Constitutive overexpression of the endoxylanase gene in Bacillus subtilis

Abstract

A strong constitutive P(JH) promoter from Bacillus was applied to overexpress the endoxylanase gene in B. subtilis. The expression plasmid, pJHKJ4, was designed to contain the P(JH) promoter and endoxylanase promoter (P(B)), and introduced into B. subtilis DB104. Through batch fermentation of the transformant cell on a maltose medium, endoxylanase was produced in a growth-associated manner as the predominant protein. The total activity reached about 600 unit/ml at the end of the cultivation, which corresponded to 698 mg endoxylanase protein/l with a specific activity of 860 unit/mg protein. It was also found that the segregational plasmid instability was less than 30% and most of the endoxylanase activity was detected in the culture medium. This result suggests that the secretory production of endoxylanase can be significantly enhanced with the use of the P(JH) promoter and high-cell density culture techniques, quantitatively as well as qualitatively.