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首页> 外文期刊>Applied Microbiology and Biotechnology >Anaerobic dechlorination of carbon tetrachloride by free-living and attached bacteria under various electron-donor conditions
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Anaerobic dechlorination of carbon tetrachloride by free-living and attached bacteria under various electron-donor conditions

机译：在各种电子给体条件下自由活动和附着细菌对四氯化碳的厌氧脱氯

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摘要

The dechlorination of carbon tetrachloride (CCl4) by free-living and attached bacteria under anaerobic conditions was studied to examine the relationship between porous media and electron donor. Two batch-type experiments, the free-living and attached bacterial systems, were conducted with and without addition of 0.5-mm glass beads. Glucose and acetate were selected as the primary electron donors because they are easily biodegradable. Direct epifluorescence technology, the DAPI (4' 6-diamidino -2-phenylindole) method, was used for counting the microbial activities. Adding glass beads could accelerate the dechlorination rate of CCl4. Removals of 44%-57% were observed in free-living bacterial system. Whereas a two- to fivefold increase in the CCl4 dechlorination rate was observed in the attached system. Experimental results and thermodynamic calculations indicated that glucose is a better supplementary substrate than acetate for stimulating the dechlorinating capability of microorganisms because of its relatively high available free energy. A higher concentration of substrate provided more reducing power for attached bacteria to initiate the dechlorination reaction. The pseudo-first-order rate constants of CCl4 dechlorination ranged from 0.007 day(-1) to 0.017 day(-1) and from 0.011 day(-1) to 0.0625 day(-1) for free-living and attached bacterial systems respectively. Microscopic observation revealed a three- to eightfold difference of microbial number between the free-living and attached bacterial systems. On the basis of the results in this study, we can conclude that the presence of porous media and an electron donor can change the dechlorination capabilities of the microorganisms. This work will be valuable in the design of in situ bioremediation as it discusses the specific area of the medium and supplementation with an electron donor to stimulate the indigenous microflora.
机译：研究了厌氧条件下自由活动和附着细菌对四氯化碳（CCl4）的脱氯作用，以研究多孔介质与电子给体之间的关系。在添加和不添加0.5 mm玻璃珠的情况下，进行了两个批处理型实验，即自由活动和附着的细菌系统。选择葡萄糖和乙酸盐作为主要的电子供体，因为它们易于生物降解。使用直接表面荧光技术DAPI（4'6-二mid基-2-苯基吲哚）方法来计数微生物活性。添加玻璃珠可以加快CCl4的脱氯速度。在自由生活的细菌系统中观察到去除44％-57％。而在连接系统中，CCl4的脱氯速率增加了2到5倍。实验结果和热力学计算表明，葡萄糖在刺激微生物的脱氯能力方面比乙酸盐更好，因为它具有较高的可用自由能。较高浓度的底物为附着的细菌引发脱氯反应提供了更大的还原能力。对于自由活动和附着细菌系统，CCl4脱氯的伪一级速率常数分别为0.007天（-1）至0.017天（-1）和0.011天（-1）至0.0625天（-1）。 。显微镜观察显示，自由生活和附着的细菌系统之间的微生物数量相差三到八倍。根据这项研究的结果，我们可以得出结论，多孔介质和电子给体的存在可以改变微生物的脱氯能力。这项工作在原位生物修复的设计中将是有价值的，因为它讨论了培养基的特定区域并补充了电子供体以刺激本土微生物群落。

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