硝化型和光合自养型生物絮团对泥鳅生长、肠道菌群和水体微生物群落结构的影响

为了解硝化型和光合自养型生物絮团对于泥鳅(Misgurnus anguillicaudatus)的养殖效果, 设置清水组(CW 组)、硝化组(BFT 组)和光合自养组(ABFT 组)生物絮团养殖泥鳅 45 d, 比较泥鳅的生长和消化酶活性、两类絮团的营养组成情况, 以及养殖水体和泥鳅肠道微生物的群落结构。结果显示, BFT 组和 ABFT 组的饲料转化率、特定生长率和末均重没有显著性差异(P＞0.05)。与 CW 组相比, 两实验组的饲料转化率显著降低; BFT 组的终末密度与 CW 组相比没有显著性差异(P＞0.05)。与 CW 组相比, BFT 组和 ABFT 组生物絮团可以提供(36.69±1.17)%和 (40.20±1.05)%的粗蛋白; 与 BFT 组相比, ABFT 组的生物絮团粗脂肪含量显著提高(P＜0.05), 并且促进脂肪酸由饱和向不饱和转化。ABFT 的泥鳅胰蛋白酶和脂肪酶的活性显著高于另外两组(P＜0.05)。微生物群落分析表明, 添加藻类对成熟生物絮团 Alpha 多样性指数、群落门水平和属水平没有显著影响。泥鳅摄食生物絮团会导致肠道菌群 sobs 指数显著降低。BFT 组肠道的优势菌群为变形菌门(Proteobacteria)、放线菌门(Actinobacteriota)和绿弯菌门 (Chloroflexi); ABFT 组为变形菌门和蓝藻门(Cyanobacteria)。属水平上, ABFT 组检测到高水平的气单胞菌属 (Aeromonas)。本研究表明, 硝化型和光合自养型生物絮团养殖均适合作为泥鳅绿色健康养殖的新模式。

Effects of nitrification and photosynthetic autotrophic bioflocs on the growth, gut microbiome, and microbial community structure of Loach (Misgurnus anguillicaudatu)

Biofloc technology (BFT), which is a recirculating aquaculture system, can significantly enhance nutrients and waste recycling. In addition, heterotrophic microorganisms in the BFT system can convert nitrogenous waste and residual bait produced by the metabolism of the culture species into nutrients, thereby reducing feed requirements. BFT systems are divided into three types based on the circulation of nitrogen: chemoautotrophic, heterotrophic and photoautotrophic. Common bioflocs are mainly chemoautotrophic, and control toxic nitrogen through nitrification. Additional sugars were supplemented to increase the C/N ratio to synthesize the nitrogen source into the biomass through assimilation. The bioflocs of these two energy metabolic pathways have been extensively studied. However, algae often play a prominent role in natural biofloc communities that cannot be explained simply by chemoautotrophy and heterotrophy. Algae absorb CO₂ through photosynthesis to produce O₂ and organic matter that can be used by bacteria. Moreover, it can utilize nitrate produced by nitrite-oxidizing bacteria as a nutritional substrate to support their growth. Loach (Misgurnus anguillicaudatus) is an important freshwater species farmed in China. Traditional loach breeding techniques include pond, paddy, and cage farming. However, these farming methods rely on a substantial quantity of water to manage nitrogen-containing waste in the water body, which places great pressure on the environment and hinders the sustainable, eco-friendly development of aquaculture. To understand the breeding effects of nitrification and photoautotrophic bioflocs as compensatory nutrients, loach was grown in two types of bioflocs for 45 days. Growth performance, digestive enzyme activity, community structure of the water column, as well as gut microbiome and nutritional composition of the two types of flocs were compared. Nitrification and photoautotrophic groups significantly reduced the feed conversion rate compared with the clear water group. Meanwhile, the ABFT group exhibited an enhanced absorption of nitrate (40.93%) and phosphate (37.47%), compared with the BFT group. No significant differences was observed in feed conversion and specific growth rates, or mean final weight between the two groups. The mean final weight of both groups was reduced by 10% and no significant difference was observed in the final density of the nitrification group compared to that of the clear-water group. Nitrification and photoautotrophic bioflocs could provide 36.69±1.17% and 40.20±1.05% of crude protein, respectively. Photoautotrophic bioflocs increased crude fat content and promoted the conversion of saturated to unsaturated fatty acids. The higher protein and crude fat contents of the photoautotrophic group promoted the activity of trypsin and lipase in this group of loaches. Microbial community analysis showed that the addition of algae had no significant effect on the alpha diversity index of mature bioflocs at the phylum or genus level. The ingestion of bioflocs by loaches resulted in a significant decrease in the sobs index of the intestinal flora. The dominant intestinal flora in the nitrification group were Proteobacteria, Actinobacteria, and Chloroflexi, and those in the photoautotrophic groups were Proteobacteria and Cyanobacteria. Increased concentrations of Aeromonas were observed in the ABFT group at the genus level. The high abundance of Aeromonas may have disrupted the balance of the intestinal flora of loaches in the ABFT group, leading to a lower survival rate. Additionally, the bacterial flora detected in both the water and gut reflected the influence of bioflocs on the gut health of the loaches. By substituting a portion of the feed with nitrification and photoautotrophic biofloc, it is possible to partly reduce the feed and most of the water treatment costs, which in turn, lowers the feed conversion rate. Therefore, both types of flocs demonstrate practical value in the breeding of specific species such as loaches. This study establishes a theoretical basis for advancing the integration of specialized aquatic products with innovative farming models.