Sourdough as a source of technological, antimicrobial, and probiotic microorganisms

Spontaneous sourdough fermentation is an ancestral process used to improve the digestibility of cereals, as well as the taste, aroma, and shelf life of bread. With the advent of scientific progress, sourdough fermentation came to be seen as a biotechnological process by researchers and technologists and became widely studied in different approaches, such as its use as a key processing step of bread making to improve the quality and diversity of the bakery products in terms of technological, functional, nutritional, health and food hygiene, and safety standpoints. Additionally, spontaneous fermentation of cereals mixed with water by adventitious microbiota – mainly from cereal flours and cross-contaminations during baking – are known to result in a naturally selected microbiota composed mainly of synergetic, acid-tolerant yeast and lactic acid bacteria (LAB). Such phenomena led scientists to regard sourdough as an interesting complex cell factory, wherefrom desirable microorganisms and metabolites can be used for numerous biotechnological purposes. This chapter aims at presenting an in-depth review of the potential benefits of sourdough-based microorganisms and metabolites. It starts with a revision of the main microorganisms found in cereals and their dynamics throughout spontaneous sourdough fermentation. Furthermore, it describes the antibacterial, anti-mold, and antioxidant traits of microbial compounds produced during sourdough fermentation. Among those, it was here described as organic acids, alcohols, esters, ketones, aldehydes, exopolysaccharides (EPS), cereal fibers, free amino acids, cyclic peptides, bioactive peptides, bacteriocins and bacteriocin-like inhibitory substances (BLIS), phenolic compounds, and phytoestrogens.