Recently, the drawbacks arising from the overuse of antibiotics have drawn growing public attention. Among them, drug-resistance (DR) and even multidrug-resistance (MDR) pose significant challenges in clinical practice. As a representative of a DR or MDR pathogen, Staphylococcus aureus can cause diversity of infections related to different organs, and can survive or adapt to the diverse hostile environments by switching into other phenotypes, including biofilm and small colony variants (SCVs), with altered physiologic or metabolic characteristics. In this review, we briefly describe the development of the DR/MDR as well as the classical mechanisms (accumulation of the resistant genes). Moreover, we use multidimensional scaling analysis to evaluate the MDR relevant hotspots in the recent published reports. Furthermore, we mainly focus on the possible non-classical resistance mechanisms triggered by the two important alternative phenotypes of the S. aureus, biofilm and SCVs, which are fundamentally caused by the different global regulation of the S. aureus population, such as the main quorum-sensing (QS) and agr system and its coordinated regulated factors, such as the SarA family proteins and the alternative sigma factor σB (SigB). Both the biofilm and the SCVs are able to escape from the host immune response, and resist the therapeutic effects of antibiotics through the physical or the biological barriers, and become less sensitive to some antibiotics by the dormant state with the limited metabolisms.

In this study, the yield of exopolysaccharide (EPS) from Lactobacillus plantarum R301 was optimized using a single-factor experiment and response surface methodology (RSM). After optimization, the EPS yield was increased with a fold-change of 0.85. The significant factors affecting EPS production, as determined through a Plackett–Burman design and Central Composite Design (CCD), were MgSO₄ concentration, initial pH, and inoculation size. The maximum yield was 97.85 mg/mL under the condition of 0.01% MgSO₄, an initial pH 7.4, and 6.4% of the inoculation size. In addition, the EPS exhibited strong antioxidant activity, as demonstrated by its ability to scavenge DPPH, ABTS, and hydroxyl radicals. The scavenging rate was up to 100% at concentrations of 4 mg/mL, 1 mg/mL, and 2 mg/mL, respectively. Moreover, the EPS also exhibited reducing power, which was about 30% that of ascorbic acid when both tended to be stable with the increased concentration. These results suggest that L. plantarum R301 EPS possesses different antioxidant mechanisms and warrants further investigation. In addition to its antioxidant activity, the EPS also demonstrated good anti-inflammatory activity by inhibiting the inflammation induced by lipopolysaccharide (LPS) in RAW 264.7 cells, which could decrease nitric oxide (NO) production and expression of the proinflammatory cytokine Il-6. These findings suggest that L. plantarum R301 EPS could be used as a potential multifunctional food additive in the food industry.

Recent evidence suggests that mulberry leaves have good antioxidant activity. However, what the antioxidant ingredient is and how the ingredient works are still not well understood. In this study, we enzymatically hydrolyze mulberry leaf proteins (MLPs) using neutral protease and find that the mulberry leaf protein hydrolysates (MLPHs) have stronger antioxidant activity compared to MLPs. We separate the core antioxidant components in MLPHs by ion-exchange columns and molecular sieves and identify 798 antioxidant peptides by LC-MS/MS. Through bioinformatics analysis and biochemical assays, we screen two previously unreported peptides, P6 and P7, with excellent antioxidant activities. P6 and P7 not only significantly reduce ROS in cells but also improve the activities of the antioxidant enzymes SOD and CAT. In addition, both peptides are found to exert protective effects against H₂O₂-induced chromatin damage and cell apoptosis. Collectively, these results provide support for the application of mulberry leaf peptides as antioxidants in the medical, food and livestock industries.

A balanced inflammatory response is crucial for the organism to defend against external infections, however, an exaggerated response may lead to detrimental effects, including tissue damage and even the onset of disease. Therefore, anti-inflammatory drugs are essential for the rational control of inflammation. In this study, we found that a previously screened peptide TaY (KEKKEVVEYGPSSYGYG) was able to inhibit the LPS-induced RAW264.7 inflammatory response by decreasing a series of proinflammatory cytokines, such as TNF-α, IL-6, and nitric oxide (NO). To elucidate the underlying mechanism, we conducted further investigations. Western blot analysis showed that TaY reduced the phosphorylation of key proteins (IKK-α/β, IκB-α,NF-κB (P65)) in the TLR4-NF-κB signaling pathway and inhibited the inflammatory response. Furthermore, molecular docking and molecular dynamic simulations suggested that TaY binds to the hydrophobic pocket of MD2 through hydrogen bonding and hydrophobic interactions, potentially competing with LPS for MD2 binding. Collectively, TaY is a promising candidate for the development of novel therapeutic strategies against inflammatory disorders.

Oxidative stress and inflammatory responses often occur concomitantly, and they are key causative factors in various human and animal diseases. Evidence suggests that mulberry leaf protein (MLP) may have potential antioxidant and anti-inflammatory properties, but there are significant challenges in enhancing their bioactivities. In this study, MLP was enzymatically hydrolyzed using papain, protamex, alkaline protease, trypsin, and neutral protease, followed by comprehensive evaluation of the antioxidant capacity, anti-inflammatory properties, and cytotoxicity of the hydrolysates. Our findings revealed that some enzymes significantly enhanced the peptide production and antioxidant activity of MLP (p < 0.01), and its activity was positively correlated with the degree of hydrolysis. Among the five hydrolysates, neutral protease hydrolysate (NeuH) exhibited the best antioxidant properties, with free radical scavenging rates of 71.58 ± 0.42% (ABTS), 26.38 ± 0.15% (OH), and 73.91 ± 0.37% (DPPH) at a concentration of 0.1 mg/mL. In addition, NeuH significantly suppressed IL-6 secretion (p < 0.01) and downregulated mRNA expression of IL-6, iNOS, and COX-2 inflammatory markers. This study not only establishes a correlation between enzymatic parameters and MLP biological functions but also demonstrates the potential of optimized MLP hydrolysates, particularly NeuH, as valuable natural antioxidant and anti-inflammatory ingredients for functional foods or nutraceuticals aimed at mitigating oxidative stress and inflammation-related disorders.

Microbially synthesized postbiotics have unique properties and advantages; however, systematic studies on the efficient production and biological functions of postbiotics from Bacillus subtilis are limited, which greatly restricts their applications. In this study, we obtained a novel crude exopolysaccharide (EPS) postbiotic from Bacillus subtilis H4. We systematically optimized the EPS production strategy using single-factor analysis, Plackett–Burman design, the path of steepest ascent method, and response surface methodology. The optimized EPS yield was significantly improved, with a maximum yield of 15.01 g/L under the addition of 4.12% soy peptone, 8.99% sucrose, and 0.06% MnSO₄. We found that EPS is a neutral, heterogeneous polysaccharide with a pyranose ring, with a molecular weight of 44,304.913 kDa and a melting point of 218 °C. It consists of glucose, galactose, arabinose, glucosamine, and mannose at a molar ratio of 58.85:19.81:14.75:10.89:6.58. EPS exhibits strong antioxidant capacities, scavenging ABTS and DPPH radicals with IC50 values of 1 and 6 mg/mL, respectively. Moreover, it shows notable anti-inflammatory properties, dramatically inhibiting the lipopolysaccharide (LPS)-induced elevation of nitric oxide (NO) levels and over-activation of the TLR4-NF-κB signaling pathway. These findings highlight the potential of EPS as a multifunctional bioactive compound, offering great promise for its application in the food, clinical, and feed industries.