一株好氧反硝化菌的筛选鉴定及其条件优化

Screening identification and optimal biodegradation conditions of new aerobic denitrifying bacteria

在上海境内苏州河污染较严重的武宁路段和浙江路段采取水样,对其进行反硝化菌的专性筛选及条件优化,得到菌种N-4。结果表明:N-4菌反应最佳初始pH值为7.5,最适宜的温度为30℃,最佳接种量为20%,最佳碳源为葡萄糖。在最优条件下,16 h内反硝化的最佳降解率为87.6%。经16S rDNA序列鉴定N-4菌为克雷伯氏菌属的解鸟氨酸克雷伯菌(Klebsiella ornithinolytica),革兰氏染色呈阴性。

This paper is aimed to introduce the screening process and optimization of the biodegradation conditions of a new efficient aerobic denitrifying bacterium. The aerobic denitrifying bacteria N-4 was extracted from the water samples of Wuning section and Zhejiang section of Suzhou River in Shanghai. The results of biomass and denitrification test indicated that the optimum degradation conditions of the strain N-4 can be stated as follows： the best temperature was 30 degrees Celsius, the denitrification efficiency decreased rapidly when the temperature exceeded 30 degrees Celsius; the best pH value was 7.5 with a high biomass between 7 and 7.5. The best inoculums＇ size was 20% and there was no change when it was more than 20%. Nevertheless, in practice, large amount of 20% vaccination can be reduced to 5% and it brings no significant impact to the degradation processing provided the denitrification extends to five hours. The best carbon source was glucose; it was consistent with the characteristics of Klebsiella. Under the conditions motioned above, the degradation rate could reach 87.6% within 16 hours. Through the analysis, the bacteria N-4 was identified as Klebsiella ornithinolytica where under an electron microscope, it was observed as short stubby bacilli with a separate arrangement, no spores, no flagellum, about 0.8 1.5 microns in length and about 0.3-0.6 microns in diameter. The colonies were off-white round and it was a Gram-negative bacterium. The strain was found in other domestic waters as glycogen accumula- ting organisms. The Klebsiella strains with denitrifying function was rarely reported in the literature. It can survive in the culture medium from weeks to several months and it can be killed in 30 minutes at 55 degrees, to ensure the application prospect with ecological safety. In this study, the direct sampling from heavily polluted Suzhou creek is equivalent to the natural domestication process. Hence, the screening process is far more time efficient than SBR sludge domestication. However, the river has too much of its liquidity uncertainties. Therefore, it still needs to consider many aspects and require further research.