EPS from Lactobacilli and Bifidobacteria: Microbial metabolites with both technological and health-promoting properties

Abstract

Exopolysaccharides are complex carbohydrates commonly produced by lactic acid bacteria (LAB) and bifidobacteria, which can be released to the medium (EPS) or remained attached to the cell surface (capsular polysaccharide or CPS) (Castro-Bravo et al. 2018b). Although their natural role has not been fully understood yet, it is believed that they may play a beneficial role for the producing bacteria by acting as a physical barrier under stressing environmental conditions, participating in cell interactions, and modifying different ecological niches (Castro-Bravo et al. 2018a). On the other hand, the benefits EPS exert on the host have been widely studied. They proved to have immunomodulatory effects (Ale et al. 2016a; Liu et al. 2017a), regulate the gut microbiota (Bengoa et al. 2020; Yan et al. 2020), protect the host against pathogenic microorganisms (Ale et al. 2016a; Paik et al. 2018), present antioxidant properties (Zhang et al. 2013; Xu et al. 2021), cholesterol-lowering effects (Korcz et al. 2018), and anti-cancer activity in vitro (Xiao et al. 2020a), among others. Moreover, some EPS present interesting rheological properties due to their thickening effects and water-holding capacity within different food matrices (cheese, yogurt, bread, etc.), when produced in situ (Tang et al. 2018; Yilmaz et al. 2015) or added as a food ingredient (Ale et al. 2016b). This last strategy is the least applied by the food industry since the EPS yields obtained from both lactobacilli and bifidobacteria are low in comparison with bacteria of other genera, and the costs of extraction/purification processes are generally high. A summary of the technological and health promoting effects attributed to EPS up to date is shown in Figure 1. It is important to highlight that all these properties strongly depend on the chemical nature of EPS, as it will determine not only their behavior in the host (Castro-Bravo et al. 2018b), but also in different food matrices (Zhou et al. 2019).Considering this double techno-functional role, these polymers have been of great interest to the food industry. In the light of these potential applications of EPS and their producing bacteria, the present chapter intends to summarize the most recent information regarding the functional, technological, and chemical properties of EPS from bifidobacteria and lactobacilli, with the aim of providing scientific evidence that supports their application, highlighting the importance of deepening the current knowledge about these interesting molecules.