Engineering carboxylic acid reductases and unspecific peroxygenases for flavor and fragrance biosynthesis.

Emerging consumer demand for safer, more sustainable flavors and fragrances has created new challenges for the industry. Enzymatic syntheses represent a promising green production route, but the broad application requires engineering advancements for expanded diversity, improved selectivity, and enhanced stability to be cost-competitive with current methods. This review discusses recent advances and future outlooks for enzyme engineering in this field. We focus on carboxylic acid reductases (CARs) and unspecific peroxygenases (UPOs) that enable selective productions of complex flavor and fragrance molecules. Both enzyme types consist of natural variants with attractive characteristics for biocatalytic applications. Applying protein engineering methods, including rational design and directed evolution in concert with computational modeling, present excellent examples for property improvements to unleash the full potential of enzymes in the biosynthesis of value-added chemicals. • Carboxylic acid reductases (CARs) directly reduce carboxylic acids into aldehydes without a second enzyme for substrate activation. • Unspecific peroxygenases (UPOs) are self-sufficient mono peroxygenases that catalyze similar reactions as P450 enzymes. • Both groups of enzymes have broad substrate scopes and perform chemistries that are challenging to chemical methods. • We present enzyme engineering examples that improved and/or altered the catalytic property or stability of these enzymes. • The engineering achievements are steppingstones towards the ultimate industrial syntheses using CARs and UPOs. [ABSTRACT FROM AUTHOR]