Studies on screening and breeding of alkaline pullulanase producing bacterium and regulation of nutrition

Bacillus sp. SX 12,a strain producing alkaline pullulanase,was isolated from baby food.The optimal condition for preparating of the protoplast and its regenerating were studied.Protoplast of Bacillus sp. SX 12 were induced by ultraviolet ray.One High producing strain (SX 12C 67 ) were obtained from process of screening.The activity of alkaline pullulanase in strain SX 12C 67 increased from 2.42 U/mL in strain SX 12 to 6.87 U/mL,About 1.8 times to which in strain SX 12.The fermentation medium and culture condition of the strain were investigated,the optimum medium for fermentation is that Soluble Starch 3%,pepton 1.0%,Yeast extract 0.5%,K 2HPO 4 0.2%,MgSO 4.7H 2O 0.05%,MnCl 2 0.0001%.The optimum temperature is 40℃,The optimum pH is 9.5,The optimum temperature for enzyme is 55℃,The optimum pH is 10.0-10.5.It shows a high stability during pH 6.0-11.0 at 55℃.The activity of alkaline pullulanase could be promoted by Ca 2+ ?Mn 2+ ?Mg 2+ and inhibited by Zn 2+ ?Hg 2+ .