摘要： 为提高生物絮团性能，在悬浮式生物反应器中，比较了2种生物絮团质量浓度（300 mg/L、600 mg/L）和3种枯草芽孢杆菌（Bacillus subtilis）添加量（104 CFU/mL、105 CFU/mL和106 CFU/mL）对生物絮团氨氮去除效率和絮团营养组成的影响。结果显示：生物絮团质量浓度对生物絮团氨氮去除速率有显著影响（P < 0.05），其中絮团质量浓度为600 mg/L时氨氮去除率最高，达（3.85±0.27）mg N/h。絮团质量浓度对生物絮团主要营养成分（粗蛋白、粗灰分、粗脂肪）含量和部分氨基酸含量没有显著影响（P > 0.05）。枯草芽孢杆菌添加量为106 CFU/mL时的生物絮团浓度组絮团粗蛋白含量分别为（27.22±0.47）%和（27.43±1.07）%显著高于添加量为104 和105 CFU/mL的絮团组（P < 0.05）。生物絮团质量浓度为600 mg/L时4种硝化作用功能基因（ureC, amoA, nxrA, Hao）拷贝数均高于300 mg/L组；枯草芽孢杆菌添加量为104 CFU/mL时，生物絮团nxrA基因拷贝数高于菌添加量为105和106 CFU/mL组，amoA、ureC、Hao基因拷贝低于菌添加量为105和106CFU/mL组。研究表明，生物絮团质量浓度为600 mg/L、枯草芽孢杆菌添加量为106 CFU/mL时，有利于提高生物絮团系统氨氮去除速率和粗蛋白、氨基酸含量。

关键词: 生物絮团, 枯草芽孢杆菌, 絮团浓度, 絮团营养组成, 氨氮去除

Abstract: Biofloc technology (BFT) has been proven to perform closed, high-density aquaculture at a lower cost and has received much attention from aquaculturists in recent years. The two critical services of bioflocs in BFT aquaculture systems include removing ammonia nitrogen from feeding and providing nutrients for some cultured animals. The current experiment investigated the ammonia nitrogen removal efficiency and nutrient composition of bioflocs under the condition of two bioflocs concentrations (300 mg/L and 600 mg/L) and three Bacillus subtilis additions (104 CFU/mL, 105 CFU/mL and 106 CFU/mL) in the suspended growth reactors. The results showed that the bioflocs concentration had a significant effect (P < 0.05) on the removal rate of ammonia nitrogen. The highest ammonia nitrogen removal rate was (3.85 ± 0.27) mg N/h observed in the group with 600 mg/L bioflocs and 106 CFU/mL Bacillus subtilis, which was significantly higher than that in the 300 mg/L bioflocs groups. The bioflocs concentrations had a significant effect on the major nutrients (crude protein, crude ash, crude fat) and some amino acids in the bioflocs. There was no significant effect of bioflocs concentrations on the content of major nutrients (crude protein, crude ash, crude fat) and some amino acids in the bioflocs (P > 0.05). The crude protein content of the bioflocs was (27.22±0.47)% and (27.43±1.07)% for the 300 mg/L and 600 mg/L bioflocs groups with the Bacillus subtilis addition level of 106 CFU/mL, which was significantly higher than the other two bacteria addition levels. The copy numbers of four nitrification genes (ureC, amoA, nxrA, Hao) were higher in the groups at a concentration of 600 mg/L than in the 300 mg/L groups. The copy numbers of amoA, ureC and Hao genes in bioflocs increased with the addition of Bacillus subtilis. The results of the current study proved that the 600 mg/L bioflocs and 106 CFU/mL Bacillus subtilis were beneficial to improve the ammonia nitrogen removal rate and nutritional content of the bioflocs. 

Key words: Biofloc technology, Bacillus subtilis, biofloc levels, ammonia removal, biofloc nutritional components