S120: Engineering Candida tropicalis to produce adipic acid from renewable feedstocks

Adipic acid is an important industrial chemical used to make Nylon 6,6 and polyurethane resins for consumer products ranging from fibers for carpets and apparel to shoes and engineering plastics. With an estimated global market of 5 billion pounds per year, it is currently produced from petrochemical sources by nitric acid catalyzed oxidation of cyclohexane.  Bio-based adipic acid would allow the production of completely renewable nylons and polyurethanes and offer significant reduction in GHG emissions compared to traditional petrochemical processes. To this end, we have been engineering the diploid yeast Candida tropicalis to produce bio-based adipic acid from renewable feedstocks. This yeast can normally utilize alkanes or fatty acids as the sole carbon source for growth via cyclic degradation through the β-oxidation pathway. When this pathway is blocked, however, C. tropicalis can convert these substrates at high yield and selectivity to the corresponding dicarboxylic acids via the w-oxidation pathway. Thus, a completely β-oxidation blocked strain would convert the mixed fatty acids from plant-based oils to a mixed dicarboxylic acid product with the same chain-length distribution as the feedstock. We have been engineering both the b-oxidation and w-oxidation pathways to enable selective production of adipic acid from any plant-based oil, regardless of its fatty acid composition.