Probiotic potential of Lactobacillus sp. strains capable of phytate breakdown isolated from dairy products for using in rainbow trout (Oncorhynchus mykiss Walbaum, 1792) diet

This research investigated the feasibility of using three strains Lactobacillus sp. viz. AM11, AM13, and AM14 previously isolated from dairy products to be used as probiotics in fish diet for phytase production. The bacteria grown in oxygenated media, bile salt, acid and supernatant of digestive tract  were examined for their antibiotic resistance and non-pathogenicity for using in fish feed. Results indicated that the isolates might be attractive candidates as probiotic strains in rainbow trout. All strains were capable of growth and produced phytase in a pH range from 3.0 to 8.0. The isolated strains were also resistant in bile salts and supernatant of digestive tract. No mortality has been observed in the fish injected by bacterial strains. No bacterial growth has observed in the liver, kidney and spleen media after 24 h. Therefore, the examined Lactobacillus strains were non-pathogenic. Due to the low resistance of these strains to tetracycline (antibiotic), it is suggested to avoid using tetracycline in rainbow trout farms when the bacterial strains are used as probiotic. According to the results, the three isolated resistant strains can be employed as probiotics in fish feed.