Unraveling the Antibacterial Mechanism of Plasma-Activated Lactic Acid against Pseudomonas ludensis by Untargeted Metabolomics

Transcriptomic and metabolomic analyses of the antimicrobial activity of phenoxyethanol against phylotype IA1 and II Cutibacterium acnes

AIMS

Phenoxyethanol is a broad-spectrum antimicrobial agent widely used in cosmetic formulations. However, its antibacterial effects on different skin bacteria, particularly the predominant Cutibacterium acnes and its various phylotypes, remain unclear. The objective of this study was to examine the antimicrobial effects of phenoxyethanol on C. acnes and explore the mechanism.

METHODS AND RESULTS

Phenoxyethanol exhibited strong antimicrobial effects against both C. acnes ATCC6919 (phylotype IA1) and CCSM0331 (phylotype II), achieving a minimum inhibitory concentration (MIC) of 0.5% (v/v). Sub-MIC concentrations showed a stronger inhibitory effect on CCSM0331. RNA-seq and metabolomic analyses revealed that phenoxyethanol disrupted cell membrane integrity and influenced essential metabolic pathways, such as energy metabolism, amino acid metabolism, and pyrimidine metabolism. Additionally, glycolysis and the Wood-Werkman cycle were inhibited in CCSM0331 but enhanced in ATCC6919. The expression of genes involved in porphyrin metabolism, associated with inflammation, was significantly reduced.

CONCLUSIONS

Phenoxyethanol exhibits the antimicrobial activity against C. acnes, with differential effects on phylotypes, targeting critical metabolic pathways and cellular processes. These findings indicate its potential for acne treatment.

Antioxidant Activities of the Cell-Free Supernatant of a Potential Probiotic Cutibacterium acnes Strain CCSM0331, Isolated From a Healthy Skin

OBJECTIVE

Oxidative stress activates the reactive oxygen species (ROS) and excessive ROS can damage skin cells, initiating oxidative stress responses that contribute to inflammation, aging, and other skin issues. As a resident skin bacterium, Cutibacterium acnes (C. acnes) plays an important role in maintaining skin homeostasis and provides antioxidant benefits. However, the metabolite components and mechanisms of C. acnes exerting antioxidant activity are not yet clear. This study aimed to analyze the potential antioxidant effects of C. acnes cell-free supernatant and the mechanisms.

METHODS

The antioxidant effects were evaluated by measuring the scavenging activities of 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid ammonium salt) (ABTS) radicals, and hydroxyl radicals, as well as the effects on ROS levels in menadione-induced primary human keratinocytes in vitro. Additionally, western blot analysis was performed to assess the antioxidant effects of the C. acnes CCSM0331 cell-free supernatant (CFS).

RESULTS

C. acnes CCSM0331 was isolated from the facial skin of healthy individuals. This strain, classified as type II, is associated with healthy skin. The CFS of strain CCSM0331 contained various short-chain fatty acids (SCFAs), glutathione peroxidase (GSH-Px), and total superoxide dismutase(T-SOD), exhibiting strong DPPH and ABTS radical scavenging capabilities, thus demonstrating substantial antioxidant activity. In a reactive oxygen species model induced by menadione in primary human keratinocytes, the addition of 5% of the fermentation supernatant from this strain significantly reduced ROS levels, indicating a notable ROS-scavenging effect. Western blot analysis further confirmed that the CCSM0331 fermentation supernatant activated the expression of Nrf-2 and HO-1 proteins, thereby activating the Nrf-2 oxidative stress pathway and exerting antioxidant effects.

CONCLUSION

C. acnes CCSM0331 is a promising skin probiotic with notable antioxidant properties. The activity of this strain exhibited significant free radical scavenging activity, suggesting its potential application in the development of antiaging products. This study provides theoretical support for the screening of functional skin bacteria or skin probiotics.

Novel anti-oxidative peptides from equine hemoplasma protein hydrolysates: Purification, identification and protective effects on Caco-2 cells

In this study, we purified and identified antioxidant peptides from equine plasma protein hydrolysates and assessed their protective effects against H2O2-induced oxidative stress in Caco-2 cells. Four antioxidant peptides were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS) in equine plasma protein hydrolysate, namely: GTMVGC (567.69 Da), FGMTST (662.88 Da), VGYHSHF (847.01 Da) and ALSPFFKE (939.18 Da). Among them, ALSPFFKE showed the strongest antidigestive properties after modelled digestion studies. Moreover, ALSPFFKE enhanced intracellular superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) activities while significantly reducing reactive oxygen species accumulation and malondialdehyde formation in Caco-2 cells. The molecular docking analysis suggested that ALSPFFKE achieves regulation of the Keap1-Nrf2 pathway mainly by forming multiple hydrogen bonds and hydrophobic interactions with key amino acids (Arg380, Ser555, Gln530, Tyr334) in Keap1. These findings suggested that equine plasma peptides hold significant promise for the development of novel, potent, and stable antioxidant functional foods.

Recent advances in cold plasma technology for enhancing the safety and quality of meat and meat products: A comprehensive review

Meat and meat products constitute an important component of the diet for several populations around the world and fulfill various nutritional requirements of the human body. However, owing to the inherent characteristics of meat - including its susceptibility to oxidation and contamination with foodborne pathogens - meat and meat products perish easily. In recent years, with improvements in living standards and increased focus on nutrition and health among consumers, non-thermal food processing technologies have received increasing attention. Among these strategies, cold plasma (CP) technology has emerged as a promising and novel processing technique with substantial potential in preserving meat and meat products. In this review, we discussed and analyzed the effects of CP on the nutritional value, sensory quality, and safety of meat and meat products, particularly, the potential toxicological hazards. Furthermore, we provided a detailed introduction to the mechanisms about how CP affects microorganisms, highlighting its role in inducing apoptosis and inhibiting quorum sensing. In the base of these theoretical foundations, this paper proposed several practical recommendations in order to optimize CP technology. Finally, we summarized the potential applications of CP in meat preservation, aiming to establish a theoretical framework for further research and application of this technology.

The correlation between Smac, IAPs and mitochondrial apoptosis, muscle tenderness during postmortem aging of Oula Tibetan sheep meat

Oula Tibetan sheep meat has rich nutritional value but relatively poor tenderness. Recently, apoptosis of muscle cells has gradually become a research hotspot for improving meat tenderness during postmortem aging. Smac can promote the decrease of IAPs expression in tumor cells, thereby inducing mitochondrial apoptosis. However, the relationship between Smac, IAPs and mitochondrial apoptosis, muscle tenderness during postmortem meat aging is still unclear. Thus, the aim of this work was to explore the relationship between Smac, IAPs and mitochondrial apoptosis as well as muscle tenderness during postmortem meat aging. Smac concentration, IAPs concentration, pH value, ATP content, SDH activity, MPTP opening degree, MMP, caspase-3/9 activity, apoptotic rate, MFI and shear force value of Oula Tibetan sheep meat were measured at different aging times and correlation analysis was performed. Correlation analysis revealed that Smac, IAPs were markedly related to mitochondrial apoptosis and muscle tenderness during postmortem aging of Tibetan sheep meat. The results suggest that Smac may regulate IAPs to promote mitochondrial apoptosis and muscle tenderization in Oula Tibetan sheep meat during postmortem aging.

Effect of plasma-activated lactic acid on microbiota composition and quality of puffer fish (Takifugu obscurus) fillets during chilled storage

Fresh puffer fish (Takifugu obscurus) are susceptible to microbial contamination and have a very short shelf-life of chilled storage. Hence, this study aimed to evaluate the effects of plasma-activated lactic acid (PALA) on microbiota composition and quality attributes of puffer fish fillets during chilled storage. The results showed that PALA treatment effectively reduced the growth of bacteria and attenuated changes in physicochemical indicators (total volatile basic nitrogen, pH value, K value, and biogenic amines) of puffer fish fillets. Additionally, insignificant changes were observed in lipid oxidation during the first 8 days (p > 0.05). Illumina-MiSeq high-throughput sequencing revealed that PALA effectively inhibited the growth of Pseudomonas in puffer fish fillets and maintained the diverse characteristics of the microbial community. In combination with sensory analysis, PALA extended the shelf life of puffer fish fillets for 4 days, suggesting that PALA could be considered a potential fish fillet preservation method.

Antibacterial efficacy of phenyllactic acid against Pseudomonas lundensis and Brochothrix thermosphacta and its synergistic application on modified atmosphere/air-packaged fresh pork loins

Microbial contamination is a crucial problem that is difficult to solve for the meat industry. Therefore, this study explored the antibacterial efficacy of phenyllactic acid (PLA) against Pseudomonas lundensis (PL) and Brochothrix thermosphacta (BT) solely and in combination (PL + BT). It also provided insights into its synergistic preservation effect during inoculation in chilled (4 °C) fresh pork loins under air (AP) and modified atmosphere packaging (MAP). The minimum inhibitory concentration (MIC) of PLA was 10 mg/mL. Growth kinetics, scanning electron microscopy (SEM), zeta potential, and cell viability investigations showed that PLA treatment exhibited reduced bacterial growth, aided morphological alterations, and leakage in cell membrane integrity in vitro. Nonetheless, PLA and MAP (70 %N2/30 %CO2) showed an excellent synergistic antibacterial ability against spoilage indicators(total glucose, pH, TVB-N, and TBARS), bacterial counts than AP, without impairing organoleptic acceptability. These results demonstrate the broad antibacterial efficacy of PLA as a biopreservative for the meat industry.