LAB and riboflavin overproduction: molecular insights, in vivo probiotic studies, and in situ biofortification potential

Abstract

In Gram-positive bacteria such a LAB, the riboflavin biosynthesis operon is regulated by FMN riboswitch. The exposure of riboflavin-producing strains to roseoflavin has been shown to cause mutations in this aptamer decreasing its stability, even in the presence of the effector, which promotes an antiterminator structure and impairs thes regulatory activity of the riboswitch. This has been used as a strategy to select food-grade LAB strains that have a spontaneous riboflavin-overproducing phenotype. . Several riboflavin-overproducing LAB strains, characterized using in vitro and in vivo models, have been shown to possess probiotic features that allowed them to attenuate ariboflavinosis, intestinal colitis, mucositis and even certain cancers in mice. In addition, vitamin B2-overproducing LAB strains belonging to the species Lactococcus lactis, Lactiplantibacillus plantarum, Limosilactobacillus fermentum, and Leuconostoc mesenteroides have been proposed for the elaboration of riboflavin-enriched fermented foods (i.e., pasta and bread), probiotic bio-fortified fermented foods (i.e., yogurt, and non-dairy products such as soya milk, oat-based, and kefir-like beverages), as well non-conventional unfermented matrices (e.g., fresh-cut fruits). The extraordinary capacity of LAB strains to produce and secrete riboflavin, together with their metabolic versatility and probiotic potential make these strains ideal candidates for applications in the field of fortified and functional foods.