Production of Adipic Acid from Sugar Beet Residue by Combined Biological and Chemical Catalysis

Adipic acid is one of the most important industrial dicarboxylic acids and is used mainly as a precursor to nylon-6,6. Currently, commercial adipic acid is produced primarily from benzene by a chemical route that is associated with environmental, health, and safety concerns. Herein, we report a new process to produce adipic acid from an inexpensive renewable feedstock, sugar beet residue by combining an engineered Escherichia coli strain and Re-based chemical catalysts. The engineered E.coli converted d-galacturonic acid to mucic acid, which was precipitated easily with acid, and the mucic acid was further converted to adipic acid by a deoxydehydration reaction catalyzed by an oxorhenium complex followed by a Pt/C-catalyzed hydrogenation reaction under mild conditions. A high selectivity to the free acid products was achieved by tuning the acidity of the Re-based catalysts. Finally, adipic acid was produced directly from sugar beet residue that was hydrolyzed enzymatically with engineered E.coli and two chemical catalysts in a yield of 8.4 %, which signifies a new route for the production of adipic acid.