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Elaeagnus moorcroftii Wall.ex Schlecht. (EWS) has extensive nutrients and functional active ingredients, which makes it an excellent potential substrate for fermentation. The improvement in the antioxidant activity of Elaeagnus moorcroftii Wall.ex Schlecht. juice (EWSJ) fermented by Bifidobacterium animalis subsp. lactis HN-3 (B.an3) could be attributed to the metabolism and biotransformation of plant-based products by the bacterial strain. To reveal the underlying mechanism, non-targeted metabolomics was applied in this study. After fermentation, the structure of downregulated carbohydrates, amino acids, fatty acids, and flavonoids was changed by Bifidobacterium biotransformation (included four reductions, three hydrolyses, four isomerizations, three deglycosidations, and five other reactions). The structure of these converted upregulated products has a higher antioxidant ability to reduce free radicals than their precursors, such as the flavonoids in the form of hydrolyzed conjugates, amino acids with multiple sulfhydryls or hydroxys, carbohydrates with reactive oxygen on benzene rings and fatty acids with unsaturated bonds, short chains, and glycosides. These findings shed light on the mechanism of the metabolism and biotransformation of EWSJ by B.an3, facilitate the study of the interaction between probiotics and fermented plant-based products, and provide a theoretical basis for the development of Bifidobacterium-fermented plant products with stronger functional activities.

Human gut microbiota interfere with host development and aging. Bifidobacterium is a microbial genus found in the human digestive tract that has probiotic activities such as improving constipation and enhancing immunity. The species and numbers present change with age, but there has been limited research on probiotic gut microbiota at specific ages. This study analyzed the distribution of 610 bifidobacteria in subjects in several age groups (0−17, 18−65, and 66−108 y) using 486 fecal samples and determined the distribution of glycoside hydrolases based on genetic analysis of strains representing 85% of the Bifidobacterium species abundance in each age group. 6’-Sialyllactose is a major component of acidic breast milk oligosaccharides, which can promote human neurogenesis and bifidobacteria growth. Using genotypic and phenotypic association analysis, we investigated the utilization of 6’-sialyllactose by six B. bifidum strains isolated from subjects 0–17 and 18–65 y. A comparative genomic analysis of the six B. bifidum strains revealed differences in genomic features across age groups. Finally, the safety of these strains was evaluated by antibiotic gene and drug resistance phenotype analysis. Our results reveal that the distribution of glycoside hydrolase genes in B. bifidum varies with age, thus affecting the phenotypic results. This provides important insights for the design and application of probiotic products for different ages.

Psychrophiles inhabiting various cold environments are regarded as having evolved diverse physiological and molecular strategies, such as the accumulation of trehalose to alleviate cold stress. To investigate the possible contributions of trehalose metabolism-related enzymes to cold-adaption in psychrotrophic bacteria and enrich the resource bank of trehalose hydrolysis enzymes, a novel cold-adapted GH15 GA-like trehalase (MpTre15A) from psychrotolerant Microbacteriumphyllosphaerae LW106 isolated from glacier sediments was cloned and characterized. The recombinant MpTre15A from M. phyllosphaerae LW106 was expressed and purified in Escherichia coli BL21(DE3). The purified MpTre15A functioned as a hexamer and displayed maximal activity at pH 5.0 and 50 °C. Substrate specificity assay proved MpTre15A only showed hydrolytic activity toward α,α-trehalose. Site-directed mutation verified the key catalytic sites of Glu392 and Glu557 in MpTre15A. The kcat and kcat/Km values of MpTre15A at 4 °C (104.50 s−1 and 1.6 s−1 mM−1, respectively) were comparable to those observed for thermophilic GH15 trehalases at 50 °C, revealing its typical cold-adaptability. MpTre15A showed a trehalose conversion rate of 100% and 99.4% after 10 min and 15 min of incubation at 50 °C and 37 °C, respectively. In conclusion, this novel cold-adapted α,α-trehalase MpTre15A showed potential application for developing therapeutic enzymes, enzyme-based biosensors, and enzyme additives in the fermentation industry.

Acrylamide, a II A carcinogen, widely exists in fried and baked foods. L-asparaginase can inhibit acrylamide formation in foods, and enzymatic stability is the key to its application. In this study, the Escherichia coli L-asparaginase (ECA) stable variant, D60W/L211R/L310R, was obtained with molecular dynamics (MD) simulation, saturation mutation, and combinatorial mutation, the half-life of which increased to 110 min from 60 min at 50 °C. Furthermore, the working temperature (maintaining the activity above 80%) of mutation expanded from 31 °C–43 °C to 35 °C–55 °C, and the relative activity of mutation increased to 82% from 65% at a pH range of 6–10. On treating 60 U/mL and 100 U/g flour L-asparaginase stable mutant (D60W/L211R/L310R) under uncontrolled temperature and pH, the acrylamide content of potato chips and bread was reduced by 66.9% and 51.7%, which was 27% and 49.9% higher than that of the wild type, respectively. These results demonstrated that the mutation could be of great potential to reduce food acrylamide formation in practical applications.