Survival and Growth Promoting Effects of Bacillus subtilis on Macrobrachium rosenbergii, and Validation of Gut Microflora

This study emphasized the survival and growth of the commercially important freshwater prawn, Macrobrachium rosenbergii post-larvae on formulated diets supplemented with a probiotic bacterium, Bacillus subtilis at five different serially diluted concentrations (10-1, 10-3, 10-5, 10-7 and 10-9). After 90 days of feeding, 10-7 (CFU, 2.76×10-7) concentration produced the best results in increased survival rate, weight gain, basic biochemical constituents (total protein, amino acid, carbohydrate and lipid) and activities of digestive enzymes (protease, amylase and lipase) when compared with control diet prepared without B. subtilis. This was due to maintenance of good intestinal health, because of B. subtilissupplementation. The presence of B. subtilis, Bacillus cereus, Lactobacillus delbrueckii(subsp. bulgaricus), Lactobacillus casei, Lactobacillus rhamnosus and Streptococcus pyogenes have been identified in the gut of M. rosenbergii fed with B. subtilis supplemented diet, through 16S r-RNA gene sequencing which was authenticated with NCBI GenBank. The pathogenic bacteria such as Escherichia coli, Klebsiella spp., and Staphylococcus spp.,present in the control prawns as per our previous study (Manjula et al., 2018), were competitively excluded by the experimental prawnsfed with B. subtilis supplemented diet in the present study. Therefore, B. subtilis is recommended for sustainable production of M. rosenbergiiseed.