Enhanced secretion of heterologous cyclodextrin glycosyltransferase by a mutant of Bacillus licheniformis defective in the D-alanylation of teichoic acids

AIMS: To examine whether inactivation of the dlt operon and increased charge density of the wall enhances secretion of heterologous proteins in industrial strains of Bacillus licheniformis. METHODS AND RESULTS: The dltA gene of B. licheniformis was cloned, sequenced and mutated by inserting a chloramphenicol acetyl transferase (cat) gene cassette. The mutation facilitated growth in the late exponential growth phase, increased endogenous autolysis and decreased resistance to a cationic peptide, polylysine. It was observed that dltA mutation increased the production of cyclodextrin glycosyltransferase (CGTase) by 1.5- to sevenfold depending on the growth phase, but decreased the production of penicillinase by twofold. CONCLUSIONS AND SIGNIFICANCE: The results suggest that the d-alanylation of teichoic acids is an element that can be used to improve the production of some secretory proteins in industrial applications based on this important industrial microorganism.