Isolation of Aeromonas sobria JC18 from milkfish (Chanos chanos) intestine with proteolytic and cellulolytic activities for fish probiotic

Abstract

Attention on the probiotic application for the improvement of fish resident intestinal microbiota has risen in the last decades. It is demonstrated that probiotics may function not only by direct inhibition of pathogenic bacteria or manipulation of enzymatic digestion of feed but also by modulation of immunity in fish. In the present study, we aimed to isolate the autochthonous microbiota of marine fish intestines as probiotic candidates based on cellulolytic and proteolytic activity. Bacteria were isolated and purified on a cellulose agar with 24h of incubation. A total of 18 bacterial strains were purified and stored in-80°C. Phenotypic screening based on the antibiotic resistance, antagonistic activity against pathogenic bacteria, resistance to an acidic environment, and ability of colonization in fish intestine found a selected strain, namely JC18. Infection test, molecular and phenotypic characterizations revealed that the JC18 isolate was a non-pathogenic Aeromonas sobria. It is hence revealed that the milkfish intestine is a potent source of proteolytic bacteria for fish probiotic screening.