북방전복, Haliotis discus hannai 에 대한 Bacillus amyloliquefaciens의 probiotic 효과

Abstract

Department of Aqualife Medicine, Chonnam National University, Yeosu 59629, KoreaIn comparison to the numbers of such studies of fish, few studies have been carried out on the immunity, physiology and ecology of abalone, while studies on abalone disease are also extremely rare. Moreover, mass mortality of cultured abalone due to pathogenic bacteria has not been reported in the southern coast of Korea. However, Vibrio-like bacteria have been isolated from dead abalone, which indicates that a review is required in order to determine the cause of abalone mortality. Use of an antimicrobial agent to minimize the damage caused by disease in abalone farms is common, but the therapeutic effects are insignificant. Demand for probiotics has increased, but research on the development of probiotics for use in abalone culture is very rare. Therefore, the present study isolated KC16-2 from fermented kimchi soup and investigated the characteristics of the isolate as a candidate probiotic bacterium in abalone. KC16-2 was identified as Bacillus amyloliquefaciens (B. amyloliquefaciens KC16-2) based on its biochemical properties and 16S rRNA gene sequence. B. amyloliquefaciens KC16-2 showed inhibitory effects against the growth of various vibrios in vitro, and kept the numbers constant until four days after inoculation in marine water at a temperature of 15～25℃, indicating the possible use of KC16-2 as a probiotic, except in the winter. The growth of KC16-2 was inhibited by bile salt, but the numbers increased over time suggesting the bacteria were still alive in the abalone's digestive tract. Abalone fed with a diet including KC16-2 for 12 weeks showed good growth, but showed no significant differences from the control group. However, the mortality of the abalone supplied the probiotic diet was reduced to half that of the control group in a challenge test with Vibrio tubiashii. Therefore, we suggest that B. amyloliquefaciens KC16-2 could be used as a probiotic bacterium for control of the mortality of abalone caused by opportunistic pathogenic vibrios.Key words: Abalone, Probiotics, Bacillus amyloliquefaciens, Vibrio tubiashii