Effects of extracellular products of Bacillus licheniformis De on the amylase activity of Litopenaeus vannamei in vitro

The interaction between extracellular products(ECP) of Bacillus licheniformis strain De and amylase of white shrimp(Litopenaeus vannamei) was studied in vitro.The ECP were collected by semiperable membrane method,and the digestive enzyme of white shrimp hepatopanceas and intestine were collected by homogenate and centrifugation.The effects of ECP on amylase activity of white shrimp were investigated at different temperature,pH and ECP concentration.There were 5 test groups(A,B,C,D,E) in this experiment,the digestive enzyme of group A was ECP,groups B and C were hepatopanceas and intestinal digestive enzyme of shrimp supplemented with ECP,groups D and E were control groups of B and C,which enzyme without ECP.The results indicated that amylase activity of enzyme of test groups B and C(ECP were added) were significantly higher than(p0.05) that of the control groups D and E at 20～40℃,which temperature was much lower than the optimum temperature for amylase activity of ECP(60~90℃),comparatively,the hepatopanceas and intestinal amylase activity of white shrimp increased 25.9% and 19.3%,respectively.The amylase activity of test groups B and C were significantly higher(p0.05) than that of control groups at the optimum pH(5~6),under the optimum pH amylase activity of hepatopanceas and intestine increased 33.3% and 122.2% compared with that of control groups,but the optimum pH for the amylase of group A was 6~9,it was higher than the optimum pH(5~6).Moreover,the results also showed that the amylase activity of test groups(ECP were added) decreased with increasing of the quantity of ECP,which implied ECP of Bacillus licheniformis,maybe,was a kind of inhibitor for white shrimp endogenetic amylase in the certain condition.In conclusion,ECP of Bacillus licheniformis could improve amylase activities of white shrimp in vitro in a certain extent,if ECP amylase exceeded 0.02U/mg protein the activity of white shrimp endogenetic amylase would be decreased.