Lactobacillus exopolysaccharides: New perspectives on engineering strategies, physiochemical functions, and immunomodulatory effects on host health

Recent scientific research has examined the many ways probiotics have a positive effect on human health; especially lactic acid bacteria have received considerable attention due to their ability to produce exopolysaccharides which may be involved in probiotic activity. Lactobacillus exopolysaccharides comprise repeating mono/oligosaccharide subunits that have complicated structure and characteristics. The exopolysaccharide-producing Lactobacillus species are extensively used as starter cultures to produce fermented food products due to their excellent technological characteristics. However, it is their immunoregulatory potential that has gained scientific attention in that it strictly correlates to the chemical structure and configuration of these bacterial exopolysaccharides. Therefore this review highlights the relationship of structure and function of lactic acid bacterial exopolysaccharides with an emphasis on the immunoregulatory potential. It summarizes the details of various in-vitro/in-vivo models used to evaluate exopolysaccharides immunomodulatory potential focusing on the exopolysaccharides structural-immunity relationship. Engineering strategies are proposed for improving production yield. The review concludes with a summary of how exopolysaccharides play a role in the food industry, using yogurt as an example. We searched databases such as the University Network Database, PubMed, Science Direct, SciFinder, Web of Science, Scopus, MedLine, ResearchGate, and Google Scholar to identify studies on role of Lactobacillus and their metabolites especially exopolysaccharide in functional food and its immunoregulatory potential. Lactobacillus exopolysaccharides contain various functional groups (such as hydroxyl group, phosphate group, and carbonyl group) which were helpful to exert their immunomodulatory, antimicrobial, antioxidant, and anticancer activities. Collectively, the data suggest that Lactobacillus exopolysaccharides can be used as nutritional and therapeutic agents to regulate the host immune system, in turn helping to combat various disorders including cancer, diabetes, and hypertension. Overall, a huge gap in knowledge was apparent, suggesting that further in vitro and in vivo investigations are needed to document the immunomodulatory potential of Lactobacillus exopolysaccharides supplemented functional foods.