Broadening the repertoire of microbial aldo-keto reductases: cloning and characterization of AKR3B4 from Rhodotorula mucilaginosa LSL strain

Abstract

Aldo-keto reductases (AKRs) are nicotinamide-dependent enzymes that catalyze the transformation of aldehydes and ketones into alcohols. They are spread across all phyla, and those from microbial origin have proved to be highly robust and versatile biocatalysts. In this work, we have discovered and characterized a microbial AKR from the yeast Rhodotorula mucilaginosa by combining genome-mining and expression assays. The new enzyme, named AKR3B4, was expressed by a simple protocol in very good amounts. It displays a selective substrate profile exclusively transforming aldehydes into alcohols. Also, AKR3B4 shows very good stability at medium temperatures, in a broad range of pH values and in the presence of green organic solvents. Conversion assays demonstrate it is an excellent biocatalyst to be used in the synthesis of aromatic alcohols, and also to produce furan-3-ylmethanol and the valuable sweetener xylitol. These results show that AKR3B4 displays attractive features so as to be used in chemoenzymatic processes.