凡纳滨对虾循环水养殖系统生物膜反硝化菌研究

Denitrifying Microorganisms on Suspended Carrier Biofilm in a Recirculating Aquaculture System of Pacific White Shrimp Litopenaeus vannamei

硝态氮去除对于养殖尾水再利用及达标排放具有重要意义。为探明凡纳滨对虾循环水养殖系统中移动床生物反应器的反硝化潜力和氮代谢通路特征,对其表面生物膜菌群结构和反硝化效率进行分析。Illumina测序结果显示:所有样本优势菌门均为变形菌门(20.31%~25.36%)和拟杆菌门(14.42%~24.28%);在属水平上,红球菌属(0.28%~0.97%)、副球菌属(0.50%~0.99%)和假单胞菌属(0.15%~0.30%)等好氧反硝化菌主要负责硝态氮还原。实时荧光定量PCR结果显示,生物膜中反硝化功能基因nirK基因丰度高于nirS基因和nosZ基因,nirK型反硝化微生物是主要的反硝化微生物类群。原核生物功能注释结果表明,生物膜中存在活跃的异养反硝化代谢途径,可能受制于有限碳源,反硝化菌之间,及其和生物膜优势菌属之间以竞争关系为主。厌氧脱氮模拟试验表明,在不添加碳源条件下,填料生物膜可将对虾养殖水体硝态氮去除98.07%。基于上述氮代谢通路特征,本试验进一步提出短程反硝化-厌氧氨氧化对虾养殖废水硝态氮去除优化策略。此结果为深入理解循环水养殖系统氮素代谢通路及未来管理、利用填料生物膜内源性碳源和潜在反硝化功能提供理论依据。

To understand the nitrate reduction potential and nitrogen metabolism pathway character of moving bed bioreactor in a Pacific white shrimp Litopenaeus vannamei in a recirculating aquaculture system(RAS),the microbial community structure and denitrification efficiency of biofilms were analyzed on the surface of suspended carriers.Illumina sequencing results revealed that Proteobacteria(20.31%—25.36%)and Bacteroidetes(14.42%—24.28%)were dominant in all samples.At the genus level,aerobic denitrifiers such as Rhodococcus(0.28%—0.97%),Paracoccus(0.50%—0.99%)and Pseudomonas(0.15%—0.30%)were primarily responsible for nitrate reduction.Furthermore,qRT-PCR detection showed that the denitrification functional gene nirK was more abundant than that of nirS and nosZ,so the predominant denitrification bacteria were of the nirK-type.The prediction results from functional annotation of prokaryotic taxa(FAPROTAX)confirmed the presence of active heterotrophic denitrification in biofilms,the denitrifying bacteria were mainly competitive with each other and with the dominant biofilm bacteria,possibly due to the limited carbon sources.The anaerobic nitrogen removal tests showed that there was nitrate removal efficiency of up to 98.07%,without adding any carbon source.Based on the characteristics of nitrogen metabolism pathway,the partial denitrification-anammox process for shrimp aquaculture wastewater nitrogen removal was further proposed.The finding provides novel insights into comprehending of nitrogen metabolic pathways in RAS and future management,utilization of endogenous carbon sources in the biofilms,and potential denitrification functions.