Single-Enzyme Redox-Neutral Oxidation of Alcohols to Carboxylic Acids Using Alcohol Dehydrogenases

Abstract

Oxidation of primary alcohols to carboxylic acids is a fundamental reaction in organic chemistry, traditionally dependent on toxic oxidants and often limited by poor selectivity. In this study, we demonstrate the multifunctional capability of some alcohol dehydrogenases (ADHs) to catalyze both alcohol and aldehyde oxidation while regenerating their NAD⁺ cofactor through concomitant reduction of acetone. Screening of a panel of ADHs, revealed that the enzymes from Paracoccus pantotrophus (Pp-ADH) and Aromatoleum aromaticum (Aa-ADH) have strong overoxidation activity to carboxylic acids. The biocatalytic method was assessed for the efficient oxidation of a panel of 26 structurally diverse primary alcohols into carboxylic acids using a single enzyme, with minimal workup and without the need for further purification. The biotransformation was also scaled up using cell-free extracts, while maintaining high yields. In silico studies provided insights into substrate tolerance, highlighting the structural features that govern enzyme activity. This biocatalytic method provides a scalable, selective, and environmentally friendly alternative to conventional oxidation strategies for primary alcohols to carboxylic acids.