Synergic degradation of yeast β-glucan with a potential of immunostimulant and growth promotor for tiger shrimp

The synergic effect using gamma-irradiatio in combination with hydrogen peroxide was applied for preparation of water-soluble and low molecular weight (Mw) beta-glucan from yeast water-insoluble beta-glucans. The structural characterization by gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) suggested that the gamma-irradiation did not cause any change in basic structure of beta-glucans, except for the reduction in degree of polymerization. The suitable degradation conditions were determined at 10% beta-glucans in pH similar to 9% and 1% hydrogen peroxide. The water-soluble oligo beta-glucan with Mw similar to 15 kDa showed a significantly effect on the increase of body weight and survival rate of Penaeus monodon shrimps challenged with Vibrio parahaemolyticus and White spot syndrome virus (WSSV). The oral administration of 15 kDa-oligo beta-glucan with a daily dose of 1000 ppm strongly stimulated immune factors in tested shrimps such as phagocytosis activity (PA), phenoloxidase (PO) and superoxide dismutase (SOD). Furthermore, dietary of 1000 ppm 15 kDa-oligo beta-glucan also significantly up-regulated the gene expressions of lipopolysaccharide and beta-1,3-glucan-binding protein (LGLP) and prophenoloxidase (proPO). The relative percent of survivals (RPS) of shrimps fed with 1000 ppm 15 kDa-oligo beta-glucan were 56.2% and 38.1% post the challenge with V. parahaemolyticus and WSSV, respectively. These results demonstrated that the water-soluble oligo beta-glucan with Mw similar to 15 kDa prepared by synergic degradation method showed a very promising potential for application as a natural growth promotor and immunostimulant in shrimp culture.

Automated summary

The synergic effect of gamma-irradiation and hydrogen peroxide was used to prepare water-soluble and low molecular weight beta-glucan, which showed significant effects on body weight and survival rate of Penaeus monodon shrimps challenged with Vibrio parahaemolyticus and White spot syndrome virus. The 15 kDa-oligo beta-glucan also stimulated immune factors and gene expressions, leading to increased survival rates of shrimps post infection. These results indicate a promising potential for the application of the water-soluble oligo beta-glucan in shrimp culture as a natural growth promoter and immunostimulant.