Dietary Administration Effects of Exopolysaccharide Produced by Bacillus tequilensis PS21 Using Riceberry Broken Rice, and Soybean Meal on Growth Performance, Immunity, and Resistance to Streptococcus agalactiae of Nile tilapia (Oreochromis niloticus)

Abstract

Overuse of antibiotics in aquaculture has generated bacterial resistance and altered the ecology. Aquacultural disease control requires an environmentally sustainable approach. Bacterial exopolysaccharides (EPSs) as bioimmunostimulants have not been extensively explored in aquaculture. This study investigated EPS produced from 5% w/v riceberry broken rice as a carbon source and 1% w/v soybean meal as a nitrogen source by Bacillus tequilensis PS21 from milk kefir grain for its immunomodulatory, antioxidant activities and resistance to pathogenic Streptococcus agalactiae in Nile tilapia (Oreochromis niloticus). The FTIR spectrum of EPS confirmed the characteristic bonds of polysaccharides, while the HPLC chromatogram of EPS displayed only the glucose monomer subunit, indicating its homopolysaccharide feature. This EPS (20 mg/mL) exhibited DPPH scavenging activity of 65.50 ± 0.31%, an FRAP value of 2.07 ± 0.04 mg FeSO4/g DW, and antimicrobial activity (14.17 ± 0.76 mm inhibition zone diameter) against S. agalactiae EW1 using the agar disc diffusion method. Five groups of Nile tilapia were fed diets (T1 (Control) = 0.0, T2 = 0.1, T3 = 0.2, T4 = 1.0, and T5 = 2.0 g EPS/kg diet) for 90 days. Results showed that EPS did not affect growth performances or body composition, but EPS (T4 + T5) significantly stimulated neutrophil levels and serum lysozyme activity. EPS (T5) significantly induced myeloperoxidase activity, catalase activity, and liver superoxide dismutase activity. EPS (T5) also significantly increased the survival of fish at 80.00 ± 5.77% at 14 days post-challenge with S. agalactiae EW1 compared to the control (T1) at 53.33 ± 10.00%. This study presents an efficient method for utilizing agro-industrial biowaste as a prospective source of value-added EPS via a microbial factory to produce a bio-circular green economy model that preserves a healthy environment while also promoting sustainable aquaculture.

Development of Biological Coating from Novel Halophilic Exopolysaccharide Exerting Shelf-Life-Prolonging and Biocontrol Actions for Post-Harvest Applications

“…The optimum EPS production of 19.47 ± 1.45 g/L was reported after physicochemical optimization, which was better than the formerly reported EPS quantity of B. tequilensis strains. Sutthi [40] reported that B. tequilensis PS21 strain produced 15 g/L EPS in optimized conditions. However, [39] enhanced the EPS production up to 24 g/L by culturing the B. tequilensis PS21 in riceberry broken rice, and soybean meal broth.…”

Organic acids mitigate Streptococcus agalactiae virulence in Tilapia fish gut primary cells and in a gut infection model

“…Over the past thirty years, Nile Tilapia ( Oreochromis niloticus ) has ascended to the forefront of freshwater aquaculture, reaching a global market valuation of US $7.9 billion as of 2020, being cultivated in more than 120 of different nations [ 1 , 2 ]. The cultivation of Nile Tilapia has transitioned from predominantly extensive farming practices to the proliferation of intensive, commercial aquaculture operations due to a rapid reproductive rates and pronounced solvability [ 3 ]. This shift has positioned Nile Tilapia farming as one of global aquaculture’s most rapidly expanding sectors [ 4 ].…”

“…The volume of Tilapia production witnessed a substantial increase, expanding from 1.0 million tonnes in 2001 to 3.6 million tonnes by 2014 and 4.6 million tonnes in 2019 [ 2 , 6 ]. Currently, Tilapia contributes approximately ≈ 4.8 million metric tons to worldwide food security, serving as a comparatively affordable protein source with premium meat quality [ 3 , 4 ]. In 2017, Tilapia emerged as a significant agricultural product for Indonesia, which accounted for 18.43% of the total global output of 6,510,700 tons [ 5 ].…”