Preparation Of Probiotic-Loaded Montmorillonite And Its Application In Tilapia Culture

The control and bioremediation of pond water quality in aquaculture is one of the most important points to produce the safety aquatic products. Probiotics including Rhodopseudomonas palustris(Rho.Palustris) have attracted more attention in improving water quality and aquatic products safety.The attached bacteria have more metabolic action compared with free bacteria.So far,most applied probiotics are free and susceptible to the water flow and unease to work under the bottom of ponds.In addition, it is difficult for the probiotics to work for a long time with a stable style. PVA materials had been used to attach bacteria for better sediment. However,the second pollution to the environment was caused. Furthermore,the attachment process of preparation using PVA is complicated and costly.Thus,it is greatly important to seek a new and effective material in order to prepare probiotics-loaded particles and raise its degradation ability in pond water.In this paper,montmorillonite is used as loaded material.This paper investigates preparation conditions and mechanism of probiotics-loaded montmorillonite.Moreover, probiotics-loaded montmorillonite is applied in tilapia culture for improving the water quality and meat safety.The research provides new way and basis for biological restoration of water body and safety of aquatic products.The main results are as follows:(1) The most appropriate growth temperature and light intensity of probiotic,Rho.Palustris ZJ0716,are 30℃and 3000lx.The optimal initial pH value ranges from 7.0 to 7.5.Yeast extract added into the culture medium can increase growth rate and the optimum adding amount ranges from 0.2%to 0.4%.The strain ZJ0716 has a wide range of adaptability in salinity from 0.1%to 0.5%.(2) Preparation conditions of probiotics-loaded montmorillonite:The amount and percent of adsorbed microbe reach the maximum when the weight of montmorillonite is 0.5g in 10 mL liquid with a bacterial concentration of 2.55×10~9 cfu/mL.With 0.5g montmorillonite and l0.0mL Bacterium fluid,when the concentration is 15×10~8 cfu/mL,the percent of adsorption reach the maximum.With the increase of concentration,the amount of adsorbed microbe increase constantly.It shows that montmorillonite has a strong absorption for Rho.Palustris. With 0.5g montmorillonite and l0mL fluid of bacterial concentration of 2.55×10~9 cfu/mL,when the volume of Bacterium fluid is 30mL,the amount of adsorbed microbe reaches the maximum.But with the increase of volume,the percent of adsorption lessen constantly.With 30℃,pH 7 and low salinity conditions,montmorillonite has a maximum absorption rate for Rho.Palustris.(3) The indexes including pH,contents of ammonia nitrogen,nitrate, nitrite,COD and sulphide of water in the control groups were 7.58, 2.50mg/L,0.457mg/L,10.35mg/L,5.80mg/L and 0.011mg/L in the 30-day cultural period respectively.But in T-3,the same water quality indexes were 7.36,0.70 mg/L,0.197mg/L,5.22mg/L,3.11mg/L and 0.009 mg/L.Compared with the control group,all indexes of T-3 group decreased significantly(P＜0.05).The significant differences(P＜0.05) were also observed in the concentrations of ammonia nitrogen,nitrite and COD between T-3 and T-1 group.(4) The results of tilapia culture experiment indicated that DWG, RDR,condition factor,and gutting rate in the control group reach 0.52g/d, 126.39%,3.94%and 90.06%,respectively.The same indexes in T-3 groups with probiotics-loaded montmorillonite as additive are 0.66g/d, 162.80%,4.04%and 90.06%,respectively.Compared with the control group,DWG,RDR and gutting rate in T-3 group had significant increases. In the T-3 group fatness content of tilapia decrease from 3.62%to 2.71% and had more significant increase than the control group(P＜0.05).In T-3 groups,crude protein,moisture,ash,Fe and Zn content of tilapia muscle were improved by 82.17%,76.50%,5.49%,365.8mg/kg and 63.22mg/kg to 83.22%,78.25%,5.57%,386.2mg/kg and 65.71mg/kg,respectively. But there were no significant differences between T-3 and other groups (P＞0.05).In a word,probiotics-loaded montmorillonite integrates water purification of Rho.Palustris and adsorption characteristics of montmorillonite.The water quality was improved and the indexes including pH,ammonia nitrogen,nitrate,nitrite,COD and sulphide contents of culture water were decreased significantly.At the same time some growth of tilapia and meat quality characters were improved remarkably.The basic information would be provided for the application of probiotics-loaded montmorillonite in aquaculture according to our research.