Oxidative stress-resistance assay for screening yeast strains overproducing heterologous proteins

Many natural proteins have been developed into drugs and produced for direct application. Identifying improved hosts to achieve high-level heterologous protein production is a challenge in the study of heterologous protein expression in recombinant yeast. In this study, a novel high-throughput assay to screen such overproducing Saccharomyces cerevisiae strains was systematically developed. The protocol designed was based on screening host strain derivatives with increased superoxide dismutase dependent resistance to oxidative stress. Yeast cells transformed with recombinant plasmid carrying SOD1 gene as a reporter responded exquisitely to oxidative stress induced by elevated concentrations of paraquat. Improved yeast strains resulting from screening clones subjected to genome shuffling through selective pressure argue for a more effective screening system compared with traditonal selection. Moreover, this approach can be employed in general biochemical analysis without utilization of flow cytometry or well plate reader. Therefore, it is expected that the high-throughput assay would make superior strains producing heterologous proteins.