Evaluation of cholesterol lowering property and antibacterial activity of two potential lactic acid bacteria isolated from the intestine of snakehead fish (Channa argus)

The use of lactic acid bacteria (LAB) is a strategy employed to improve aquatic animal health status and to prevent aquaculture diseases. In the present study, two potential LAB were isolated from the intestines of Channa argus (C. argus) towards the assessment of their probiotic potential. Based on the preliminary screening on 178 isolates obtained from the intestines of C. argus, only ten LAB isolates were selected by using LAB selective media (MRS-CHOL medium) for their high cholesterol removal capacity. Five potential LAB isolates (W1, W24, C11, L1 and L19) were all had high inhibitory effects on a variety of aquatic pathogenic bacteria and all able to survive in acidic and alkaline conditions, higher tolerance to bile salt, high surface hydrophobicity, high auto-aggregation property and they were found to tolerate in in pepsin and trypsin solution environmental condition. Based on the presently observed biological characteristics, it is concluded that the W24 and L19 isolates were more effective than the W1, C11 and L1 isolates. Two potential LAB strains, W24 and L19 were identified as Enterococcus faecalis (Genbank: MT102745.1) and Lactococcus lactis (Genbank: MT102746.1) respectively by 16S rRNA sequencing. The identification of physiological and biochemical properties results showed that the W24 and L19 isolates could ferment a variety of sugars, which was in line with the characteristics of LAB. The two potential LAB isolates (W24 and L19) were susceptible to the vast majorityantibiotics and were all respectively exhibited γ-haemolysis (i.e. no haemolysis) activity. The biosafety assay confirmed that the two potential LAB isolates were not pathogenic to the host fish. Therefore, the E. faecalis W24 and L. lactis L19 may be a promising candidate for the development of functional micro-ecological feed. This study has provided insight into how optimal LAB should be isolated and screened from the intestines of C. argus.