Effects of Bacillus subtilis on immunization indicators,growth performance and culture water quality of Portunus trituberculatus

ObjectiveEffect of Bacillus subtilis on feeding performance of Portunus trituberculatus were studied to pro-vide reference for healthy culture of P. trituberculatus and promoting application of probiotics in crab culture.MethodWith P. trituberculatus being research target,experiment group(EG,adding 2×1010 CFU/g B. subtilis)and control group(CK,adding no probiotics). The experiment cycle was 28 d,during the period,growth indexes and water quality factors were measured at regular intervals. After the experiment,activities of alkaline phosphatase(AKP),acid phosphatase(ACP),peroxidase(POD), total superoxide dismutase(T-SOD)and lysozyme(LZM)in hemolymph of P. trituberculatus.ResultB. subtilis could signifi-cantly improve AKP activity in hemolymph of P. trituberculatus(P<0.05,the same below). AKP activity gradually increased as culture time extended;ACP and POD activities gradually increased and reached the peaks on day 21(6.47U/100ml and 45.93U/ml),which were significantly higher than CK. The use of B. subtilis had no significant effects on T-SOD activity(P>0.05), but it had obvious influence on LZM content. LZM content reached the maximum on day 21(3.81 μg/mL),and then it remained at a stable level. B. subtilis did not obviously promote the growth of P. trituberculatus,but greatly improve the livability. Until the end of experiment,livability of P. trituberculatus in EG increased by 17.78%compared with CG. In addition,B. subtilis could veffectively reduce the content of NH3-N and NO2-N in cultured water,however,the effects was decreased after day 21.concultionBacillus subtilis can significantly improve immunization-related enzyme activities,improve livability and re-ducing NH3-N and NO2-N contents in culture water to purify water quality.