Chemoenzymatic two-step synthesis of tartaric acid employing glucose oxidase in combination with bimetallic AuPt/TiO2 catalyst

Tartaric acid (TA) is a crucial hydroxy-carboxylic acid chelating agent extensively employed in the pharmaceutical, food, dye, and energy industries. The utilization of glucose oxidation for TA synthesis represents an appealing yet challenging, environmentally-friendly approach. In this study, we developed a two-step chemoenzymatic strategy involving the efficient generation of gluconic acid (GA) through glucose oxidase (Gox) catalysis, followed by chemical decarboxylation to synthesize TA from GA. To optimize the production efficiency of GA and eliminate substrate inhibition in chemocatalysis, we successfully engineered a quadruple variant GoxM10 by implementing rigidifying structure strategies and refining the pH curve. This resulted in a substantial increase in the conversion rate of GA from 45% to 100%, along with improved thermo- and pH stability, as well as enhanced catalytic efficiency. Subsequently, durable bimetallic catalysts were designed for the conversion of Gox-bioconverted GA (bio-GA) to TA. Given the presence of impurities such as acetic acid and sodium acetate in bio-GA, which impacted the selectivity of TA, our focus was on investigating the influence of impurities in bio-GA on the performance of a bimetallic AuPt/TiO 2 catalyst and elucidating an inhibition mechanism that reveals a strong interaction between acetate and Au site, resulting in the formation of a complex compound while promoting uncontrollable C-C cleavage reactions. Through employing a chemoenzymatic two-step strategy, we successfully achieved an environmentally friendly and sustainable route from glucose to TA. This study provides valuable insights into catalyst design and optimization of reaction routes for renewable carboxylic acids and their derivatives synthesized through chemoenzymatic methods. This study utilizes glucose as a substrate and combines durable glucose oxidase with bimetallic catalysts to construct a chemoenzymatic cascade reaction for the green synthesis of tartaric acid.