Heptanal inhibits the growth of Aspergillus flavus through disturbance of plasma membrane integrity, mitochondrial function and antioxidant enzyme activity

Antifungal mechanisms of phenyllactic acid against Mucor racemosus: Insights from spore growth suppression, and proteomic analysis

Mucor, a common mold, is a major cause of post-harvest spoilage in sweet cherries, leading to significant economic losses. While previous studies have demonstrated that phenyllactic acid (PLA) exhibits potent antifungal activity against Mucor, its underlying mechanism remains unclear. Here, we probed into the efficacy of PLA in inhibiting Mucor spore growth and explored its mechanisms of action. PLA treatment suppressed Mucor spore growth in a dose-dependent manner, with a minimum inhibitory concentration of 12 mmol/L. Morphological analysis revealed that PLA caused nuclear chromatin condensation, DNA fragmentation, and severe ultrastructural damage, including cell swelling, vacuolization, and separation of the cell wall from the membrane. Additionally, results of flow cytometry showed that PLA induced phosphatidylserine externalization, mitochondrial membrane potential depolarization, and intracellular reactive oxygen species accumulation in Mucor spore cells. Tandem Mass Tag (TMT)-based proteomic analysis identified 1248 differentially expressed proteins (DEPs; 616 upregulated and 632 downregulated) in Mucor spores treated with 24 mmol/L PLA, compared to the untreated control (p < 0.05). Bioinformatics analysis revealed that these DEPs were primarily involved in oxidative phosphorylation, glycolysis, the citrate cycle, and the biosynthesis and metabolism of carbon and amino acids. Overall, these findings elucidate the antifungal mechanisms of PLA against Mucor spores and provide valuable insights into the potential application of PLA in food preservation.

Traceability and discrimination of opium poppy shell analogues using HS-GC-IMS combined with machine learning algorithms

Illegal adulteration has been a critical issue in food safety, emerging as a focal point in forensic science. This situation has led to an increased demand for effective detection and monitoring technologies. Opium poppy shells are a critical source of drugs, and the accurate tracing and identification of their analogues are essential in drug-related cases. The features of volatile compounds in six opium poppy shell analogues (OPSA) were characterized using headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) in this study, and an accurate model for origin tracing was established through the integration of machine learning algorithms. A total of 213 volatile compounds were accurately identified, with esters, ketones, aldehydes, alcohols, and alkenes being the most abundant compounds. Additionally, two supervised machine learning algorithm classification models were established based on the HS-GC-IMS dataset to predict the categories of OPSA, including the orthogonal partial least squares discriminant analysis (OPLS-DA) and random forest models, and were subsequently compared with unsupervised models. By employing the random forest classification model, significant volatile compound characteristics were recognized, resulting in enhanced efficiency. Furthermore, the model achieved an out-of-bag (OOB) error value of 0, indicating excellent predictive capability for tracing and distinguishing OPSA. Our research findings indicate that the integration of HS-GC-IMS with machine learning is expected to enhance the efficiency and accuracy of tracing and identifying the categories of OPSA, thereby providing theoretical support for litigation and judicial processes.

Plasma and urine metabolomics for the identification of diagnostic biomarkers for sulfur mustard-induced lung injury

BACKGROUND

Sulfur mustard (SM) is a highly lethal chemical warfare agent that induces severe health complications in exposed individuals. Gaining insights into the metabolic changes caused by SM exposure is essential for understanding its underlying mechanisms and developing effective diagnostic and therapeutic interventions.

METHODS

In this investigation, we utilized proton nuclear magnetic resonance (H-NMR) spectroscopy to conduct metabolomic analysis in patients diagnosed with mustard lung disease (MLD) using a non-targeted approach. Metabolite measurements were conducted on plasma and urine samples collected from a total of 54 individuals, including 20 individuals with mild MLD, 20 individuals with moderate MLD, and 14 healthy individuals. Multivariate and univariate analyses were applied to identify metabolites that distinguish between the different groups, and enrichment analysis was performed to unveil the underlying biochemical pathways involved.

RESULTS

The obtained metabolic profile had the potential to differentiate moderate from healthy plasma, but not from mild patients using multivariate analysis. Sixteen metabolites from plasma were considered significantly different between the moderate and control groups (VIP > 1 and p < 0.05) that these metabolites involved in fatty acid and amino acid metabolism. Utilizing all 16 metabolites as a combined panel, we were able to distinguish between the moderate and control groups, achieving an area under the curve (AUC) of 0.854. Moreover, 6 and 8 urinary metabolites were detected between mild vs. control and moderate vs. control groups, respectively. Fourteen metabolites exhibited significant fold changes (FC) (FC < 0.66 or FC > 1.5; p < 0.05). These metabolites are involved in amino acid and nicotinate metabolism.

CONCLUSION

Our study provides novel insights into the metabolic changes associated with MLD and highlights potential pathways involved in the disease progression. These findings have implications for the development of targeted diagnostic and therapeutic strategies for MLD.

Cocoa Pod Husk Valorization Through Rhizopus stolonifer Solid-State Fermentation: Enhancement in Antioxidant Activity

Cocoa pod husk (CPH), a significant agricultural byproduct of cocoa production, presents an opportunity for sustainable valorization through biotechnological methods. This study aimed to enhance the nutritional, antioxidant, and therapeutic properties of CPH using solid-state fermentation (SSF) with Rhizopus stolonifer. Physicochemical characterization confirmed CPH's suitability for SSF, providing a nutrient-rich and favorable environment for fungal growth. The fermentation process significantly improved protein recovery (11.327 ± 0.859 mg g-1) and antioxidant activity, with ORAC (51.68 ± 0.35 mmol TE g-1) and DPPH (7.09 ± 0.05 µmol TE g-1) assays demonstrating marked increases in redox potential, particularly at 144 h and 96 h of fermentation, respectively. GC-MS analysis revealed the generation of bioactive compounds in fermented CPH (CPHF), including methyl 3-hydroxybutyrate, 10,12-Tricosadiynoic acid, and palmitic acid, which are known for their antioxidant, anti-inflammatory, and therapeutic properties. Additionally, phenolic compounds are biotransformed into more bioavailable forms, further enhancing the functional value of the material. This work demonstrates that SSF can effectively transform CPH from an agricultural waste product into a high-value biomaterial with potential applications in functional food, nutraceutical, and pharmaceutical industries. By addressing waste management challenges and promoting the development of innovative bio-based products, this study highlights the promising role of SSF in advancing sustainable and circular biotechnological solutions.

Peppermint Essential Oil For Controlling Aspergillus flavus and Analysis of its Antifungal Action Mode

Aspergillus flavus contamination has long been a major problem in the food and agriculture industries, while peppermint essential oil (PEO) is increasingly recognized as an effective alternative for controlling fungal spoilage. However, its biocontrol effect and action mode on A. flavus have rarely been reported. Here, the inhibition rates of PEO on A. flavus were determined by the plate fumigation and mycelial dry weight method. The minimum inhibitory concentration (MIC) was identified as 0.343 μL/mL. In the biocontrol tests, the moldy rates of maize kernels, wheat grains, and peanut kernels in the PEO treatment group were significantly reduced by 65%, 72%, and 63.33%, respectively. The biocontrol efficacy of PEO on maize kernels, wheat grains, and peanut kernels reached 80.67%, 82%, and 67.67%, respectively. Furthermore, antifungal action mode analysis showed that PEO changed the mycelial morphology, damaged the integrity of cell wall and membrane. Moreover, it reduced the ergosterol content, elevated the malondialdehyde content, increased the relative conductivity, and led to the intracellular leakage of nucleic acids and proteins, thereby enhancing the cell membrane permeability. In addition, PEO decreased the antioxidant-related catalase (CAT) and superoxide dismutase (SOD) activities, significantly increased the hydrogen peroxide (H2O2) content, and induced the accumulation of reactive oxygen species (ROS) in the mycelia. In conclusion, this study confirms that PEO, as an effective natural antimicrobial agent, has good application prospects in controlling the spoilage of A. flavus during grain storage and preventing food mold.

Antifungal Effects and Postharvest Diseases Control Potential of E, E-2, 4-Nonadienal against Rhizopus stolonifer

Pathogenic microorganisms are a significant cause of food spoilage, adversely affecting both product quality and human health. This study evaluated the antifungal activities of 34 aldehydes against foodborne and plant pathogenic fungi, identifying 8 promising lead compounds. Among them, E, E-2, 4-nonadienal exhibited optimal effects against Rhizopus stolonifer with an EC50 of 11.29 μg/mL. In vitro assays demonstrated that E, E-2, 4-nonadienal significantly impact R. stolonifer through both direct contact and fumigation. The preliminary mode of action (MOA) studies indicated that it effectively inhibited spore germination, disrupted ergosterol biosynthesis, and induced oxidative stress, affecting the permeability of the fungal cell membrane and altering mycelial morphology. Additionally, E, E-2, 4-nonadienal significantly reduced soft rot in spore-infected stored cherry tomatoes and showed low toxicity. Thus, aldehydes, exemplified by E, E-2, 4-nonadienal, are potential food and agricultural preservatives, offering efficiency, safety, and cost-effectiveness.

Volatile Organic Compounds Produced by Bacillus sp. Strain R2 Inhibit Aspergillus flavus Growth In Vitro and in Unhulled Rice

Volatile organic compounds (VOCs) produced by Bacillus species exhibit biocontrol activity against fungal pathogens of fruits and vegetables. However, research on the effect of VOCs on Aspergillus flavus in stored grains is limited. This study aimed to investigate the effects of VOCs extracted from the strain R2, which was isolated from unhulled rice and identified as Bacillus paramycoides on A. flavus in vitro and unhulled rice. R2 VOCs effectively inhibited conidial germination and the hyphal growth of A. flavus in vitro. Moreover, R2 VOCs reduced the fungal population, aflatoxin B1 (AFB1) levels, and free fatty acid (FFA) value by 90.8%, 67%, and 38.7%, respectively, in unhulled rice. Eighteen R2 VOCs were identified using headspace solid-phase micro-extraction gas chromatography-mass spectrometry, and the individual activity of the VOCs against A. flavus was tested in vitro. Benzaldehyde (Ben) and 3,7-dimethyl-1-octanol (Dmo) showed strong inhibitory activities against A. flavus on PDA plates, with inhibition rates of 100% and 91.2%, respectively, at a concentration of 20 μL/dish. Ben at the concentration of 0.09 mg/mL, Dmo at the concentration of 0.07 mg/mL, or a mixture of both at halved concentrations could reduce the fungal population, AFB1 levels, and FFA content in unhulled rice. Our findings suggest that R2 VOCs are good alternatives to traditional chemical fumigants for suppressing A. flavus in stored grains. However, further research is necessary to establish the optimal fumigation concentration of these two components in unhulled rice. The impact of their residues on grain quality should be explored through sensory evaluation and nutritional analysis, and their safety to the environment and human body should be evaluated through safety assessment.

D-Limonene Inhibits Pichia kluyveri Y-11519 in Sichuan Pickles by Disrupting Metabolism

The Pichia kluyveri, a proliferation commonly found in Sichuan pickles (SCPs), can accelerate the growth and reproduction of spoilage bacteria, causing off-odor development and decay. Although D-limonene, a common natural preservative, effectively restricts P. kluyveri, its inhibitory mechanism remains unclear. This study aimed to elucidate this molecular mechanism by investigating the impact on basic P. kluyveri metabolism. The findings revealed that D-limonene inhibited P. kluyveri growth and disrupted the transcription of the genes responsible for encoding the enzymes involved in cell wall and membrane synthesis, oxidative phosphorylation, glycolysis, and the tricarboxylic acid (TCA) cycle pathway. The results indicated that these events disrupted crucial metabolism such as cell wall and membrane integrity, adenosine triphosphate (ATP) synthesis, and reactive oxygen species (ROS) balance. These insights provided a comprehensive understanding of the inhibitory effect of D-limonene on the growth and reproduction of P. kluyveri while highlighting its potential application in the SCP industry.

Mechanisms of methyl 2-methylbutyrate suppression on Aspergillus flavus growth and aflatoxin B1 biosynthesis

Aspergillus flavus and subsequently produced carcinogenic aflatoxins frequently contaminate postharvest food crops, resulting in a threat to global food safety. Chemical preservatives are currently the main antifungal agents. However, fungal resistance effect, biological toxicity, and environmental contamination limit their practical applications. The application of natural volatile organic compounds has great potential for controlling fungal and mycotoxin contamination of postharvest food crops. This study therefore investigated the antifungal and anti-aflatoxigenic activities of the volatile compound, methyl 2-methylbutyrate (M2M), against Aspergillus flavus and its potential mechanisms. M2M effectively inhibited A. flavus mycelia growth, with a minimum inhibitory concentration of 2.0 μL/mL. Moreover, M2M also suppressed aflatoxin production, sclerotia production, and the pathogenicity on peanut and corn flour. RNA-Seq results showed that 2899 differentially expressed genes (DEGs), and DEGs involved in ergosterol synthesis, cell wall structure, glycolysis, citric acid cycle, mitogen activated protein kinase signaling pathway, DNA replication, and aflatoxin biosynthesis, were down-regulated in A. flavus. Further studies showed that M2M strongly damaged the cell membrane and cell wall integrity, reduced ATP levels, and induced reactive oxygen species (ROS) accumulation and DNA damage. Notably, a GATA type zinc finger transcription factor, AfSreA (AFLA_132440), which is essential for A. flavus growth and aflatoxin production, was identified. The growth and aflatoxin yield in the ΔAfSreA strain decreased by 94.94 % and 71.82 %, respectively. Additionally, deletion of AfSreA destroyed cell wall integrity and decreased expressions of genes involved in aflatoxin biosynthesis. Taken together, our results identified the antifungal and anti-aflatoxigenic mechanisms of M2M against A. flavus, and confirmed the potential of M2M in protecting peanut and corn from fungal contamination.

Correlation between microbial communities and volatile organic compounds in an urban soil provides clues on soil quality towards sustainability of city flowerbeds

Soil functionality is critical to the biosphere as it provides ecosystem services relevant for a healthy planet. The soil microbial composition is significantly impacted by anthropogenic activities, including urbanization. In this context, the study of soil microorganisms associated to urban green spaces has started to be crucial toward sustainable city development. Microbes living in the soil produce and degrade volatile organic compounds (VOCs). The VOC profiles may be used to distinguish between soils with various characteristics and management practices, reflecting variations in the activity of soil microbes that use a variety of metabolic pathways. Here, a combined approach based on DNA metabarcoding and GC-MS analysis was used to evaluate the soil quality from urban flowerbeds in Prato (Tuscany, Italy) in terms of microbial biodiversity and VOC emission profiles, with the final aim of evaluating the possible correlation between composition of microbial community and VOC patterns. Results showed that VOCs in the considered soil originated from anthropic and biological activity, and significant correlations between specific microbial taxa and VOCs were detected. Overall, the study demonstrated the feasibility of the use of microbe-VOC correlation as a proxy for soil quality assessment in urban soils.

Protection of postharvest grains from fungal spoilage by biogenic volatiles

Fungal spoilage of postharvest grains poses serious problems with respect to food safety, human health, and the economic value of grains. The protection of cereal grains from deleterious fungi is a critical aim in postharvest grain management. Considering the bulk volume of grain piles in warehouses or bins and food safety, fumigation with natural gaseous fungicides is a promising strategy to control fungal contamination on postharvest grains. Increasing research has focused on the antifungal properties of biogenic volatiles. This review summarizes the literature related to the effects of biogenic volatiles from microbes and plants on spoilage fungi on postharvest grains and highlights the underlying antifungal mechanisms. Key areas for additional research on fumigation with biogenic volatiles in postharvest grains are noted. The research described in this review supports the protective effects of biogenic volatiles against grain spoilage by fungi, providing a basis for their expanded application in the management of postharvest grains.

Variation with In Vitro Analysis of Volatile Profiles among Aspergillus flavus Strains from Louisiana

Volatile organic compounds (VOCs) produced by A. flavus strains were first captured and identified to discern between non-aflatoxigenic and toxigenic phenotypes, and more recently to help with detecting fungal infection, but not with the goal of using VOCs produced by non-aflatoxigenic strains to inhibit growth and/or production of one or more mycotoxins (e.g., aflatoxin and cyclopiazonic acid) by toxigenic aspergilli. In this study, four Aspergillus strains from Louisiana (one non-aflatoxigenic and three toxigenic) were grown on various substrates and had their headspaces captured and analyzed by solid-phase microextraction/gas chromatography/mass spectroscopy (SPME/GC/MS), to find biocontrol and biomarker compounds. Here, we present a collection of nearly 100 fungus-related VOCs, many of which were substrate dependent. Thirty-one were produced across multiple replicates and the rest were observed in a single replicate. At least three VOCs unique to non-aflatoxigenic strain LA1 can be tested for biocontrol properties (e.g., euparone, 4-nonyne), and at least four VOCs unique to toxigenic strains LA2-LA4 can be explored as biomarkers (e.g., 2-heptanone, glycocyamidine) to detect their presence while infecting crops in the field or in storage.

Inhibitory effect of (E)-2-heptenal on Aspergillus flavus growth revealed by metabolomics and biochemical analyses

The prevention of fungal proliferation in postharvest grains is critical for maintaining grain quality and reducing mycotoxin contamination. Fumigation with natural gaseous fungicides is a promising and sustainable approach to protect grains from fungal spoilage. In this study, the antifungal activities of (E)-2-alkenals (C₅-C₁₀) on Aspergillus flavus were tested in the vapor phase, and (E)-2-heptenal showed the highest antifungal activity against A. flavus. (E)-2-Heptenal completely inhibited A. flavus growth at 0.0125 µL/mL and 0.2 µL/mL in the vapor phase and liquid contact, respectively. (E)-2-Heptenal can disrupt the plasma membrane integrity of A. flavus via leakage of intracellular electrolytes. Scanning electron microscopy indicated that the mycelial morphology of A. flavus was remarkably affected by (E)-2-heptenal. Metabolomic analyses indicated that 49 metabolites were significantly differentially expressed in A. flavus mycelia exposed to 0.2 µL/mL (E)-2-heptenal; these metabolites were mainly involved in galactose metabolism, starch and sucrose metabolism, the phosphotransferase system, and ATP-binding cassette transporters. ATP production was reduced in (E)-2-heptenal-treated A. flavus, and Janus Green B staining showed reduced cytochrome c oxidase activity. (E)-2-Heptenal treatment induced oxidative stress in A. flavus mycelia with an accumulation of superoxide anions and hydrogen peroxide and increased activities of superoxide dismutase and catalase. Simulated storage experiments showed that fumigation with 400 µL/L of (E)-2-heptenal vapor could completely inhibit A. flavus growth in wheat grains with 20% moisture; this demonstrates its potential use in preventing grain spoilage. This study provides valuable insights into understanding the antifungal effects of (E)-2-heptenal on A. flavus. KEY POINTS : • (E)-2-Heptenal vapor showed the highest antifungal activity against A. flavus among (C₅-C₁₀) (E)-2-alkenals. • The antifungal effects of (E)-2-heptenal against A. flavus were determined. • The antifungal actions of (E)-2-heptenal on A. flavus were revealed by metabolomics and biochemical analyses.

Natural Compounds in the Battle against Microorganisms-Linalool

The purpose of this article is to present recent studies on the antimicrobial properties of linalool, the mechanism of action on cells and detoxification processes. The current trend of employing compounds present in essential oils to support antibiotic therapy is becoming increasingly popular. Naturally occurring monoterpene constituents of essential oils are undergoing detailed studies to understand their detailed effects on the human body, both independently and in doses correlated with currently used pharmaceuticals. One such compound is linalool, which is commonly found in many herbs and is used to flavor black tea. This compound is an excellent fragrance additive for cosmetics, enhancing the preservative effect of the formulations used in them or acting as an anti-inflammatory on mild skin lesions. Previous studies have shown that it is extremely important due to its broad spectrum of biological activities, i.e., antioxidant, anti-inflammatory, anticancer, cardioprotective and antimicrobial. Among opportunistic hospital strains, it is most active against Gram-negative bacteria. The mechanism of action of linalool against microorganisms is still under intensive investigation. One of the key aspects of linalool research is biotransformation, through which its susceptibility to detoxification processes is determined.

The antifungal mechanisms of plant volatile compound 1-octanol against Aspergillus flavus growth

The exploitation of active ingredients from plant volatile organic compounds as natural gaseous fungicides shows remarkable potential for controlling fungal decay in postharvest agroproducts. Although 1-octanol is a common component of cereal volatiles, its antifungal potency against spoilage fungi in postharvest grains remains unclear. In this study, we studied the effectiveness of 1-octanol against Aspergillus flavus growth in postharvest grains and its mechanisms of action. 1-Octanol vapor and liquid contact dose-dependently inhibited A. flavus spore germination and mycelial growth at a low concentration. The simulated storage experiment demonstrated that 300 μL/L of 1-octanol vapor completely controlled A. flavus growth in wheat, corn, and paddy grains with 20% moisture content. 1-Octanol treatment irreversibly damaged the conidial and mycelial morphology of A. flavus and caused electrolyte leakage due to reduced plasma membrane integrity. It induced apoptosis along with morphological abnormalities, phosphatidylserine externalization, mitochondrial membrane potential depolarization, intracellular reactive oxygen species accumulation, and DNA fragmentation in A. flavus cells. Metabolomic analysis revealed that 1-octanol treatment disrupted the biosynthesis of unsaturated fatty acids, ATP-binding cassette transporters, amino acid metabolism, and glycerophospholipid metabolism. This study demonstrated the promising application potential of 1-octanol as a biofumigant for preventing fungal spoilage of postharvest cereal grains. KEY POINTS: • (1) 1-Octanol inhibits Aspergillus flavus growth in the vapor phase and liquid contact; • (2) 1-Octanol damages membrane integrity and induces apoptosis of A. flavus; • (3) Metabolomic changes in A. flavus mycelia were analyzed after 1-octanol treatment.