Novel Catabolic Pathway of Quercetin-3-O-Rutinose-7-O-α-L-Rhamnoside by Lactobacillus plantarum GDMCC 1.140: The Direct Fission of C-Ring

Akkermansia muciniphila Growth Promoted by Lychee Major Flavonoid through Bacteroides uniformis Metabolism

Akkermansia muciniphila (A. muciniphila) possesses health-promoting properties. Nevertheless, A. muciniphila enrichment remains a challenging endeavor. Quercetin-3-O-rutinose-7-O-α-l-rhamnoside (QRR), a flavonoid found in lychee pulp, has a unique double-substituted glycosylated structure, requiring a specific intestinal microbiota for effective metabolism. Here, QRR was fermented using a coculture of Bacteroides uniformis and A. muciniphila, and the interactions between the two were elucidated in terms of QRR regulation of microbial growth changes and metabolic properties. The results demonstrated that QRR effectively promoted the proliferation of A. muciniphila based on the metabolic action of B. uniformis in vitro, which was evidenced by a notable increase in the number of viable bacteria. Furthermore, the coculture sample exhibited a significant increase in SCFAs. Qualitative analysis of metabolites by UPLC-ESI-Triple-TOF-MS/MS showed that B. uniformis could release sugars on QRR to produce quercetin-3-O-glucoside-7-O-α-rhamnoside and further quercetin. In the coculture and B. uniformis culture, quercetin was converted to taxifolin, which was identified as a crucial intermediate in the metabolism of QRR. Notably, the metabolite kaempferol was only detected in the coculture. The present study reveals the interaction between QRR and the coculture of A. muciniphila and B. uniformis, providing a practical basis for the potential prebiotic value of QRR.

Lacticaseibacillus casei- and Bifidobacterium breve-fermented red pitaya promotes beneficial microbial proliferation in the colon

Red pitaya has been demonstrated to strongly inhibit α-glucosidase activity; however, the impact of red pitaya fermentation by probiotic bacteria on α-glucosidase inhibition remains unclear. In this study, six strains of lactic acid bacteria (Lactiplantibacillus plantarum, Lacticaseibacillus rhamnosus, Lactobacillus bulgaricus, Lacticaseibacillus casei, Lactobacillus acidophilus and Streptococcus thermophilus) and one strain of Bifidobacterium breve were utilized for the fermentation of red pitaya pulp. The α-glucosidase and α-amylase inhibition rates of red pitaya pulp were significantly greater after fermentation by Bifidobacterium breve and Lacticaseibacillus casei than by the other abovementioned strains. The LC group exhibited an α-glucosidase inhibition rate of 99%, with an α-amylase inhibition rate of 89.91%. In contrast, the BB group exhibited an α-glucosidase inhibition rate of 95.28%, accompanied by an α-amylase inhibition rate of 95.28%. Moreover, red pitaya pulp fermented with Bifidobacterium breve and Lacticaseibacillus casei produced a notable quantity of oligosaccharides, which was more than three times greater than that in the other groups. Furthermore, 16S rRNA high-throughput sequencing analysis was conducted to assess alterations in the composition of the gut microbiota. This revealed an increase in the abundance of Lactobacillus and Faecalibacterium in the pulp fermented by Bifidobacterium breve and Lacticaseibacillus casei, whereas the abundance of Sutterella decreased. Further analysis at the species level revealed that Bifidobacterium longum, Faecalibacterium prausnitzii, and Lactobacillus zeae were the dominant strains present during colonic fermentation. These results indicate a beneficial health trend associated with probiotic bacterial fermentation of red pitaya pulp, which is highly important for the development of functional products.

Screening of Lactiplantibacillus plantarum NML21 and Its Maintenance on Postharvest Quality of Agaricus bisporus through Anti-Browning and Mitigation of Oxidative Damage

Browning and other undesirable effects on Agaricus bisporus (A. bisporus) during storage seriously affect its commercial value. In this study, a strain, Lactiplantibacillus plantarum NML21, that resists browning and delays the deterioration of A. bisporus was screened among 72 strains of lactic acid bacteria (LAB), and its preservative effect was analyzed. The results demonstrated that gallic acid, catechin, and protocatechuic acid promoted the growth of NML21, and the strain conversion rates of gallic acid and protocatechuic acid reached 97.16% and 95.85%, respectively. During a 15 d storage of the samples, the NML21 treatment displayed a reduction in the browning index (58.4), weight loss (2.64%), respiration rate (325.45 mg kg-1 h-1), and firmness (0.65 N). The treatment further inhibited Pseudomonas spp. growth and polyphenol oxidase activity, improved the antioxidant capacity, reduced the accumulation of reactive oxygen species, and reduced the malonaldehyde content and cell membrane conductivity. Taken together, the optimized concentrations of NML21 may extend the shelf life of A. bisporus for 3-6 d and could be a useful technique for preserving fresh produce.

Lychee pulp phenolics fermented by mixed lactic acid bacteria strains promote the metabolism of human gut microbiota fermentation in vitro

Lychee pulp phenolics possess excellent biological activities, however, changes in phenolic substances after microbial treatments are unknown. Herein, lychee pulp was fermented by Lactobacillus plantarum, Lactobacillus rhamnosus, and a mixed strain of the two, followed by an investigation of the products' colonic fermentation. In comparison to single-strain fermentation, mixed-strain fermentation significantly increased catechin and quercetin. In addition, lychee phenolics fermented by mixed strains were more conducive to the growth of gut microbiota. The results of HPLC-DAD showed that colonic fermentation further promoted the release of lychee phenolics. There was a notable increase in the content of gallic acid and quercetin, while multiple phenolics were degraded. Quercetin-3-O-rutinose-7-O-α-L-rhamnoside (QRR) and rutin were catabolized into quercetin by gut microbiota, and 4-hydroxybenzoic acid was produced from the metabolism of QRR and procyanidin B2. Lychee phenolics fermented by mixed lactic acid bacteria were easily metabolized and transformed by gut microbiota. These findings indicate that lychee pulp fermented by mixed lactic acid bacteria possesses probiotic potential, which is of great significance for the development of functional probiotic products.