Study On Improving Limit Dextrinase Activity In The Saccharifying Course

Investigating the amounts of free,bound,and total limit dextrinase in malted barley from Qingdao Beer Limited Company were studied.It is found that different malts have different kinds of amylases and also have different saccharifying products components.Experimental design for two enzyme(alpha-amylase,beta-amylase) starch mashes concludes that for given level of fermentable sugar,decreasing the activity of one amylase enzyme could be compensated for by increasing the activity of the other.Experimental design for three enzyme(alpha- amylase,beta-amylase, limit dextrinase) starch mashes concludes that addition of limit dextrinase to the mashes resulted in a substantial increase in levels of fermentable sugars.Amounts of proteinase,sulfhydryl proteinase in malted barley and malted barley adding metal ions were studied.The secretion rule of limit dextrinase during the germinating and kilning course were studied,combing with two hypotheses for the release of free limit dextrinase from a bound form,we carried out research on the the enzymatic properties of Limit Dextrinase in vitro.We conclude that the producing and reducing cycle of proteinase is short and sulfhydryl proteinase has good producing and reducing rate.During early stage of germinating free limit dextrinase is in the majority,and during later stage of germinating bound limit dextrinase is in the majority,even increases to 70%of total limit dextrinase for 9d.Free limit dextrinase's proportion in total limit dextrinase after kilning decrease to 20.9%while in malted barley for 5d 32.8%;bound limit dextrinase's proportion in total limit dextrinase after kilning increase to 78.9%while in malted barley for 5d 67.2%.Heat resistance of bound limit dextrinase is stronger than free limit dextrinase's. Limit dextrinase is not a sulfhydryl enzyme.L-CYS significantly increased the activity of limit dextrinase in extracts,because L-CYS activated sulfhydryl enzyme, and the bound limit dextrinase release is mediated by sulfhydryl.These results strongly suggest that the possibility of proteolytic enzymes regulation to improve Limit Dextrinase activity in the saccharifying course.The separation and purification techniques of Limit Dextrinase inhibitor from a crude barley extract with sodium acetate buffer were explored in the present work to obtain high pure Limit Dextrinase inhibitor.The optimized purification process includes the following steps:80℃heat treatment of the grist extract,CM52 cellulose ion exchange chromatography and gel filtration chromatography.The activity of Limit Dextrinase inhibitor was measured by Limit Dextrinase activity reduction inhibited by Limit Dextrinase inhibitor.The purification factor and activity recovery of Limit Dextrinase inhibitor was 6.97 and 57.9%,respectively.