Deniz Timur, Cinar Ozer, Marques Ana C, Grady C P Leslie
Department of Environmental Engineering and Science, Clemson University, South Carolina 29634-0919, USA.
Water Environ Res. 2006 Apr;78(4):340-52. doi: 10.2175/106143005x89986.
The response of a mixed microbial culture to cyclic aerobic and anoxic (denitrifying) conditions was studied in a chemostat with a 48-hour hydraulic residence time receiving a feed containing benzoate and pyruvate. When the cyclic conditions were 3-hour aerobic and 9-hour anoxic, the bacteria-degraded benzoate aerobically via the catechol 2,3-dioxygenase (C23DO) pathway. The quantity of C23DO remained constant throughout the anoxic period but decreased during the initial portion of the aerobic period before returning to the level present in the anoxic period. Anoxic biodegradation of benzoate was via benzoyl-CoA reductase, which remained constant regardless of the redox condition. The aerobic benzoate uptake capability (AeBUC) of the culture increased during the aerobic period but decreased during the anoxic period. The anoxic benzoate uptake capability (AnBUC) exhibited the opposite response. When the cycle was 6-hour aerobic and 6-hour anoxic, aerobic biodegradation of benzoate proceeded via the protocatechuate 4,5-dioxygenase (P45DO) pathway. The P45DO activity decreased early in the aerobic period, but then increased to the level present during the anoxic period. The level of benzoyl-CoA reductase was constant throughout the cycle. Furthermore, AeBUC and AnBUC responded in much the same way as in the 3/9-hour chemostat. During a 9-hour aerobic and 3-hour anoxic cycle, the culture synthesized both P45DO and C23DO, with the former having significantly higher activity. Unlike the other two cycles, AeBUC changed little during the aerobic period, although AnBUC decreased. The culture was well-adapted to the cyclic conditions as evidenced by the lack of accumulation of either substrate during any cycle tested. This suggests that cyclic aerobic-anoxic processes can be used in industrial wastewater-treatment facilities receiving significant quantities of simple aromatic compounds like benzoate. However, the results showed that the kinetics of benzoate degradation were different under aerobic and anoxic conditions, a situation that must be considered when modeling cyclic bioreactors receiving aromatic compounds.
在一个水力停留时间为48小时、接收含有苯甲酸盐和丙酮酸进料的恒化器中，研究了混合微生物培养物对循环好氧和缺氧（反硝化）条件的响应。当循环条件为3小时好氧和9小时缺氧时，细菌通过儿茶酚2,3-双加氧酶（C23DO）途径好氧降解苯甲酸盐。C23DO的量在整个缺氧期保持恒定，但在好氧期的初始阶段下降，然后恢复到缺氧期的水平。苯甲酸盐的缺氧生物降解是通过苯甲酰辅酶A还原酶进行的，无论氧化还原条件如何，该酶都保持恒定。培养物的好氧苯甲酸盐摄取能力（AeBUC）在好氧期增加，但在缺氧期下降。缺氧苯甲酸盐摄取能力（AnBUC）表现出相反的响应。当循环为6小时好氧和6小时缺氧时，苯甲酸盐的好氧生物降解通过原儿茶酸4,5-双加氧酶（P45DO）途径进行。P45DO活性在好氧期早期下降，但随后增加到缺氧期的水平。苯甲酰辅酶A还原酶的水平在整个循环中保持恒定。此外，AeBUC和AnBUC的响应与在3/9小时恒化器中的响应非常相似。在9小时好氧和3小时缺氧循环中，培养物合成了P45DO和C23DO，前者具有明显更高的活性。与其他两个循环不同，AeBUC在好氧期变化不大，尽管AnBUC下降。在所测试的任何循环中，两种底物均未积累，这表明培养物对循环条件具有良好的适应性。这表明循环好氧-缺氧工艺可用于接收大量简单芳香化合物（如苯甲酸盐）的工业废水处理设施。然而，结果表明，苯甲酸盐在好氧和缺氧条件下的降解动力学不同，在对接收芳香化合物的循环生物反应器进行建模时，必须考虑这种情况。
