碱度对水产养殖絮体生物学特性及氨氮转化的影响

Effect of Alkalinity on Nitrogen Conversion and Biological Characteriztion of Bioflcs in Bioflocculation Process in Aquaculture

在异位式生物絮凝反应器中,添加鳗鲡循环水养殖系统中收集的残饵粪便进行生物絮体培养,用碳酸氢钠和1mol/L HCl控制反应器中的碱度水平(以CaCO3计)为:a组≥250mg/L、b组150~200mg/L、c组75~100mg/L,研究碱度对絮体形成过程中3种形态氮含量、絮体的氮素转化及粗蛋白、粗脂肪和胞外聚合物含量的影响,用IlluminaMiseq测序技术检测了絮体微生物群落的多样性。试验结果表明,碱度150~200mg/L试验组絮体氮素转化率[(70.84±7.67)%]、粗蛋白含量[(36.74±0.59)%]、疏松结合胞外聚合物和紧密结合胞外聚合物中蛋白质与多糖比和絮体原核、真核微生物群落Shannon多样性指数均优于其他试验组。将碱度提高至逾150mg/L,可促使反应器中的硝化作用。3组絮体中具有显著性差异的原核微生物优势菌群为变形菌门和Saccharibacteria门,3个试验组中变形菌门的比例分别为45.96%、27.81%、80.07%;絮体真核微生物具有显著性差异的优势菌群为子囊菌门和纤毛虫门,3个试验组中纤毛虫门的比例分别为7.24%、0.43%、14.85%。异位式生物絮体培养过程中碱度应控制在150mg/L以上时,絮体微生物多样性增加,氮素转化效率增高。

Sodium bicarbonate and 1 mol/L hydrochloric acid（HCl）were regularly added into a reactor containing solid wastes including feed remnants and feces collected from a system of eel Anguilla marmorata culture at various alkalinities（CaCO_3/L）of≥250in Group a,150—200in Group B and 75—100mg in Group c with three replicates to cultivate bioflocs to evaluate changes in levels of three types of nitrogen and conversion rate of nitrogen by bioflocs,and contents of crude protein,crude fat,and extracelluar polymeric substances（EPS）in the bioflocs.The diversity of microbial communities in the bioflocs was detected by Illumina Miseqsequencing technology.The results showed that there were higher nitrogen conversion rate（70.84±7.67）%,crude protein content（36.74±0.59）%and the ratio of protein and polysaccharide in loosely bound-EPS（LB-EPS）and tightly bound-EPS（TB-EPS）and higher Shannon diversity index in prokaryotic and eukaryotic microbial community in Group b than those in Group a and Group c.The nitrification was promoted in the reactor where the alkalinity was increased to above 150 mg/L（CaCO3）.Proteobacteriaand Saccharibacteria were of the dominant bacteria with significant differences in prokaryotic community in flocs of the three groups,accounting for 45.96%in Group a,27.81%in Group b,and80.07%in Group c.In eukaryotic community,however,Ascomycota and Ciliophora were the dominant bacteria with significant differences,Ciliophorarepresenting 7.24%in Group a,0.43%in Group b,and14.85%in Group c.In conclusion,the high microbial diversity,and efficiency of nitrogen conversion in bioflocculation are found in the reactor at alkalinity of over 150mg/L（CaCO3）.