Basic Study On Degradation Of Residual Bait In Aquaculture Water By Acinetobacter Junii And Its Application

The soluble starch and protein in the residual bait are difficult to be removed by physical filtration,which is one of the main factors leading to the pollution of aquaculture effluent.The effective degradation of soluble starch and protein is the key to ensure the effluent to meet the discharge standard.In this experiment,Acinetobacter immobilized on volcanic rock was used to degrade the residual bait in wastewater,and its degradation performance of soluble starch and protein in the residual bait was tested in order to achieve the purpose of purification of aquaculture effluent.The results showed that Acinetobacter can degrade residual bait efficiently.Under the optimum conditions(Initial concentration of residual bait 10.0 mg/m L containing 4.0 mg/ml soluble protein and 4.5 mg/m L soluble starch;30?;p H 7.0),the degradation rate of soluble protein and soluble starch can reached to 88.9% and 91.4% respectively,and the COD of residual bait wastewater is reduced by 76.6% after about 144 h degradation.The optimal conditions of immobilized Acinetobacter are similar to those of free Acinetobacter,but the degradation effect is more significantly.Under the optimum conditions,the degradation rates of soluble protein and soluble starch can reach 90.9% and 97.3% respectively after 120 hours.COD can be reduced by 92.7%.In addition,the degradation rate of soluble protein and soluble starch by free Acinetobacter at high temperature and low temperature can be maintained at a high level respectively(20?: 82.3% 65.3%;40?: 74.7% 73.7%);When the salt content less than10.0 g/L,more than 45.8% soluble protein and soluble starch can be removed;It indicating that the Acinetobacter has a wide ecological range of adaptation to temperature and salinity.The Acinetobacter is relatively sensitive to the acidic and alkaline environment.When p H is 5.0,the degradation rate of protein and starch is only 34.3% and 13.1%,and when p H is9.0,the degradation rate of protein and starch is only 48.0% and 42.4% respectively;COD removal rate is 43.1%(p H:5.0)and 55.9%(p H:9.0).The immobilization treatment improved the environmental adaptability of the bacteria.Under the conditions of p H 6.0-8.0,temperature 20-40?,salt content less than 10.0 g/L,the degradation rates of soluble protein and soluble starch were maintained above 79.8% and 71.7%,and could be reused for at least 9 cycles.The results of the degradation experiment of the residual bait in the raw water showed that the Acinetobacter could reproduce steadily in the raw water and had good environmental competitiveness.The degradation rates of soluble protein by free and immobilized Acinetobacter were as high as 89.7% and 94.7%,and the degradation rates of soluble starch were 90.9% and 94.5%,and the removal rates of COD were 76.3% and 83.1%respectively.The addition of free and immobilized Acinetobacter to the raw water can significantly improve the degradation efficiency of the residual bait,indicating that Acinetobacter will have a wide application prospect in aquaculture production.