High Soluble Expression of d-Amino Acid Oxidase in Escherichia coli Regulated by a Native Promoter

摘要

To express high-active soluble d-amino acid oxidase (DAAO), a constitutive plasmid that is regulated by a native hydantoinase promoter (PHase), was constructed. A d-amino acid oxidase gene (dao) was ligated with the PHase and cloned into pGEMKT to constitutively express protein of DAAO without the use of any inducer such as isopropyl β-d-1-thiogalactopyranoside which is poisonous to the cells and environment. The ribosome binding site region, host strain, and fermentation conditions were optimized to increase the expression level. When cultivated in a 5-m3 fermenter, the enzyme activity of JM105/pGEMKT-R-DAAO grown at 37 °C was found to be 32 U/mL and increase 16-fold over cells of BL21(DE3)/pET-DAAO grown at 28 °C. These results indicate the success of our approaches to overproducing DAAO in soluble form in Escherichia coli.