The present study investigated the effect of polysaccharide gel (PG) extracted from the rind of durian fruit which is encapsulated with Bacillus subtilis as a feed and co-inoculation with Artemia nauplii in the induction of immune response in Danio rerio after Vibrio immersion challenge (5 days). The total RBC count, lysozyme activity test, weight, and length analysis revealed that the zebra fishes fed with the PG encapsulated probiotics had more immune induction activity, survival, and growth than the non-encapsulated groups. When the expression of the immune-related genes was measured, the studies revealed the significant upregulation (P < 0 .05) of interleukin 1 beta (Il1b), lysozyme (lyz), tumor necrosis factor-alpha (TNF-α), superoxide dismutase (SOD) genes in fish fed with PG encapsulated probiotics with A. nauplii showed an immense effect on the induction of immune response compared to other feeds.

Hydroxyapatite [Ca 10 (PO4) 6 (OH) 2 ] (HAp) has been regarded as a bone mineral, which acts as a grafting material due to its similar chemical composition with natural bones. HAp is thermodynamically stable at physiological pH and actively takes part in bone bonding. This property led has lead to HAp being widely used for rapid bone repair. HAp is derived from natural bio wastes such as fish scale which is the most definite standard source of both organic and inorganic constituents like collagen and hydroxyapatite. Titanium biomimetic method with the immersion of Stimulated Body Fluid solution were also used widely used for the precipitation of hydroxyapatite synthetically. Hence scales of Sardinella longiceps and titanium are chosen to be the essential source for the isolation of hydroxyapatite (HAp) in this current study. X-Ray Diffraction, Fourier-Transform Infrared spectrometry, Scanning Electron Microscopy confirms the phase, structural integrity and size of isolated HAp. Biocompatibility and calcium deposit assay with osteoblast cell line demonstrates the non-toxicity and efficiency of calcium deposits by HAp scales rather than synthetically derived Titanium mediated HAp. Hydroxyapatite can be doped with bactericidal silver nitrate and a biopolymer, bioadsorbable chitosan for the controlled release, targeted delivery, and corrosion resistance.

In this study, bacterial strains were isolated from curd and evaluated its bactericidal potential against two aquatic pathogens Salmonella sp and Vibrio sp isolated from marine fish, Parastromateus niger and squid, Loligo duvauceli. Based on the antimicrobial activity, potential strain was selected and identified as Bacillus sp. Further, bacteriocin was partially purified from the Bacillus sp by ammonium sulphate precipitation and dialysis. The molecular weight of the partially purified bacteriocin was estimated by SDS-PAGE. To understand the biopreservative ability of the purified bacteriocin, tissues of Salmonella and Vibrio-infected fish, Parastromateus niger and Loligo duvauceli were treated with bacteriocin for 30 days at different storage conditions (-4°C and -20°C) and the microbial load was counted at 5, 10, 15, 20, 25 and 30 days. Results showed that bacteriocin significantly reduced the total bacterial count at both storage temperatures in a time dependent manner. This study proved the efficiency of bactericidal and biopreservative activity of bacteriocin isolated from Bacillus subtilis (KY808492).