Improved Membrane Permeability Via Hypervesiculation for in Situ Recovery of Lycopene in Escherichia Coli.

Lycopene biosynthesis is frequently hampered by downstreamprocessinghugely due to its inability to be secreted out from the producingchassis. Engineering cell factories can resolve this issue by secretingthis hydrophobic compound. A highly permeable E. coli strain was developed for a better release rate of lycopene. Specifically,the heterologous mevalonate pathway and crtEBI genesfrom Corynebacterium glutamicum wereoverexpressed in Escherichia coli BL21(DE3) for lycopene synthesis. To ensure in situ lycopeneproduction, murein lipoprotein, lipoprotein NlpI, inner membrane permeaseprotein, and membrane-anchored protein in TolA-TolQ-TolR were deletedfor improved membrane permeability. The final strain, LYC-8, produced438.44 & PLUSMN; 8.11 and 136.94 & PLUSMN; 1.94 mg/L of extracellular andintracellular lycopene in fed-batch fermentation. Both proteomicsand lipidomics analyses of secreted outer membrane vesicles were perfectindicators of hypervesiculation. Changes in the ratio of saturatedfatty acids, unsaturated fatty acids, and cyclopropane fatty acidscoupled with the branching and acyl chain lengths altered the membranefatty acid composition. This ensured membrane fluidity and permeabilityfor in situ lycopene release. The combinatorial deletionof these genes altered the cellular morphology. The structural andmorphological changes in cell shape, size, and length were associatedwith changes in the mechanical strength of the cell envelope. Theenhanced lycopene production and secretion mediated by improved membranepermeability established a cell lysis-free system for an efficientreleasing rate and downstream processing, demonstrating the importanceof vesicle-associated membrane permeability in efficient lycopeneproduction.