Preparation of Water‐Soluble Yeast β ‐Glucan by Electron Beam Irradiation Combined With Hydrogen Peroxide Treatment and Evaluation of Its Effect on the Survival and Productivity of Penaeus monodon Shrimp in Intensive Farming Culture

Low molecular weight (Mw) β ‐glucans have been reported to have better growth promotion and immunostimulant activity in shrimps than that of native β ‐glucans. In this study, yeast water‐insoluble β ‐glucan was degraded by electron beam (EB) irradiation in the presence of hydrogen peroxide (H 2 O 2 ) to prepare water‐soluble and low Mw β ‐glucans. The Mw determination results showed that the Mw of irradiated samples was decreased by the increase in dose, pH, and H 2 O 2 concentration. The characteristic analysis of Fourier‐transform infrared spectra (FTIR) and X‐ray diffraction (XRD) patterns suggested that the EB irradiation did not cause any change in the basic structure of the irradiated β ‐glucan molecule, except for the reduction of Mw. For mass production of water‐soluble β ‐glucans with Mw ~15 kDa, the production rate using EB facility was calculated to be about 25.03 kg.h −1 , and this rate was about 2.9‐fold higher than the production rate using the gamma Co‐60 irradiator (8.74 kg.h −1 ). The results from field trial on Penaeus monodon shrimp indicated that EB‐irradiated β ‐glucan with an Mw of about 15.2 kDa not only significantly enhanced the production yield (26.3%) and survival rate (16.6%) but also reduced the feed conversion ratio (11.98%) of supplemented diet‐fed shrimps in the intensive farming trial compared with those of shrimps in the control trial without supplementation of β ‐glucan. Therefore, the water‐soluble β ‐glucan with Mw ~15.2 kDa prepared by EB irradiation in the presence of H 2 O 2 is a highly promising natural feed additive for improving the survival rate and production yield of shrimps in intensive farming culture.