Assessment of Schwanniomyces occidentalis as a host for protein production using the wide-range XplorA®2 expression platform

The wide-range transformation/expression platform, XplorA (R) 2, was employed for the assessment of Schwanniomyces occidentalis as a potential producer of the recombinant proteins human IFN alpha 2a (IFN alpha 2a) and S. occidentalis fructofuranosidase (SFfase), and its efficiency was compared to that of Arxula adeninivorans. ADE2 and URA3 genes from both yeast species were isolated, characterized and used as selection markers in combination with the IFN alpha 2a and SFfase expression modules, which used the strong constitutive A. adeninivorans-derived TEF1 promoter. Yeast rDNA integrative expression cassettes and yeast integrative expression cassettes equipped with a selection marker and expression modules were transformed into auxotrophic S. occidentalis and A. adeninivorans strains and a quantitative comparison of the expression efficiency was made. Whilst IFN alpha 2a was mainly accumulated extracellularly (> 95 %) in A. adeninivorans, extracellular SFfase (> 90 %) was detected in both yeast species. The DNA composition of the selection marker modules and expression modules, especially their open reading frame codon usage, affects auxotrophy recovery as well as protein expression. Auxotrophy recovery was only achieved with selection marker modules of the homologous gene donor yeast. The concentration of recombinant IFN alpha 2a was fivefold higher in A. adeninivorans (1 mg L-1), whereas S. occidentalis accumulated 1.5- to 2-fold more SFfase (0.5 Units ml(-1)). These results demonstrate the extension of the use of the wide-range expression platform XplorA (R) 2 to another yeast species of biotechnological interest.