【作者】 章剑丽；

【导师】 仵彦卿；

【作者基本信息】 上海交通大学 ， 环境科学， 2010， 硕士

【摘要】 地下水石油烃污染对人类健康和生态环境具有很大危害,苯系化合物(BTEX)是石油烃污染中的重要组成成分之一。苯系物具有“三致效应”,己被世界卫生组织确定为强致癌物质。微生物降解苯系化合物是一种有效的生态处理方法。本实验以上海金山化工区污水处理厂处理废水的活性污泥为菌源,以甲苯、乙苯、邻二甲苯、间二甲苯、对二甲苯作为底物,在好氧条件下,经过驯化和筛选得到能降解苯系物的7种菌(TEX-1~TEX-7)。通过16SrDNA序列测试,确认TEX-1为假单细胞菌属(Pseudomonas sp.),TEX-2节杆菌属(Arthrobacter sp.),TEX-3芽孢杆菌属(Bacillus sp.),TEX-4红球菌属(Rhodococcus sp.),TEX-5芽孢杆菌属,(Bacillus sp.),TEX-6戈登氏菌属(Gordonia sp.) , TEX-7列契瓦尼而氏菌属(Lechevalieria sp.),并为这7种菌株建立了系统发育树。实验进一步分析得到了混合菌的最佳生长条件:培养温度30℃,培养时间为48h,接种量10%,摇床转速180 r/min。降解甲苯,乙苯的的菌种适合弱碱性环境,pH=7~9时降解率均很高,降解二甲苯的菌种适合弱酸性或弱酸性环境,pH=4或10时降解率最高。针对苯系物极易挥发和溶解度小的特点,本实验采用添加离子表面活性剂吐温80,以达到苯系物增溶效果。研究表明吐温80含量为0.3%时,混合菌对甲苯的降解率最高达98%;吐温80含量为0.4%时,乙苯最高降解率达88%;吐温80含量为0.6%时,间对二甲苯的降解率最高达78.6%,吐温80含量为0.6%时,邻二甲苯的最高降解率达76%。实验表明,一定量的吐温80可以显著提高水相中苯系物的溶解度,增大酶与底物的接触几率,提高酶的反应速度,提高生物可利用率。但吐温80浓度高于一定值后,其与底物的竞争关系加剧,进而抑制微生物对底物的降解。研究表明这些混合菌对苯系物的降解率很高,对甲苯的降解率可以达到99%,对乙苯的降解率达92%,对二甲苯的降解率维持在70~83%之间。菌落在高浓度苯系物条件下也能存活。对降解产物的GC-MS分析发现,降解过程中产生了苯酚、环已醇、1.8-壬二烯-3-醇、长链烷烃、长链烯烃、乙酸等物质,表明降解过程中苯环被打破,碳链被微生物重新组合。此与苯系物的常规降解途径有所出入,有待于进一步考证,进而为苯系物污染的生物修复和治理提供基础理论资料。更多还原

【Abstract】 Benzene (BTEX) is the main petroleum pollutants in groundwater. Microbial degradation is an effective ecological approach of benzene compounds disposal. This study selected activated sludge as a bacteria source from Shanghai Jinshan Chemical Industry Zone sewage treatment plant, toluene, ethylbenzene and xylene as substrates. Under aerobic conditions, 7 kinds of bacteria are selected that can degrade benzene compounds.Through 16SrDNA sequence test, the 7 kinds of bacteria (TEX1-7) are identified as Pseudomonas sp., Arthrobacter sp., Bacillus sp., Rhodococcus sp., Bacillus sp., Gordonia sp., and Lechevalieria sp., respectively. And then the phylogenetic tree is established. Further study shows that the optimal growth conditions for mixed bacteria are 30℃, reaction time 48h, inoculation 10%, shaking rotate 180r/min, pH=7~9 for toluene, ethylbenzene degradation and pH=4 or 10 for xylene degradation, respectively.Ionic surfactant Tween 80 is added to achieve solubilization effect. Studies have shown that the highest toluene degradation reaches to 98% at 0.3% Tween-80 content, ethylbenzene 88% at 0.4%, inter-p-xylene 78.6% and o-xylene 76% at 0.6%, respectively. A certain amount of Tween-80 can significantly improve the water solubility of benzene phase, increasing the contact probability of enzyme and substrate, then increase the enzyme reaction speed and improve bio-availability. However, excessive Tween 80 will inhibit microbial degradation of the substrate.The studies have shown that these mixed bacteria can degrade benzene compounds effectively. The biodegradation rate for toluene can reach 99%, ethylbenzene 92%, and xylene between 70-83%. Colonies can survive under high concentration of benzene compounds.GC-MS analysis of degradation products indicate that biodegradation produces phenol, cyclohexanol, 1, 8-Nonadiyne-3-ol, long-chain alkanes, long-chain olefins, etc. It is indicated that the benzene ring is broken and carbon chain is reset by these bacteria. This differs from the conventional degradation pathway. Further study is needed for the basic theory of bioremediation and control of BTEX contamination.更多还原