Yeast Strains from Sourdough as Potential Clean-Label Starters for Fermentation Processes

Fermented products have been produced and used for a long time. However, nowadays, using the theoretical and practical knowledge available, the objectives in the field aim to exploit the technological and functional properties of these products in foods, feed, and bioingredients with a great impact on the microbiological stability, safety, and bioactivity, contributing also to the products’ diversification. In bioprocessing, the main factors responsible for the techno-functional positive effects are the substrate composition, the type and biochemical properties of the microbiota, respectively the physicochemical conditions associated with the process. Such variations can induce qualitative and quantitative changes on the metabolites’ spectrum, concentration, and bioactive potential. The individual and synergistic effects of these factors must be considered for efficient bioprocesses design. Sourdough’s fermentation is ensured by lactic acid bacteria and yeast strains, as the most important microorganisms from the ecosystem. Each microbial strain contributes with its unique metabolic activity and interspecific relationships established with other microbial strains from the symbiotic consortium. Therefore, yeast strains can lead to the development of clean-label starter cultures to functionalize the fermented products. This chapter gives an updated overview of the yeast strains from sourdoughs’ microbiota and their beneficial impact on innovative functional products or bioingredients formulations to enhance simultaneously the in vitro and in vivo features. Furthermore, the mechanisms behind some bioprocesses (fermentation, bioconversion, or autolysis) involving yeast strains were discussed. Yeasts’ probiotic potential by viable cells, respectively the yeasts-derived metabiotics (prebiotics, probiotics, postbiotics, and paraprobiotics) obtainment were highlighted taking into consideration their benefits and specificity.