Journal of Agricultural and Food Chemistry最新文献

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.

The access to the enantiopure noncanonical amino acid l-phosphinothricin (l-PPT) by applying biocatalysts is highly appealing in organic chemistry. In this study, a NADH-dependent glutamate dehydrogenase from Lachnospiraceae bacterium (LbGluDH) was chosen for the asymmetric synthesis of l-PPT. Three flexible loops undergoing big conformational shifts during the catalysis were identified and rationally engineered following the initial mutagenesis. The enzyme's specific activity toward the key precursor of l-PPT, 2-oxo-4-[(hydroxy) (methyl) phosphinyl] butyric acid (PPO), was improved from negligible to 9 U/mg, and the K_m value was reduced to 17 mM. The computational analysis showed that the modified loops broadened the enzyme's narrow tunnels, allowing the substrate to access the binding pocket and get closer to the crucial residue D165, thereby enhancing the catalytic process. Utilizing the variant as the catalyst, the preparation of l-PPT achieved a 100% conversion rate within 60 min, coupled with a stereoselectivity exceeding 99.9%, demonstrating its practical capacity for industrial application. Similar enhancement in catalytic activity was obtained applying the same strategy to a typical NADH-dependent GluDH from Pyrobaculum islandicum (PisGluDH), indicating the effectiveness of our strategy for the protein engineering of GluDHs targeted to the biosynthesis of unnatural compounds.

The cornea serves as a vital protective shield for the eye, safeguarding its intricate internal structures from external threats. Damage to the cornea compromises this protective function, triggering inflammation and potentially causing long-term harm. While ginsenoside Rk3 has demonstrated potential for repairing the corneal barrier and reducing inflammation, its effectiveness in treating corneal damage remains relatively unexplored. This comprehensive study uses both in vivo and in vitro models to investigate the therapeutic capabilities of ginsenoside Rk3. Using two models of corneal damage, a benzalkonium chloride-induced mouse model and a high osmolarity-induced human corneal epithelial cell model, we scrutinized the effects of ginsenoside Rk3 treatment. Our results showed that ginsenoside Rk3-treated mice manifested reduced corneal damage and inflammation compared with their untreated counterparts. Furthermore, mice treated with ginsenoside Rk3 exhibited an organized arrangement of corneal cells and diminished stromal layer thickness, indicating reparative properties of ginsenoside Rk3. Additionally, ginsenoside Rk3 increased the expression of tight junction proteins, suppressed inflammatory factors, and decreased HMGB1 protein expression, thereby modulating downstream signaling pathways. Collectively, our findings present compelling evidence that ginsenoside Rk3 is a promising therapeutic option for corneal injury. By repairing the corneal barrier, mitigating inflammation, and modulating specific protein levels, ginsenoside Rk3 opens new avenues for managing corneal damage.

Laccase, a multipurpose biocatalyst, is widely distributed across all kingdoms of life and plays a key role in essential biological processes such as lignin synthesis, degradation, and pigment formation. These functions are critical for fungal growth, plant-pathogen interactions, and maintenance of soil health. Due to its broad substrate specificity, multifunctional nature, and environmentally friendly characteristics, laccase is widely employed as a catalyst in various green chemistry initiatives. With its ability to oxidize a diverse range of phenolic and nonphenolic compounds, laccase has also been found to be useful as a food additive and for assessing food quality parameters. Ongoing advancements in research and technology are continually expanding the recognition of laccase's potential to address global environmental, health, and energy challenges. This review aims to provide critical insights into the applications of laccases in the biotechnology and food industry.