Effects of lipocalin expression on environmental stress response in Saccharomyces cerevisiae

Many industries rely on the growth and productivity of Saccharomyces cerevisiae. Unfortunately, industrial fermentation processes create a myriad of stresses which yeasts must overcome, including conditions like the accumulation of oxidative, osmotic, and saline stressors as well as high temperatures and high ethanol concentrations. This research sought to evaluate whether or not transforming these yeasts with genes that encode lipocalins—a class of small proteins that are capable of binding, transporting, and/or sequestering small, hydrophobic molecules—would increase the stress tolerance of transformants relative to controls that were not transformed. The genes encoding Arabidopsis thaliana temperature induced lipocalin (At-TIL), human odorant binding protein 2A (OBP2A), and human odorant binding protein 2B (OBP2B) were cloned in Escherichia coli, ligated into the yeast shuttle vector, and transformed into wild type (BY4743) and knockout (ALD3- and ALD4-) strains of S. cerevisiae. Transformants and their respective controls were then subjected to phenotyping to elucidate any changes in stress tolerance to the five stresses listed above. BY4743::OBP2A and BY4743::OBP2B performed significantly better than their controls under oxidative stress and heat stress. At-TIL did not significantly change the response of the wild type to any of the evaluated stresses. The continuation of this research could ultimately lead to the production of a yeast strain that is highly tolerant to the many stresses faced by yeasts during industrial fermentation processes, improving efficiency and cost-effectiveness for the many industries that are reliant on the success of this microorganism.