In this thesis, the utilization of cheese whey, a dairy by-product, as sustainable ingredients in sourdough bread making is studied. In this study, the substitution of water with whey in different proportions (0-100%) on three different flours: winter wheat, rye, and oat were tested to assess the fermentation, dough making, and bread quality. Results indicated that whey improved the microbial activity through lactose and protein content, thereby hastening the pH reduction and increasing the acidity in the fermentation. This resulted in improved, texture and shelf life of the bread. Technologically, whey had a positive effect on baking loss, with a better retention of moisture, as well as on loaf volume and shape stability with the best results for 50-100% whey substitution depending on the type of flour used. Overall, the research concludes that the inclusion of whey not only enhances bread quality but also contributes to sustainable food production alongside waste reduction in the dairy industry.