High vitamin B₂ production by the Lactiplantibacillus plantarum B2 strain carrying a mutation in the aptamer P1 helix of the FMN-riboswitch that regulates expression of the bacterial rib operon

Abstract

Manufacturing of probiotics and functional foods using lactic acid bacteria that overproduce vitamin B2 has gained growing interest due to ariboflavinosis problems affecting populations of both developing and affluent countries. Two isogenic Lactiplantibacillus plantarum strains, namely a riboflavin-producing parental strain (UFG9) and a roseoflavin-resistant strain (B2) that carries a mutation in the FMN-aptamer of the potential rib operon riboswitch, were analyzed for production and intra- and extracellular accumulation of flavins, as well as for regulation of the rib operon expression. Strain B2 accumulated in the medium one of the highest levels of riboflavin+FMN ever reported for lactic acid bacteria, exceeding by ~25 times those accumulated by UFG9. Inside the cells, concentration of FAD was similar in both strains, while that of riboflavin+FMN was ~6-fold higher in B2. Mutation B2 could decrease the stability of the aptamer's regulatory P1 helix even in the presence of the effector, thus promoting the antiterminator structure of the riboswitch ON state. Although the B2-mutant riboswitch showed an impaired regulatory activity, it retained partial functionality being still sensitive to the effector. The extraordinary capacity of strain B2 to produce riboflavine, together with its metabolic versatility and probiotic properties, can be exploited for manufacturing multifunctional foods.

Riboflavin Bioenriched Soymilk Alleviates Oxidative Stress Mediated Liver Injury, Intestinal Inflammation, and Gut Microbiota Modification in B2 Depletion–Repletion Mice

“…L. plantarum B2 (CECT 8328, Valencia, Spain), B 2 overproducing strain was characterized for its probiotic potential in vitro and in vivo and used in the production of B 2 -enriched foods. ,, In continuation of our previous report on B 2 bioenriched soymilk fermented with B 2 overproducing L. plantarum B2 (CECT 8328, Valencia, Spain), , herein, we established the B 2 deficient mice model to evaluate the reversion effects of normal soymilk, commercial B 2 , and B 2 bioenriched soymilk on B 2 deficiency biomarkers (phenotypic symptoms and EGRAC), serum oxidative stress markers (SOD, CAT, MDA, T-AOC), and inflammation symptoms (tissue structure of the liver and colon), which were confirmed at mRNA and protein levels. Further, changes in mice intestinal microflora (diversity and variation analysis of gut microbiota and cecal short-chain fatty acid content) responding to oxidative stress and inflammation were also evaluated.…”

Whole genome sequence of Lactiplantibacillus plantarum strain HA9 isolated from conventional Iraqi cheese: First report

“…For instance, the L. plantarum B2 strain has a mutation in the FMN-aptamer of the riboswitch, which regulates the expression of the rib operon. The strain benefits from the increased production and accumulation of riboflavin and FMN as sources of vitamin B2, but this mutation also decreases the riboswitch's regulatory activity and makes the strain more susceptible to roseoflavin, a riboflavin analog that prevents bacterial growth [13]. Thus, it is essential to establish the genetic identity of the strain both before and throughout manufacturing.…”