State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, No. 1 West Beichen Road Chaoyang District, Beijing, 100101, People's Republic of China.
Appl Microbiol Biotechnol. 2020 Apr;104(7):3183-3192. doi: 10.1007/s00253-020-10452-y. Epub 2020 Feb 13.
Nitrate accumulation causes long-time threat to aquatic animals in recirculating aquaculture system (RAS); thus, nitrate removal is also required in RASs. However, the lack of carbon sources makes denitrification difficult to function. Nitrate removal performance of an aerobic denitrifying and extracellular polyhydroxyalkanoate depolymerase-producing bacterium, Pseudomonas sp. AOB-7, using polyhydroxyalkanoate (PHA) granules as a solid sustained-release carbon source in RAS was evaluated. With the initial nitrate-N concentration of 140 mg/L, the high denitrification rates of 0.056 g NO-N L day and 0.035 g NO-N L day were achieved in denitrification medium containing poly-β-hydroxybutyrate (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), respectively. Significant erosions and pits formed on the surface of the granules made them a good biofilm carrier for AOB-7, and 3-hydroxybutyrate (3-HB) monomer was the major product released to aquatic phase, which was benefit to animals. SEM photos showed that AOB-7 entered and attached on the inside of the PHA particle holes. A 4-week application trial was conducted to reveal the effects of PHB (AOB-7) denitrifying agent and 3-HB produced on growth of zebrafish (Brachydanio rerio) by adding 0.1% (w/v) PHB (AOB-7) denitrifying agent. Result indicated that PHB (AOB-7) denitrifying agent can significantly reduce nitrate-N content in RASs. Compared with the control group, feed coefficient ratio reduced by 18% and weight gain ratio increased by 29% in the PHB (AOB-7) denitrifying agent group. 3-HB monomer produced during the denitrification was speculated to function as a prebiotic and promote zebrafish growth. KEY POINTS: • AOB-7 showed a good aerobic denitrifying ability on PHA granules as sustained-release C source. • PHB (AOB-7) denitrifying agent can significantly reduce nitrate content in RAS. • R-3-HB monomer was the major product released to aquatic phase and function as a prebiotic.
硝酸盐积累对循环水产养殖系统 (RAS) 中的水生动物构成长期威胁；因此，RAS 中也需要去除硝酸盐。然而，缺乏碳源使得反硝化作用难以发挥作用。本文评估了好氧反硝化和胞外聚羟基烷酸酯解聚酶产生菌 Pseudomonas sp. AOB-7 利用聚羟基烷酸酯 (PHA) 颗粒作为 RAS 中固体缓释碳源的硝酸盐去除性能。在初始硝酸盐-N 浓度为 140mg/L 的情况下，在含有聚-β-羟基丁酸酯 (PHB) 和聚(3-羟基丁酸酯-co-3-羟基戊酸酯) (PHBV) 的反硝化培养基中分别实现了 0.056gNO-NLday 和 0.035gNO-NLday 的高反硝化速率。颗粒表面形成了明显的侵蚀和凹坑，使它们成为 AOB-7 的良好生物膜载体，并且 3-羟基丁酸 (3-HB) 单体是释放到水相的主要产物，这有利于动物。SEM 照片显示，AOB-7 进入并附着在 PHA 颗粒孔内。进行了为期 4 周的应用试验，通过添加 0.1%（w/v）的 PHB（AOB-7）脱氮剂来揭示 PHB（AOB-7）脱氮剂和产生的 3-HB 对斑马鱼（Brachydanio rerio）生长的影响。结果表明，PHB（AOB-7）脱氮剂可显著降低 RAS 中的硝酸盐-N 含量。与对照组相比，PHB（AOB-7）脱氮剂组的饲料系数比降低了 18%，体重增加率提高了 29%。反硝化过程中产生的 3-HB 单体被推测为一种益生元，可促进斑马鱼生长。关键点：
AOB-7 作为缓释 C 源在 PHA 颗粒上表现出良好的好氧反硝化能力。
PHB（AOB-7）脱氮剂可显著降低 RAS 中的硝酸盐含量。
R-3-HB 单体是释放到水相的主要产物，可作为益生元。
