Use of few-layer Zn2In2S5 nanosheets as an environmentally friendly visible-light photocatalyst for directly transforming methanol to ethylene glycol with high selectivity.

is one of the most widely used host microorganisms for recombinant protein expression and metabolic engineering, but it cannot efficiently secrete recombinant proteins to extracellular space. Here, extracellular protein secretion was enhanced in by deleting two d,d-carboxypeptidase genes ( and , single and double deletions) to perturb the cell wall peptidoglycan network. Deletion of and enhanced the accumulation of intracellular soluble peptidoglycan in and affected cell morphology, resulting in a more irregular cell shape and the appearance of transparent bulges. Deletion of and appears to disrupt the normal rigid structure, presumably due to perturbation and destruction of the cell wall peptidoglycan network. The extracellular green fluorescent protein (GFP) fluorescence intensity of deletion mutants was increased by >2.0-fold compared with that of control cells, and that of the double deletion mutant was increased by 2.7-fold. Extracellular recombinant fibroblast growth factor receptor 2 (FGFR2) and collagen E4 secretion in deletion mutants was also enhanced compared with that in the control cells. Additionally, the extracellular recombinant amylase activity of single-deletion mutants BL21 Δ pETDuet- and BL21 Δ pETDuet- was increased 2.5- and 3.1-fold, respectively. The extracellular distribution of α-galactosidase by deletion mutants was also increased by >2.0-fold. Deletion of and increased outer membrane permeability, which could explain the enhanced extracellular protein secretion. Cell surface structure stabilization is important for extracellular secretion of proteins in As the main constituent of the cell wall, peptidoglycan contributes to cell structure robustness and stability. Here, we perturbed the peptidoglycan network by deleting and genes encoding d,d-carboxypeptidase enzymes to improve extracellular protein secretion. This new strategy could enhance the capacity of as a microbial cell factory for extracellular secretion of proteins and chemicals.

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