微生物-化学水解联合作用下烟嘧磺隆的降解

Degradation of Nicosulfuron by Combination Effects of Microorganisms and Chemical Hydrolysis

从被烟嘧磺隆污染的人工湿地土壤中分离出1株能够在葡萄糖存在下降解烟嘧磺隆的微生物,通过16S rDNA序列同源相似性分析,初步鉴定该微生物为Klebsiella sp..它能够以烟嘧磺隆为唯一氮源生长,其最适生长条件为:温度35℃,初始pH为中性偏酸.水解试验表明,烟嘧磺隆在中性和碱性条件下比较稳定,在酸性条件下水解较快.生物降解试验发现,当培养液中葡萄糖浓度为5 g.L-1时,在温度35℃、初始pH为7的条件下培养10 d后烟嘧磺隆有99.4%得到降解,同时溶液的pH从7.0降低至4.0;而降低葡萄糖浓度分别为500 mg.L-1和100 mg.L-1时,培养10 d后烟嘧磺隆的降解率仅为11.7%和6.6%,溶液的pH始终在7左右.进一步研究表明烟嘧磺隆的降解是由于微生物代谢葡萄糖产生了酸性环境,pH降低引起了烟嘧磺隆水解,菌种对烟嘧磺隆降解的实质是微生物-化学水解联合作用.

A strain which was capable of degrading nicosulfuron in the presence of glucose was isolated from nicosulfuron contaminated wetland soil, and it was identified as Klebsiella sp. based on 16S rDNA gene sequencing analysis. The strain could grow using nicosulfuron as the sole nitrogen source. The optimal temperature was 35℃ and the initial pH was neutral to weak acid. Hydrolysis experiments indicated that nicosulfuron remained stably under neutral and alkaline conditions, while in acidic conditions, it hydrolyzed quickly. Based on biodegradation experiments, when the concentration of glucose in culture was 5 g·L-1, the strain could degrade 99.4% of nicosulfuron after incubation for 10 days at 35℃, initial pH=7; pH of the solution decreased from initial 7.0 to 4.0 in the meantime. When the concentration of glucose in culture solution was decreased to 500 mg·L-1 and 100 mg·L-1, with other conditions unchanged, only 11.7% and 6.6% of nicosulfuron were degraded, respectively, and pH of the solution remained at around 7.0. It was proposed that the degradation of nicosulfuron was caused by hydrolysis under acidic conditions at low pH which was resulted from the biodegradation of glucose by the strain. Therefore, the removal of nicosulfuron was actually caused by combined effects of microorganisms and chemical hydrolysis.