Optimization Of Feed Protease Stability And Enzyme Activity Analysis

Protease,a kind of proteolytic enzyme,is one of the most important enzyme products.Protease has been widely used in the life.However,due to the external conditions(high temperature and high humidity),the protease has some problems in storage stability during transportation,such as flatulence in the long-distance transport,a sharp decline in enzyme activity under high temperature conditions,enzyme activity decreasing and turbidity with a long time storage,and so on.In our study,it is desirable to increase the stability of the liquid protease and to improve the appearance of the liquid protease by adding preservatives,surfactants,and antioxidants.(1)This article compares the two detection method of protease: national standard Forint method and the UV method.The results confirmed that the Forint method is suitable for protease-only enzyme preparation and protease-containing complex enzyme preparation,while UV method for protease-only enzyme preparation.The rest of this experiment used UV to detect protease activity.(2)In this experiment,the optimum effect pH of acid protease produced by Aspergillus niger and Aspergillus ussorum was 2.5,the optimal temperture was 55?;the optimum effect pH of neutral protease produced by Bacillus subtilis code-named "1.398" was 7.5 and the optimal temperture was 50?.The acid protease derived from Aspergillus niger had the best temperature resistance.(3)The optimum pH of liquid acid protease from Aspergillus niger and Aspergillus usamii were about 4.0~5.0.The suitable protective agents for screening were glycerol and sodium chloride.The single glycerol addition was 15%~20% and the addition of sodium chloride was 4%.The appropriate protective agent of acid protease from Aspergillus usamii has yet to be explored.The final test result showed that the most suitable protective agent of neutral protease produced by strain code-named 1.398 Bacillus subtilis was glycerol,and the addition amount was 20%.(4)The effects of three ions,sodium,phoshobiun,and calcium,on the activity of acid protease and neutral protease were mainly studied in this experiment.The results were:Phosphonium ion presented as the form of monocalcium phosphate,and it had no effect on neutral protease activity when the concentration of phosphonium was 0.275%,while an inhibition when the concentration was 2.75%.Sodium presented had an inhibition on neutral protease activity when the concentrations of sodium were 0.55% and 5.5%;Calcium ion presented had an inhibition on neutral protease activity when the concentrations of calcium salts were 0.75% and 7.5%.There was no activation on the acid protease for the three ions,neither inhibition.