Molecular Identification of Amylolytic Bacteria Isolated from Digestive Tract of Milkfish (Chanos chanos Forskal) based on 16S rRNA Gene Sequences

Probiotic bacteria play an important role in fish growth and health in aquaculture, especially in fish rearing in inland waters. This study aimed to identify bacteria from the digestive tract of milkfish (Chanos chanos Forskal) and investigate their potential as probiotic candidates. Bacteria were isolated from the digestive tract of milkfish and identified using PCR technique and 16S rRNA gene sequencing. The probiotic potency was determined using amylolytic assay, synergistic activity, hemolytic activity, and antagonistic activity. The results showed that there were several types of bacteria found in the digestive tract of milkfish. One of these bacteria could produce an amylase enzyme with an amylolytic index of 5.16, identified as Bacillus paramycoides. This bacteria also synergized with other bacteria and did not have hemolytic activity on blood agar media. The results of the antagonistic test based on the well-diffused method against Aeromonas hydrophila showed that B. paramycoides did not produce an inhibition zone around the bacterial wells. The molecular identification found that the bacterial species was B. paramycoides B2.1. These results suggested that Bacillus paramycoides B2.1, which is found in the digestive tract of milkfish, can be used as a probiotic candidate for fish feed indicated by several probiotic tests that have been carried out.