Ligation independent cloning (LIC) as a rapid route to families of recombinant biocatalysts from sequenced prokaryotic genomes

A technique is presented for the high throughput generation of families of recombinant biocatalysts sourced from prokaryotic genomes, providing rapid access to the naturally evolved diversity of enzyme specificity for biocatalyst discovery. The method exploits a novel ligation independent cloning strategy, based on the locally engineered vector pET-YSBLIC and has been used for the rapid generation of a suite of expression plasmids containing genes encoding a family of six Baeyer-Villiger monooxygenases (BVMOs) from Mycobacterium tuberculosis H37Rv (MTb). The six resultant recombinant strains of E. coli B834 (DE3) expressing the genes were assayed for oxygenating activity in respect of the target reaction; the resolution of bicyclo3.2.0]hept-2-en-6-one. The analysis of biotransformations catalysed by growing cells of E. coli was complicated by the production of indole in the reaction mixtures, possibly resulting from the in vivo activity of E. coli tryptophanase. Four of the recombinant strains expressing different BVMOs catalysed the oxidation of one or more of four screening substrates, well above controls that had been transformed with the re-ligated parent vector. One of the recombinant strains, E. coli B834 (DE3) pDB5, expressing the Rv3049c gene from MTb, was found to effectively resolve the target substrate, yielding a 19% yield of (1R, 5S)-(+)-bicyclo3.2.0]hept-2-en-6-one with >95% enantiomeric excess in a 4 L fermentation reaction.