Abstract: In the experiment, a traditional method to enrich, separate and purify microorganisms was used in the digestive tract of Ligia exotica, and a strain with strong enzyme production ability was obtained and was named HZL-3 which was preliminarily determined as Bacillus coagulans by using molecular biological method. Contents of protease and amylase produced by HZL-3 was measured by ELISA and the effects of temperature, pH, culture time, inoculation amount and other factors on the amount of enzyme production were studied. The results showed that HZL-3 was able to produce protease and amylase; when cultured for 16 h at 36 ℃, pH 7.5, and 6% inoculation amount, protease activity was maximal; and amylase activity was the highest at 36 ℃, pH 6.0, when inoculation amount was 4%, and cultured for 10 h. This study aims to reveal the potential applications of microorganisms in the digestive tract of Ligia exotica as probiotics in aquaculture.

Key words: Ligia exotica, Bacillus coagulans, isolation and identification, protease, amylase