由微生物介导的吡啶降解技术是解决高盐吡啶环境污染的经济有效方法之一,开发具有吡啶降解性能且能够耐受高盐分的微生物是该类研究的重要前提。本研究从山西太原钢铁公司焦化废水处理厂活性污泥中分离培养了一株耐盐吡啶降解菌,通过菌落形态和16S rDNA基因系统发育分析,鉴定其为红球菌属(Rhodococcus sp.)的细菌。耐盐性实验结果表明,菌株LV4能够在0%-6%盐度范围内生长,并完全降解初始浓度为500 mg/L的吡啶;但当盐度高于4%时,菌株LV4因其生长变缓而导致吡啶完全降解时间明显延长。扫描电镜结果显示,高盐环境会使菌株LV4的菌体细胞分裂变慢,诱导细胞表面分泌更多的颗粒状胞外聚合物(extracellular polymeric substance, EPS)。当盐度不高于4%时菌株LV4主要依靠EPS中蛋白含量的增加来响应高盐环境的冲击。单因素实验优化发现,菌株LV4在盐度为4%的高盐环境中降解吡啶的最佳条件为温度30 ºC、pH 7.0、转速为120 r/min (DO 10.30 mg/L)。最优条件下菌株LV4对于初始浓度为500 mg/L的吡啶,在经过12 h的适应期后,能以(29.10±0.18) mg/(L·h)的最大速率将吡啶完全降解,总有机碳(total organic carbon, TOC)去除率最高可达88.36%,表明菌株LV4对吡啶的矿化效果较好。利用液质联用仪检测到11种吡啶代谢中间产物,推测菌株LV4主要通过环羟基化和环加氢还原2种代谢路径将吡啶完全降解。菌株LV4在高盐环境对吡啶的快速降解,意味着其在高盐吡啶环境污染治理上具有实际应用的潜力。
Biodegradation of pyridine pollutant by microorganisms is one of the economical and effective methods to solve the environmental pollution of pyridine under high salinity conditions. To this end, screening of microorganisms with pyridine degradation capability and high salinity tolerance is an important prerequisite. In this paper, a salt-resistant pyridine degradation bacterium was isolated from the activated sludge of Shanxi coking wastewater treatment plant, and identified as a bacterium belonging to Rhodococcus on the basis of colony morphology and 16S rDNA gene phylogenetic analysis. Salt tolerance experiment showed that strain LV4 could grow and degrade pyridine with the initial concentration of 500 mg/L completely in 0%-6% saline environment. However, when the salinity was higher than 4%, strain LV4 grew slowly and the degradation time of pyridine by strain LV4 was significantly prolonged. Scanning electron microscopy showed that the cell division of strain LV4 became slower, and more granular extracellular polymeric substance (EPS) was induced to secrete in high salinity environment. When the salinity was not higher than 4%, strain LV4 responded to the high salinity environment mainly through increasing the protein content in EPS. The optimum conditions for pyridine degradation by strain LV4 at 4% salinity were 30 ºC, pH 7.0 and 120 r/min (DO 10.30 mg/L). Under these optimal conditions, strain LV4 could completely degrade pyridine with an initial concentration of 500 mg/L at a maximum rate of (29.10±0.18) mg/(L·h) after 12 h adaptation period, and the total organic carbon (TOC) removal efficiency reached 88.36%, indicating that stain LV4 has a good mineralization effect on pyridine. By analyzing the intermediate products in pyridine degradation process, it was speculated that strain LV4 achieved pyridine ring opening and degradation mainly through two metabolic pathways:pyridine-ring hydroxylation and pyridine-ring hydrogenation. The rapid degradation of pyridine by strain LV4 in high salinity environment indicates its application potential in the pollution control of high salinity pyridine environment.