不同碳源下硫还原地杆菌对反硝化过程的影响机制探讨

硝酸盐是废水中常见的污染物,其具有较高的氧化还原电位,在水中的去除主要依靠微生物的反硝化作用.目前的初步研究表明,电活性细菌能够和反硝化细菌通过互营生长加速反硝化过程.为探究在不同外加碳源下电活性细菌对反硝化过程的影响,选取不能够利用硝态氮作为电子受体的模式电活性细菌硫还原地杆菌(G.sulfurreducens PCA)与不同碳源(乙醇、丙酸或葡萄糖)驯化得到的反硝化细菌进行共培养.结果表明,改变碳源为乙酸盐后,不同体系中硝态氮的去除效率达到了94%.碳源的改变造成了不同程度的反硝化滞后现象,在当以乙醇为外加碳源时,G.sulfurreducens PCA的加入能够将迟滞时间缩短3 h,其反硝化速率可达到186 g·m~(-3)·d~(-1),同时产生的亚硝氮含量也相对最低.但以葡萄糖作为反硝化外加碳源时,迟滞时间最短,但加入G.sulfurreducens PCA后会延长反硝化所需的时间,这可能是与反硝化细菌同G.sulfurreducens PCA竞争体系中的乙酸盐碳源有关.分析微生物群落结构变化发现,G.sulfurreducens PCA的加入提高了反硝化细菌的相对丰度,使其能够适应因碳源改变而产生的对反硝化细菌的生长抑制现象.

The influential mechanism of Geobacter sulfurreducens on anaerobic denitrification under different carbon sources

Nitrate is considered to be a kind of usual contamination in the polluted water with high redox potential. Its removal in water mainly depends on microbial denitrification. The current preliminary study shows that electroactive bacteria can promote the denitrification process through mutual growth with denitrifying bacteria. In order to investigate the influential mechanism of the electroactive bacteria on anaerobic denitrification under different carbon sources, here, the co-culture of denitrifiers which domesticated with ethanol, propionic acid and glucose as the external carbon sources and Geobacter sulfurreducens PCA which cannot denitrify was selected to investigate the effect of interspecies interaction between the two bacteria on denitrification process. The result shows that the degradation efficiency of the nitrate after changing the carbon sources to acetate in different groups is 94%. However, there will be different lag time of denitrification when changing the carbon sources. When we use ethanol as the eternal carbon sources, the mutual growth of G. sulfurreducens PCA and denitrifying bacteria can reduce this hysteresis for 3 hours, and the rate of the denitrification can reach 186 g·m^-3·d^-1, meanwhile, the production of the nitrite is relatively low. When glucose is used as the external carbon source, the lag time is the shortest but the co-culture of the Geobacter sulfurreducens PCA and the denitrifiers extend the period of the denitrification which may be due to the competition of the acetate carbon source between the denitrifying bacteria and PCA. By analyzing the changes in microbial community structure, the co-culture with G. sulfurreducens PCA increased the relative abundance of denitrifying bacteria, enabling them to adapt to the growth inhibition caused by carbon source changes.