Enhancing extracellular protein production in by deleting the d-alanyl-d-alanine carboxypeptidase gene .

d-Alanyl-d-alanine carboxypeptidase DacC is important for synthesis and stabilization of the peptidoglycan layer of . In this work, of . BL21 (DE3) was successfully deleted, and the effects of this deletion on extracellular protein production in . were investigated. The extracellular activities and fluorescence value of recombinant amylase, green fluorescent protein, and α-galactosidase of the deletion mutants were increased by 82.3, 29.1, and 37.7%, respectively, compared with that of control cells. The outer membrane permeability and intracellular soluble peptidoglycan accumulation of deletion mutant were also enhanced compared with those of control cells, respectively. Based on fluorescence-assisted cell sorting analyses, we found that the morphology of the deletion mutant cells was altered compared with that of control cells. Local transparent bulges in the poles of the . mutant with deletion of the gene were found by transmission electron microscopy analysis. These bulges in the poles could explain the improvement in the production of extracellular protein by the mutant with deletion of the gene. These findings provide important insights into the extracellular production of proteins using . as microbial cell factories.