源自生物絮团产絮凝剂的异养硝化-好氧反硝化菌xt1的鉴定及其脱氮特性

为了高效进行水体脱氮,本实验从形成于凡纳滨对虾(Litopenaeus vannamei)养殖水体的生物絮团中分离到一株具产絮能力的脱氮菌xt1,经16S r RNA基因测序与生理生化分析确定菌株xt1为短小芽孢杆菌(Bacillus pumilus)。在此基础上,本文研究了该菌的脱氮特性。结果表明:菌株xt1最佳碳源为葡萄糖,以其为底物对氨氮、硝态氮去除率分别达95.56%和57.40%。以蔗糖为碳源亦具较高脱氮率,对氨氮、硝态氮去除率分别达69.95%和49.50%;该菌能利用有机氮加速生长,添加0.25%、0.5%、1%和2%的蛋白胨能促进OD600,分别达到0.925、1.034、1.103和1.314,均高于未加蛋白胨下的生长,且氨氮去除率均超过90%,硝态氮去除率均超过88%;该菌能适应20—200mg/L无机氮浓度;该菌能以NH4+-N、NO2–-N或NO3–-N为唯一氮源进行异养硝化-好氧反硝化,反应84h去除率分别达到94.16%、47.60%和91.17%。其中,该菌的硝化形式是将氨氮转化为气态氮脱除,其硝态氮反硝化形式是先将硝态氮转化为亚硝氮,再以气态氮脱除。在进行异养硝化-好氧反硝化同时,菌株xt1体现絮凝特性,絮凝率最高分别达到82.28%、73.15%和75.60%;此外,添加该菌于养殖水体中能加速生物絮团形成,同时提高脱氮率。各项结果表明,菌株xt1可作为水产养殖水体脱氮的备选菌株。

IDENTIFICATION AND NITROGEN REMOVAL CHARACTERISTICS OF A HETEROTROPHIC NITRIFICATION-AEROBIC DENITRIFICATION STRAIN xt1 WITH FLOCCULATION ABILITY ISOLATED FROM BIOFLOC

A nitrogen removal strain xt1 with flocculation ability was isolated from biofloc in aquaculture wastewater of Litopenaeus vannamei. The results of molecular biological, physiological, and biochemical identification showed that the strain xt1 was Bacillus pumilus. On this basis, the nitrogen removal characteristics of this strain were studied. The results show that the best carbon source of the strain xt1 was glucose. The removal rate of ammonia and nitrate was 95.56% and 57.40% with glucose as substrate, and when sucrose was used as the carbon source, the removal rates of ammonia and nitrate reached 69.95% and 49.50%, respectively. The strain could use organic nitrogen to accelerate the growth. When 0.25%, 0.5%, 1% and 2% peptone were added, OD₆₀₀ was increased to 0.925, 1.034, 1.103 and 1.314, respectively, in which the removal rate of ammonia was more than 90%, the removal rate of nitrate was over 88%. The strain could adapt to the concentration of 20-200mg/L inorganic nitrogen. The strain could use NH₄⁺-N, NO₂^--N or NO₃-N as a sole nitrogen source, and the removal efficiency reached 94.16%, 47.60% and 91.17% within 84h, respectively. Among them, the nitrifying form of the strain was the conversion of ammonia into gaseous nitrogen. The form of nitrate denitrification was converted to nitrate into nitrite, and then to gaseous nitrogen. In the process of heterotrophic nitrification-aerobic denitrification, the strain xt1 showed flocculation characteristics, and the highest flocculation rate reached 82.28%, 73.15%, and 75.60%, respectively. Besides, the addition of strain xt1 in the wastewater could accelerate the formation of biofloc and increase the rate of nitrogen removal. Therefore, strain xt1 can be used as an alternative strain for nitrogen removal from aquaculture wastewater.