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.

Fermented milk with water-in-oil-in-water (W/O/W) Lactiplantibacillus plantarum L3 microcapsules prepared with modified low methoxyl pectin (mLMP) and a commercial starter culture was stored 4 ℃ for 0, 7, 14 or 21 days prior to simulated gastrointestinal digestion. To investigate the stress response of L. plantarum L3 to fermentation, storage and simulated gastrointestinal environments, viable count was measured, cee morphology was observed, and the fatty acid composition of the cell membrane and intracellular amino acid composition were analyzed. Results showed that after storage for 21 days and simulated gastrointestinal digestion, the viable count was maintained at about 9.74 (lg(CFU/mL)) and the cell structure remained intact and clear. Alanine, glutamic acid and aspartic acid were the most abundant amino acids in microencapsulated L. plantarum L3 at all storage periods. The ratio of unsaturated to saturated fatty acids in the cell membrane increased firstly and then decreased with storage time, but was always higher than that of free L. plantarum L3. In conclusion, W/O/W microencapsulation can improve the survival rate of L. plantarum L3 in adverse environments such as yoghurt, cold storage, gastric acid, bile fluid and intestinal fluid, which provides a scientific basis for the application of functional strains in food carriers.

In our previous study, we have isolated Lactoplantibacillus plantarum L₃ (GenBank accession No. MT781360) which can secret bacteriocin L3 with broad-spectrum antibacterial activities. This work aimed to illustrate the antibacterial mechanism of bacteriocin L3 and predict the functionalities of the L. plantarum L₃ strain through whole genome analysis. Preliminary exploration of the bacteriostatic mechanism showed that bacteriocin L3 destroyed the cell membrane integrity and led to the extravasation of the cell contents, leading to cell death. The sequencing results showed that the genome of Lactobacillus plantarum L₃ was 3 187 020 bp in size, with a GC content of 44.57%. Overall, 3 024 encoding genes were annotated, with a sequence length of 2 679 162 bp, accounting for 84.06% of the total genome length. The strain has strong reproductive and metabolic abilities and high safety. The bacteriocin gene cluster analysis showed that the bacteriocins L3 belonged to the class IIb bacteriocins. This work might provide a theoretical basis for the application of this strain in the food industry, especially its potential use in dairy products.