A review of structure-activity relationship, enzymatic and genetic modulation of exopolysaccharides from lactic acid bacteria

Lactic acid bacteria (LAB) exopolysaccharides (EPS) reveal high safety and multiple activities, and are typical postbiotics produced by LAB during fermentation. In this paper, 6583 articles on LAB-EPS from Web of Science and Elsevier databases were retrieved, and 236 articles related to this review were screened. The EPS from 90 LAB strains were summarized in terms of their extraction methods, yield, molecular weight, monosaccharide composition, glycosidic bond configuration and the structural and activity relationships (SARs). However, there exist great challenges as for the low yield and high cost in EPS production. Therefore, this review further elaborated the mechanism of EPS secretion, the anabolic pathway of EPS, the structure and mechanism of key enzymes involving in EPS synthesis process, the prospect of gene regulation for EPS secretion, and proposed the engineering strategies for increasing EPS yield or tailored EPS design in recent years. In addition, CRISPR/Cas9 gene editing technology was also discussed in the production control of EPS in LAB. Finally, the engineering strategy of increasing EPS yield in recent years was proposed. This work might provide important theoretical support for the production and application of LAB-based EPS.