Biocatalysis with In-Situ Product Removal Improves p-Coumaric Acid Production

Natural and pure p-coumaric acid has valuable applications, and it can be produced via bioprocessing. However, fermentation processes have so far been unable to provide sufficient production metrics, while a biocatalytic process decoupling growth and production historically showed much promise. This biocatalytic process is revisited in order to tackle product inhibition of the key enzyme tyrosine ammonia lyase. In situ product removal is proposed as a possible solution, and a polymer/salt aqueous two-phase system is identified as a suitable system for extraction of p-coumaric acid from an alkaline solution, with a partition coefficient of up to 13. However, a 10 % salt solution was found to reduce tyrosine ammonia lyase activity by 19 %, leading to the need for a more dilute system. The cloud points of two aqueous two-phase systems at 40 °C and pH 10 were found to be 3.8 % salt and 9.5 % polymer, and a 5 % potassium phosphate and 12.5 % poly(ethylene glycol-ran-propylene glycol) mW~2500 system was selected for in situ product removal. An immobilized tyrosine ammonia lyase biocatalyst in this aqueous two-phase system produced up to 33 g/L p-coumaric acid within 24 hours, a 1.9-fold improvement compared to biocatalysis without in situ product removal.