Study on probiotic potential of Bacillus species isolated from the intestine of farmed rainbow trout, Oncorhynchus mykiss

The gastrointestinal tract of fishes is a complex ecosystem occupied by a large number of microorganisms, some of them could have potentially-valuable features. This research was conducted to study Bacillus species in the intestine of farmed rainbow trout to examine their probiotic properties, and to provide a new source of probiotics. A total of 23 farmed rainbow trout were sampled and their intestine samples were cultured. Following the morphological assay and biochemical analysis, isolated Bacilli were amplified by polymerase chain reaction and universal primers 27f and 1492r. Bacillus subtilis and B. amyloliquefaciens were isolated from 5 and 3 samples, respectively. Bacillus tequilensis, B. cereus and B. licheniformis were isolated from 1 sample. Probiotic properties of B. subtilis strain MSM 24, B. amyloliquefaciens strain TMM 25 and B. licheniformis strain MR 78 were confirmed. Since probiotic bacteria cause no foodborne diseases, their existence in farmed trout intestines, and their penetration into the fish tissues do not pose any risk to consumers’ health.