Effects of encapsulated Bacillus sp. D2.2 on gut bacterial composition and immune system in brown-marbled grouper Epinephelus fuscoguttatus

Abstract

In the aquaculture industry, the application of probiotics is well known widely used to control disease, improve water quality and reduce demands for the use of antibiotics or disinfectants. However, some local gut bacteria can bind to harmful bacterial component. For better efficacy of probiotics in the digestive tract of carnivorous fish, encapsulation can be a simple, harmless, and improved method to maintain the microflora of the digestive tract thereby enhancing the immune system of fish. This study was conducted to investigate the effects of encapsulated probiotic Bacillus sp. D2.2.on gut bacterial communities and immune system in brown-marbled grouper Epinephelus fuscoguttatus. One hundred fish weighing about 40 g were divided randomly into five groups including negative control and positive control groups which were fed by a commercial diet only and a diet containing probiotic respectively, the third to fifth groups were fed by 1, 2, and 3 g/kg encapsulated probiotics dose of feed respectively. The results showed that encapsulated probiotic increase viability of probiotic bacteria and also affect the abundance of lactic acid bacteria. Immune response of the brown-marbled grouper also increased significantly after the application of encapsulated probiotics.