WATER PURIFICATION PERFORMANCE AND FEED POTENTIAL OF BIOFLOCS INOCULATED WITH TWO BENEFICIAL BACTERIA

In order to improve the efficiency of utilizing the new flocculent forming bacterium Pseudoduganella eburnea YN12 (YN) in the production of bioflocs from aquaculture wastewater, and to utilize the flocs as feed, the feasibility of feeding the Claris fuscus was explored. The study focused on bioflocs systems, and involved the inoculation and formulation of activated sludge (AS), Pseudomonas eburnea YN12, and Bacillus subtilis (BS) into 7 groups (AS, YN, BS, AS+YN, AS+BS, YN+BS, and AS+YN+BS). The purpose of this experiment was to analyze the differences in floc morphology and structure, as well as to evaluate the most effective combination in terms of nitrogen removal efficiency and microbial community structure advantages in simulated aquaculture tail water. Finally, the optimal combination of bioflocs was collected, dried and ground into powder and added to commercial feed granulation. They were divided into two groups: the control group and the biofloc group, to explore the effects on the growth performance, feed utilization rate, muscle nutrient composition, and liver digestive and immune enzyme activities of catfish. The results showed that the water purification effect of YN+BS group was stable, the total nitrogen removal effect was good (89.6%), and the accumulation of ammonia nitrogen, nitrite and nitrate was low. The group exhibited favorable floc formation (9.0 ml/L) and had dominant denitrification bacteria (47.5%) (including Hydrogenophaga, Flavobacterium, Pseudoxanthomonas, Burkholderiae, Comamonas, Acinetobacter, etc.). The biofloc powder was mixed with commercial feed at a 5% ratio and used for Claris fuscus breeding after grinding and granulation. It was found that the growth performance of Claris fuscus including survival rate: (100±0.00)%>(95±0.00)%; weight gain: (2.81±0.35) g>(2.52±0.52) g; lenght gain: (1.68±0.36) cm>(1.51±0.34) cm and feed conversion rate (55±0.03>46±0.12) were better than those of the control group of pure commercial feed. However, amylase, immune enzymes, including catalase, superoxide dismutase, glutathione peroxidase and other delicious amino acids in muscle nutrition, including glutamic acid, aspartic acid, alanine and glycine, were lower than those in the control group. The bioflocs feed from YN+BS group had a good advantage in growth performance of catfish, but not in digestion ability, immune activity, and muscle nutrient composition. Therefore, it is necessary to further adjust the level of biofloc addition to optimize the feeding effect of Claris fuscus.