Production of a thermostable alcohol dehydrogenase from Rhodococcus ruber in three different yeast species using the Xplor®2 transformation/expression platform

The Xplor®2 transformation/expression platform was employed for comparative assessment of three different yeast species as hosts for synthesis of a thermostable nicotinamide adenine dinucleotide (NAD+)-dependent medium-chain alcohol dehydrogenase from Rhodococcus ruber strain 219. Using yeast ribosomal DNA (rDNA) integrative expression cassettes (YRCs) and yeast integrative expression cassettes (YICs) equipped with a selection-marker module and one, two or four expression modules for transformation of auxotrophic Arxula adeninivorans, Hansenula polymorpha, and Saccharomyces cerevisiae strains, quantitative comparison of the yield of recombinant alcohol dehydrogenase RR-ADH6Hp in all three species was carried out. In all cases, the RR-ADH6H gene was expressed under the control of the strong constitutive A. adeninivorans-derived TEF1 promoter, which functions in all yeast species analyzed. Recombinant RR-ADH6Hp accumulated intracellularly in all strains tested. The best yields of active enzyme were obtained from A. adeninivorans, with S. cerevisiae producing intermediate amounts. Although H. polymorpha was the least efficient producer overall, the product obtained was most similar to the enzyme synthesized by R. ruber 219 with respect to its thermostability.