Food-grade expression of an iron-containing acid urease in Bacillus subtilis.

Enzymatic degradation of urea, the precursor of carcinogenic compound ethylcarbamate in rice wine, is always attractive. In the present study, we achieved high efficient production of Bacillus paralicheniformis iron-containing urease (Bp_Urease) in B. subtilis with the food-grade expression system. After reassembly of the urease gene cluster with inserting ribosome binding site (RBS), the production was increased from 38 U/L to 187 U/L. After altering the position of ureC and co-expressing the iron transporter encoding gene ureH, the activity was further increased to 1307 U/L. Eventually, the urease production was improved to 21,964 U/L in 3-L fermentor, which is the highest reported value to date. Food-grade production of the iron-containing urease would be favorable to the practical applications in food industries.