假单胞菌N7的萘降解特性及其降解途径研究

应用HPLC和UV分析技术,以萘为代表性多环芳烃污染物,研究了假单胞菌N7对水中萘的降解特性.结果表明,营养盐、微量元素的添加可使萘的降解率提高23.65%;溶解氧高于4.3 mg/L时萘降解率达95.66%并趋于稳定;随萘浓度增加降解率逐渐下降;在中性和弱碱性环境下,降解效果较好,萘降解率均在82.88%以上.在30℃、转速为165 r/min的摇床中处理pH7.5、萘浓度为100 mg/L的水样72 h,其最大降解率为95.66%.通过检测菌株N7处理含不同底物水样时其吸光度、pH和底物的变化情况,证实菌株N7亦能降解甲苯、二甲苯、苯酚、2,4-二硝基苯酚、苯甲酸、1-萘酚和水杨酸,并以其为唯一的碳源和能源生长繁殖,表明该菌株能适应环境中芳烃类物质种类的变化,具有很好的降解多样性.经UV-Vis和GC-MS分析各降解阶段的中间产物,初步确定了该菌对萘的降解途径:一条是邻苯二甲酸途径;另一条是水杨酸途径,萘先被氧化为1,2-二羟基萘,再开环生成水杨酸、邻苯二酚和2-羟基粘康酸半醛,最终进入三羧酸循环(TCA).

Characteristics and Pathway of Naphthalene Degradation by Pseudomonas sp. N7

The biodegradation characteristics of a typical polycyclic aromatic hydrocarbon, naphthalene by the strain (Pseudomonas sp. N7) were investigated by using HPLC and UV analytical techniques. The results showed that the addition of nutritious salt and microelements accelerated the degradation of naphthalene by 23.65%. Degradation efficiency increased with increasing dissolved oxygen and reached 95.66%, then remained stabilized when dissolved oxygen was over 4.3 mg/L, yet decreased with increasing naphthalene concentration. Neutral and weak alkaline condition favored the biodegradation with degradation capacity all over 82.88%. Pseudomonas sp. N7 had a maximum degradation capability of 95.66% when dealing with 100 mg/L naphthalene at 30 degrees C and pH 7.5 with 165 r/min rotary shaking for 72 h. By measuring the absorbance, pH and degradation of substrates during treatment of different substrate with strain N7, it was demonstrated that Pseudomonas sp. N7 could also degrade other aromatic hydrocarbons, such as toluene, dimethylbenzene, phenol, 2,4-nitrophenols, benzyl acid, 1-naphthol and salicylic acid, utilizing each of them as sole carbon and energy source for growth and breeding, thus showing its good biodegradation diversity. The pathway of naphthalene degradation was explored through analyzing metabolic intermediates at different degradation stages by using UV-Vis and GC-MS. The result revealed that there were two possible degradation pathways for naphthalene: one was phthalic acid pathway, and the other was that naphthalene was first oxidized to 1,2-dihydroxynaphthalene, and then the cleavage of rings caused the formation of salicylic acid, catechol, and 2-hydroxymuconic semial-dehyde. Finally these metabolites entered the tricarboxylic acid cycle (TCA).