低营养水体中芽孢杆菌降解有机氮的研究

芽孢杆菌具有降解有机氮的功能,但在养殖水体等低营养水体中,其降解效果可能受到影响.为研究低营养水体中有机氮的降解情况,通过模拟凡纳滨对虾中间培育过程配制低营养水体,分别接种芽孢杆菌NT9和YB3(NT9水体和YB3水体),然后研究水体中微生物的生长与有机氮的降解情况,并构建数学模型进行分析.结果显示,起始接种量为10×10~5 cfu·mL~(-1)时,NT9水体总菌量呈下降趋势,平均为(3.46×10~5±2.39×10~5) cfu·mL~(-1),YB3水体总菌量则上升到(25.43×10~5±8.84×10~5) cfu·mL~(-1),但均高于未接种的对照水体.NT9水体和YB3水体的有机氮降解率显著高于对照水体(p0.05),分别提高50.28%和119.41%,降解速率也分别提高65.22%和121.74%.对照水体、NT9水体和YB3水体单位菌量的有机氮降解效率分别为1.238、1.649和1.904 mg·L~(-1),降解模型分别为y=-6.40+1.39x_1+1.45x_2、y=2.11+8.21x_3-0.64x_4-1.26x_1x_3-0.32x_2x_4和y=1.73+6.11x_2(x_1、x_2、x_3、x_4分别表示总菌量、总菌增量、有机氮含量和时间).研究表明,在低营养水体中接种芽孢杆菌有利于有机氮的降解,但不同的菌株具有不同的降解模式,菌株YB3为能够适应低营养水平、增殖能力较强的菌株,可以更有效地促进有机氮的降解,提高降解效率.

Organic nitrogen removal by Bacillus strains in water body under low nutrition level

Strains of Bacillus sp. are common probiotics with organic nitrogen (Org-N) degrading function. However the efficiency would be compromised under low nutrient level, such as aquaculture water body. For investigating the degradation of Org-N in such water, two Bacillus strains of NT9 and YB3 were inoculated into microcosm aquaculture water simulated according to the nursery process of Litopenaeus vannamei postlarvae, and the water bodies were named as NT9-WB and YB3-WB, respectively. Thereafter, the growth of microorganism and the degradation of Org-N in those two water bodies were determined, and statistic models were constructed to explore the possible approaches for improving Org-N degradation. Results showed that with a initial inoculation content of 10×10⁵ cfu·mL^-1, the mean microbial colonies in the NT9-WB declined to (3.46×10⁵±2.39×10⁵) cfu·mL^-1, and elevated to (25.43×10⁵±8.84×10⁵) cfu·mL^-1 in the YB3-WB, both of which were all higher than that in the control water body (C-WB) without inoculation of strain. The degraded ratios of Org-N in both NT9-and YB3-WB were significantly higher than that in C-WB (p<0.05), increased by 50.28% and 119.41%, respectively. Furthermore, the Org-N degrading rates of NT9-WB and YB3-WB also elevated 65.22% and 121.74%, respectively, when compared to C-WB. In C-, NT9-and YB3-WB, the degrading rates were 1.238, 1.649, 1.904 mg·L^-1 per unit of colony forming units (cfu), and the Org-N degradation models were y=-6.40+1.39x₁+1.45x₂, y=2.11+8.21x₃-0.64x₄-1.26x₁x₃-0.32x₂x₄ and y=1.73+6.11x₂ (x₁, x₂, x₃ and x₄ represented cfu, cfu increment, Org-N concentration and time), respectively. In conclusion, both Bacillus strains improved the degradation of Org-N in low nutrient level water, but with different degrading style, and the strain YB3 had a high adaptation ability to low nutrient level and could elevate the degradation of Org-N more efficiently.