Bioencapsulation and application of Lactobacillus plantarum isolated from catfish gut as an antimicrobial agent and additive in fish feed pellets

Lactobacillus plantarum was isolated from fresh water catfish collected from a local market. The probiotic-like characteristics of the bacteria, and its antibacterial effects against common food-borne and fish pathogens, were investigated by growing it in different diverse conditions (varying osmolarity, bile salt, acid and alkaline conditions, and temperature). The L. plantarum was encapsulated in a mixture of alginate and fish gelatin protein at different concentrations to enhance its protection during incorporation into fish feed pellets. The significance of encapsulation was proven by exposing the encapsulated L. plantarum to harsh conditions in comparison to un-encapsulated cells as a control. The results suggest that 2 % alginate and 13 % gelatin coating material had optimal textural properties, with a hardness of 1.436 N, high viscosity of 20.23 cP and highest encapsulation efficiency with 8.45 log colony forming units (CFU). The bacteria showed antagonistic effects against the fish pathogen Streptococcus agalactiae, and other common pathogens such as Salmonella typhimurium, Escherichia coli and Klebsiella pneumoniae. Encapsulated L. plantarum was found to tolerate pH 2 and pH 8 more efficiently compared to un-encapsulated cells, and encapsulated cells survived 6 log CFU from an initial 8.23 log CFU count at low pH 2 after a 90-min incubation and showed resistance to 50 degrees C for 1 h. Thus, the isolated L. plantarum was found to have potential to be used successfully in fish feed and other similar applications.