Schröder TJ, Stams AJM, Schraa G, Field JA
Department of Biomolecular Sciences, Laboratory of Microbiology, Wageningen Agricultural University, 6703 CT Wageningen, The Netherlands.
Appl Environ Microbiol. 1998 Jul 1;64(7):2350-6. doi: 10.1128/AEM.64.7.2350-2356.1998.
The potential of granular sludge from upflow anaerobic sludge blanket (UASB) reactors for bioremediation of chlorinated pollutants was evaluated by using carbon tetrachloride (CT) as a model compound. Granular sludges cultivated in UASB reactors on methanol, a volatile fatty acid mixture, or sucrose readily degraded CT supplied at a concentration of 1,500 nmol/batch (approximately 10 µM) without any prior exposure to organohalogens. The maximum degradation rate was 1.9 µmol of CT g of volatile suspended solids-1 day-1. The main end products of CT degradation were CO2 and Cl-, and the yields of these end products were 44 and 68%, respectively, of the initial amounts of [14C]CT and CT-Cl. Lower chlorinated methanes accumulated in minor amounts temporarily. Autoclaved (dead) sludges were capable of degrading CT at rates two- to threefold lower than those for living sludges, indicating that abiotic processes (mediated by cofactors or other sludge components) played an important role in the degradation observed. Reduced components in the autoclaved sludge were vital for CT degradation. A major part (51%) of the CT was converted abiotically to CS2. The amount of CO2 produced (23%) was lower and the amount of Cl- produced (86%) was slightly higher with autoclaved sludge than with living sludge. Both living and autoclaved sludges could degrade chloroform. However, only living sludge degraded dichloromethane and methylchloride. These results indicate that reductive dehalogenation, which was mediated better by living sludge than by autoclaved sludge, is only a minor pathway for CT degradation. The main pathway involves substitutive and oxidative dechlorination reactions that lead to the formation of CO2. Granular sludge, therefore, has outstanding potential for gratuitous dechlorination of CT to safe end products.
以上流式厌氧污泥床（UASB）反应器颗粒污泥对氯代污染物进行生物修复的潜力，以四氯化碳（CT）作为模型化合物进行了评估。在UASB反应器中，以甲醇、挥发性脂肪酸混合物或蔗糖为底物培养的颗粒污泥，能够在未预先接触有机卤化物的情况下，轻易降解以1500 nmol/批次（约10 µM）浓度供应的CT。最大降解速率为1.9 µmol CT·g挥发性悬浮固体-1·天-1。CT降解的主要终产物是CO2和Cl-，这些终产物的产率分别为初始[14C]CT和CT-Cl量的44%和68%。低氯代甲烷会少量暂时积累。经高压灭菌（死亡）的污泥降解CT的速率比活性污泥低两到三倍，这表明非生物过程（由辅因子或其他污泥成分介导）在观察到的降解中起重要作用。高压灭菌污泥中的还原成分对CT降解至关重要。CT的一大部分（51%）通过非生物方式转化为CS2。与活性污泥相比，高压灭菌污泥产生的CO2量（23%）更低，产生的Cl-量（86%）略高。活性污泥和高压灭菌污泥都能降解氯仿。然而，只有活性污泥能降解二氯甲烷和氯甲烷。这些结果表明，活性污泥介导的还原脱卤比高压灭菌污泥介导的更好，但这只是CT降解的次要途径。主要途径涉及导致CO2形成的取代和氧化脱氯反应。因此，颗粒污泥在将CT免费脱氯为安全终产物方面具有突出潜力。
