度为40 mg/L时,培养72h后,可以检测到5种物质:2,4-二硝基甲苯、4-氨基-2硝基甲苯、2-氨基-4硝基甲苯、4-硝基-1,2-二(三甲基硅烷)苯、1,2,4-三(三甲基硅烷)苯,其可能的降解途径为2,4-DNT首先还原为4-氨基-2-硝基甲苯和2-氨基4-硝基甲苯,再进一步转化为4-硝基-1,2-羟基苯,然后氧化为1,2,4-三羟基苯,之后开环生成β-酮己二酸,最终降解为小分子物质。硝基还原酶、邻苯二酚2,3-双加氧酶和邻苯二酚1,2-双加氧酶的酶比活力最适宜温度分别为35、30、35℃,最适宜pH值分别为7.0、8.0、7.0,最适宜培养基初始2,4-DNT质量浓度均为40mg/L。

Degradation Pathway and Properties of Enzyme of 2,4-Dinitrotoluene by Rhodobacter Sphaeroides

The intermediates of 2,4-dinitrotoluene (2,4-DNT) metabolized by rhodobacter sphaeroides were analyzed by the gas chromatograph-mass spectrometer (GC-MS),the possible degradation pathway was analyzed,and the effect of initial mass concentration of 2,4-DNT in culture medium,pH value of solution and reaction temperature on the enzyme specific activity of three kinds of enzymes was discussed.The results show that five intermediates including 2,4 dinitrotoluene,4-amino-2-nitrotoluene,2-amino-4-nitrotoluene,4-nitro-1,2-di(TMS) benzene and 1,2,4-tri(TMS) benzene were detected when initial mass concentration of 2,4-DNT is 40 mg/L after cultivating for 72h.The possible degradation pathway is that 2,4-DNT is first reduced to 4-amino-2-nitrotoluene and 2-amino-4-nitrotoluene and further transformed into 4-nitro-1,2-hydroquinone,then is oxidized to 1,2,4-trihydroxybenzene,finally 1,2,4-trihydroxybenzene ring is cleaved to form β-ketoadipic acid,which was finally degraded to smaller molecular compounds.For enzyme specific actiyity of nitroreductase,catechol 2,3-dioxygenase and catechol 1,2-dioxygenase,the optimal temperature is 35,30 and 35 ℃,respectively,the optimal pH value is 7.0,8.0 and 7.0,respectively and the optimal initial mass concentration of 2,4-DNT in culture medium is 40mg/L.