Konvansiyonel olmayan mayalarda glutatyon metabolizmasının kantitatif analizi için sistem biyolojisi yaklaşımı

Non-conventional yeasts (NCY) attract increasing attention in industrial biotechnology context both in applications and fundamental understanding of the metabolism as they are typically richer in their molecular portfolio in comparison to conventional yeasts. Nevertheless, studies on the response of NCYs to different environmental stresses are in their infancy. In particular, oxidative and/or reductive stress typically arise as an inevitable part of the yeast's aerobic style. Yeast cells respond to oxidative stress via enzymatic (SOD, catalase, peroxidase reactions) and/or metabolic (glutathione or uric acid production pathways) through multi-omics and complex responses. Response to reductive stress, in turn, may result from increased antioxidant levels. Both typically disturb the intracellular redox balance. Departing from the question of how non-conventional yeasts respond to oxidative stress, this thesis focuses on the quantitative investigation of intracellular amino acids and glutathione levels in the NCYs. Following the systems biology approach, the generated data on fermentation profiles, fluxome, and targeted metabolome, as well as transcriptome data from literature, are collectively taken into account in response to both oxidative and reductive stresses for conventional and the non-conventional yeasts. There was a discrepancy between organisms at low concentrations of amino acids. Furthermore, the amino acid levels are lower in the 150L scale by a factor of 3-5 for both yeasts. Oxidative stress induces a different short-term response in amino acid levels in both yeasts cultivated in a chemostat. The glutathione levels increased with 5 mM of H2O2-induced oxidative stress at the chemostat in S. cerevisiae. The results obtained in this study shed light on the different responses of these yeasts to hydrogen peroxide-induced oxidative stress. Comparing batch to batch, sample to sample, and injection to injection variances, it can be concluded that the targeted quantitative metabolomics approach was successfully applied in this thesis. Finally, yeast strains overproducing GSH are obtained via the classical UV-mutagenesis approach. These strains have up to a 50 percent increase in GSH content compared to the wild-type strain.