[Cloning of beta-amylase gene from B. substitute and its expression in E. coli]

The gene coding for beta-amylase with raw starch-digestion ability was isolated from B. substitute R2 which was selected in this lab. The procedure used in this screening was developed in this work by the method named nutrition-restriction. The DNA fragment containing the beta-amylase gene was 5.25 kb in length. There was no difference in enzymological properties between the beta-amylase produced by the gene-donor strain and the expression product of E. coli. The yield of the cloned beta-amylase was over 500 IU/ml in our laboratory culture condition, the RDA value was 57%, and all of this enzyme were found to be secreted into medium.