Modulating Cell Permeability for Whole-Cell Biocatalysis in Chemical Synthesis (TSE03-D)

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One fundamental problem in whole-cell biocatalysis is the impermeability of cell membranes to diverse substrates of industrial interests, which greatly limits the reaction rate, and in worst scenarios makes the intracellular enzyme network completely inaccessible. This research proposes two novel strategies to the permeability issue. In the first strategy, an E.coli Lipid A mutant with modified biosynthesis of lipopolysaccharides will be used to alter the outer membrane permeability. In the second strategy, membrane-active peptides that modify membrane permeability will be used. These peptides will be generated by directed evolution methods with carefully designed selection and screening procedures. The modulation of cell permeability could be effected by varying cation concentrations, permeabilizing peptide expression level or by using a peptide sequence with a different membrane permeabilizing activity. By removing permeability barriers, the whole-cell biocatalysts can be made accessible to synthetic substrate of various types, hydrophobic and large hydrophilic substrates that cells do not normally have mechanisms for uptake.