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The influence of riboflavin (B2)–overproducing lactobacilli on the antioxidant status, isoflavone conversion, off-flavor reduction, amino acid profile, and viscosity of B2-bio-enriched fermented soymilk was investigated. Results showed that B2 in fermented soymilk was notably increased from 0.2 to 3.8 μg/mL for Lactobacillus fermentum UFG169 and to 1.9 μg/mL for Lactobacillus plantarum UFG10. The apparent viscosity significantly changed with rising acidity and agglutination of protein. The off-flavor volatile substances (hexanal and nonanal) were significantly reduced in fermented soymilk. Furthermore, a large amount of glucoside form isoflavones was deglycosylated into bioactive aglycones after 4 h up to 32 h. B2 content and isoflavones significantly improved the antioxidant status of soymilk. Partial least squares regression analysis correlated the strain activity and fermentation time with the improved nutritional and functional soymilk qualities. This study demonstrated the strategy for strain development for B2-bio-enriched fermentation to extend the health-promoting benefits of soymilk and soy-related foods. Key points: • B2-enriched fermentation enhanced the nutrition and functional status of soymilk. • Fermentation time significantly affected the apparent viscosity of fermented soymilk. • Off-flavor volatile substances were significantly reduced or even diminished. • Increased B2and bioactive isoflavones contributed to improved antioxidant potential. [ABSTRACT FROM AUTHOR]

[Display omitted] • Okara immobilized B 2 vitamin producing probiotic lactobacilli UFG10 could improve the functional properties of soymilk. • Okara immobilization not only allowed the bacterial protection but also elevated their metabolism. • Enhanced aglycone isoflavones release and improved B 2 production were reported in the soymilk. • Okara immobilized B 2 producing lactobacilli improved the antioxidant status of soymilk. • AFM revealed higher soy protein aggregation and lower protein molecular chains indicating better digestibility. Due to highly nutritious and well-known prebiotic nature, okara (soy by-product) can improve the physiological benefits of probiotic consumption by enhancing the physicochemical stability and bioavailability of bacteria and metabolites, partially in food matrices and then in gastrointestinal tract. Initially, vitamin B 2 producing probiotic Lactobacillus plantarum UFG10 was immobilized with 4% okara for soy milk fermentation. SEM micrographs showed firm adherence of UFG10 to okara surface depicting efficient immobilization. Soy milk fermented with okara immobilized UFG10 showed enhanced β -glucosidase activity, stimulating the biotransformation of isoflavones from glucosides (daidzin, from 27.78 to 9.84 μg/mL; genistin, from 32.58 to 8.33 μg/mL) to aglycones (daidzein, from 0.19 to 30.84 μg/mL; genistein, from 1.42 to 33.10 μg/mL) and higher B 2 production (1.53 μg/mL, 12 h) confirmed by HPLC. Okara addition and B 2 enrichment could yield relatively higher antioxidant strength than control soy milk. PLSR correlation revealed the effects of okara and B 2 on the functional properties of soy milk. After okara immobilization, soy milk showed higher soy protein digestibility after in vitro digestion for 225 min, higher aggregation, and lower protein molecular chains, qualitatively confirmed with Atomic force microscope. Okara immobilized bacterial cells exhibited relatively greater resistance up to 55.1% (p < 0.05) in simulated GIT, indicating okara as an ideal substrate for an efficient immobilization which ultimately improved the fate of soy B 2 and protein bioaccessibility and functional products such as isoflavones for micro structural design of soy milk with improved nutrition and digestibility. [ABSTRACT FROM AUTHOR]

The delivery of beneficial bacteria to the gut microbiome holds a promise to avert and treat diseases such as ariboflavinosis. Nevertheless, adverse gastrointestinal (GI) conditions, a high concentration of reactive oxygen species (ROS), exhausted mucus layer, constant peristalsis of the gastrointestinal tract, and complex pathological microenvironment result in low oral bioavailability lead to limited intestinal colonization of probiotics and affect their related health benefits. Herein, we established a bio-based strategy of double-layer gelatin-mucin-alginate and chitosan-mucin-alginate microcapsules that endow the transplanted riboflavin (vitamin B 2) over-producing strain Lactobacillus plantarum B2 with robust resistance to adverse environments and remarkable adhesiveness to the intestine. The outer gelatin (or chitosan) membrane was observed by building a gelatin-genipin (or chitosan-genipin) fluorescent complex. We demonstrated that co-encapsulating with mucin and the secondary coating of gelatin or chitosan could effectively maintain the regular surface morphology of gel beads and protect probiotics during the lyophilization process, possibly by improving the internal cross-linking and mechanical strength of the microcapsules. The encapsulated probiotic strain was endowed with strong resistance during storage, simulated gastrointestinal digestion fluid, and ROS exposure. In addition, co-embedded mucin augmented the adherence rate of L. P. B2 on the simulated intestinal mucus. Most importantly, microcapsule encapsulation not only retained the probiotic potential of L. P. B2 but also improved the B 2 production during soymilk fermentation. Altogether, the encapsulation strategy can be used as an effective way to deliver explicit probiotics to the gut microbiota for the intestinal colonization of probiotics to deliver B 2 in the human gut. [Display omitted] • Double-layer mucin microcapsules for the oral delivery of probiotics were developed. • Double-layer microcapsules improved the in vitro survival of the L. P. B2 strain. • The encapsulated L. P. B2 acquired strong resistance to simulated GI fluid and ROS. • Co-embedded mucin enhanced the simulated intestinal mucus adhesion of L. P. B2. • Microcapsules encapsulated L. P. B2 could maintain the probiotic properties. [ABSTRACT FROM AUTHOR]