Flavus Spores Research Articles

Curcumin-Based Photosensitization, a Green Treatment in Inactivating Aspergillus flavus Spores in Peanuts.

Controlling microbial contamination in foods using effective clean and green technologies is important in producing food with less contaminants. This study investigates the effect of photosensitization treatment using naturally occurring curcumin on inactivating Aspergillus flavus spores on peanuts. Light dosages of 76.4 J/cm2 and 114.5 J/cm2 at 420 nm were employed in combination with curcumin concentrations from 25 to 100 μM. The inactivation efficiency of the treatment towards spores in suspension achieved a maximum 2 log CFU/mL reduction in viable spores with 75 μM of curcumin at a light dosage of 114.5 J/cm2 (p < 0.05). The in vivo study was then designed using the optimum conditions from the in vitro experiment. The photosensitization treatment at three different curcumin concentrations (50, 75, 100 μM) extended the shelf-life of raw peanuts by 7 days when treated with 75 μM of curcumin combined with a 114.5 J/cm2 light dosage and stored at 25 °C. The treatment effectively reduced average levels of aflatoxin B1 (AF-B1) on peanuts stored for 7 days at 25 °C from 9.65 mg/kg of untreated samples to 0.007 and 0.006 mg/kg for 75 and 100 μM curcumin (p < 0.05) respectively. The results show the potential use of curcumin-based photosensitization treatment in inactivating fungal growth and reducing AF-B1 concentration on raw peanuts.

Transcriptome analysis reveals the underlying mechanism of heptanal against Aspergillus flavus spore germination.

Methods of controlling Aspergillus flavus contamination in agro-products have attracted attention because of its impact on global food security. We previously reported that the natural cereal volatile heptanal could effectively inhibit A. flavus growth and showed great potential as a bio-preservative agent. In this study, the minimum inhibitory concentration and minimum fungicide concentration of heptanal could change the surface morphology of A. flavus spores, causing them to wrinkle and collapse. Transcriptomic analysis showed that heptanal treatment significantly changed the expression of several genes involved in cell wall and plasma damage, reactive oxygen species (ROS) accumulation, energy metabolism, AMPK-activated protein kinase, biosynthesis of unsaturated fatty acids, RNA degradation, and DNA replication. Heptanal-induced early apoptosis of A. flavus spores was characterized by decreased mitochondrial membrane potential, increased intracellular ROS production, and DNA fragmentation. This study provides new insight into the inhibitory mechanism of heptanal against A. flavus and points to its potential application as a bio-preservative. KEY POINTS: • Heptanal can effectively inhibit A. flavus growth in cereal grains. • The transcriptional changes in A. flavus spores exposed to heptanal were analyzed. • The antifungal mechanism of heptanal against A. flavus was elucidated.

Expression of immune response genes in human corneal epithelial cells interacting with Aspergillus flavus conidia

BackgroundAspergillus flavus, one of the causative agents of human fungal keratitis, can be phagocytosed by human corneal epithelial (HCE) cells and the conidia containing phagosomes mature into phagolysosomes. But the immunological responses of human corneal epithelial cells interacting with A. flavus are not clear. In this study, we report the expression of immune response related genes of HCE cells exposed to A. flavus spores using targeted transcriptomics.MethodsHuman corneal epithelial cell line and primary cultures were grown in a six-well plate and used for coculture experiments. Internalization of the conidia was confirmed by immunofluorescence microscopy of the colocalized endosomal markers CD71 and LAMP1. Total RNA was isolated, and the quantity and quality of the isolated RNA were assessed using Qubit and Bioanalyzer. NanoString nCounter platform was used for the analysis of mRNA abundance using the Human Immunology panel. R-package and nSolver software were used for data analysis. KEGG and FunRich 3.1.3 tools were used to analyze the differentially expressed genes.ResultsDifferent morphotypes of conidia were observed after 6 h of coculture with human corneal epithelial cells and found to be internalized by epithelial cells. NanoString profiling showed more than 20 differentially expressed genes in immortalized human corneal epithelial cell line and more than ten differentially expressed genes in primary corneal epithelial cells. Distinct set of genes were altered in their expression in cell line and primary corneal epithelial cells. KEGG pathway analysis revealed that genes associated with TNF signaling, NF-KB signaling, and Th17 signaling were up-regulated, and genes associated with chemokine signaling and B cell receptor signaling were down regulated. FunRich pathway analysis showed that pathways such as CDC42 signaling, PI3K signaling, and Arf6 trafficking events were activated by the clinical isolates CI1123 and CI1698 in both type of cells.ConclusionsCombining the transcript analysis data from cell lines and primary cultures, we showed the up regulation of immune defense genes in A. flavus infected cells. At the same time, chemokine signaling and B cell signaling pathways are downregulated. The variability in the expression levels in the immortalized cell line and the primary cultures is likely due to the variable epigenetic reprogramming in the immortalized cells and primary cultures in the absence of any changes in the genome. It highlights the importance of using both cell types in host-pathogen interaction studies.

Spatial and Temporal Population Dynamics of Aspergillus flavus in Commercial Pistachio Orchards in Arizona

Aspergillus flavus infects a wide range of crops, including pistachio, and subsequent aflatoxin contamination results in significant economic losses. Application of biocontrol products based on nonaflatoxigenic (atoxigenic) strains of A. flavus is one of the most effective tactics for controlling aflatoxins in crops. Both risk of aflatoxin contamination and effectiveness of biocontrol are influenced by the extent to which A. flavus spores move into pistachio tree canopies during periods of nut development. Thus, the purpose of this study was to evaluate spatial and temporal population dynamics of A. flavus, including the applied biocontrol strain AF36, in canopies of pistachio orchards in Arizona. Propagule densities of A. flavus were quantified on leaf samples collected from lower, middle, and upper canopies from spring through harvest in 2018 and 2019. A. flavus propagule densities peaked during periods of high temperature and rainfall in 2018 (up to 600 CFU/g) and 2019 (up to 23 CFU/g), which coincided with nut development and maturation. The applied biocontrol strain AF36 was detected at all canopy heights but overall propagule densities were greater in the upper and middle canopy (mean = 70 CFU/g) compared with the lower canopy (mean = 47 CFU/g). Results suggest that June to August is the period during which A. flavus inoculum increases in Arizona pistachio orchards and, to most effectively displace aflatoxin-producing fungi in tree canopies, biocontrol applications should precede this period. In addition, this study demonstrates that soil-applied biocontrol strains can successfully disperse throughout the canopies of commercial tree nut orchards.

Pathological study of genitourinary invasion by Aspergillus flavus in male rats

Due to the widespread of A. flavus spores and the high risk of its mycotoxins in our environment, we investigated the pathological effects of A. flavus on genitourinary system in experimental rats using a whole sonicated antigen (WSA), and modified mycotoxin (mycotoxoid) in the immunization process. Fifty albino male rats were involved, subdivided into five group, each group of 10 male rats. Group one as a negative control received phosphate buffer saline, group two as a positive control received a challenge dose of 1×106 /0.5ml viable conidia/rat, while group three was immunized by a mixture of WSA and mycotoxoid, G4 was immunized by WSA alone, and G5 was immunized by mycotoxoid alone. The immunization was performed in two doses with 2 weeks interval. The results showed a high immune response (in group three G3) stimulated by the mixture (WSA and mycotoxoid), which revealed a significant increase in both IL-17 and IFN-γ. After experimental infection, the sero-analysis showed a significant increase in IL-17 and IFN-γ serum levels compared with the mixture-immunized group which showed no significant increases. In addition, the histopathologic sections illustrated severe chronic inflammation with a typical fungal granulomatous reaction in the prostate glands and kidneys compared with the WSA-immunized groups which showed mild histological reactions. Finally, we conclude that A. flavus is a serious opportunistic pathogen that can disseminate into genitourinary organs inducing severe pathologic lesions and even death. Moreover, we found that immunization by WSA and mycotoxoid can significantly reduce both immune and histopathological effects of A. flavus and its mycotoxins.

Effect of humidity on aflatoxin contamination for selected African leafy vegetables.

In this study, the aflatoxin contamination level of selected freshly harvested and dried African leafy vegetables was investigated after inoculation with Aspergillus flavus spores and incubation at 32%, 74%, 84%, and 96% static relative humidity. The study question was whether Aspergillus sp. growth on selected vegetables: Corchorus olitorius, Crotalaria ochroleuca, Vigna unguiculata, Solanum villosum, and Amaranthus blitum can produce aflatoxins. The experiment was replicated thrice and a control sample was included for each replicate. An Agilent 1260 Infinity HPLC system was used for analysis and we quantified the following aflatoxins; B1, B2, G1, and G2 in the selected vegetables. Our results show that aflatoxin B1, G1, and G2 were all present, with the B1 being prevalent. The contamination level increased with relative humidity increase for both freshly harvested and dried vegetables. However, the dried vegetables had a lower contamination level in comparison with freshly harvested. The findings affirm the importance of post-harvest crop preservation to avoid mycotoxin contamination. The vegetables can suffer aflatoxin contamination when exposed to high moisture and ambient temperature and drying is a suitable method of vegetable preservation.

Hexanal induces early apoptosis of Aspergillus flavus conidia by disrupting mitochondrial function and expression of key genes.

Aspergillus flavus is a notorious saprophytic fungus that compromises the quantity and quality of postharvest grains and produces carcinogenic aflatoxins. The natural compound hexanal disrupts cell membrane synthesis and mitochondrial function and induces apoptosis in A. flavus; here, we investigated the molecular mechanisms underlying these effects. The minimum inhibition and fungicidal concentration (MIC and MFC) of hexanal against A. flavus spores were 3.2 and 9.6 μL/mL, respectively. Hexanal exposure resulted in abnormal spore morphology and early spore apoptosis. These changes were accompanied by increased reactive oxygen species production, reduced mitochondrial membrane potential, and DNA fragmentation. Transcriptomic analysis revealed that hexanal treatment greatly altered the metabolism of A. flavus spores, including membrane permeability, mitochondrial function, energy metabolism, DNA replication, oxidative stress, and autophagy. This study provides novel insights into the mechanism underlying the antifungal activity of hexanal, suggesting that hexanal can be used an anti-A. flavus agent for agricultural applications. KEY POINTS: • Hexanal exposure resulted in abnormal spore morphology. • The apoptotic characteristics of A. flavus were induced after hexanal treatment. • Hexanal could change the expression of key A. flavus growth-related genes.

Effect of Photosensitization Mediated by Curcumin on Carotenoid and Aflatoxin Content in Different Maize Varieties

Mycotoxins are naturally occurring toxins produced by certain types of fungi that contaminate food and feed, posing serious health risks to human and livestock. This study evaluated the combination of blue light with curcumin to inactivate Aspergillus flavus spores, its effect on aflatoxin B1 (AFB1) production and maintaining carotenoid content in three maize varieties. The study was first conducted in vitro, and the spore suspensions (104 CFU·mL−1) were treated with four curcumin concentrations (25 and 50 µM in ethanol, 1000 and 1250 µM in propylene glycol) and illuminated at different light doses from 0 to 130.3 J·cm−2. The photoinactivation efficiency was light-dose dependent with the highest photoinactivation of 2.3 log CFU·mL−1 achieved using 1000 µM curcumin at 104.2 J·cm−2. Scanning electron microscopy revealed cell wall deformations as well as less density in photosensitized cells. Photosensitization of maize kernels gave rise to a complete reduction in the viability of A. flavus and therefore inhibition of AFB1 production, while no significant (p &gt; 0.05) effect was observed using either light or curcumin. Moreover, photosensitization did not affect the carotenoids in all the studied maize varieties. The results suggest that photosensitization is a green alternative preservation technique to decontaminate maize kernels and reduce consumer exposure to AFB1 without any effect on carotenoid content.

Biocontrol Activity of Bacillus megaterium BM344-1 against Toxigenic Fungi.

Mycotoxins are secondary metabolites of some fungal species and represent important contaminants of food and feed. This study aimed to explore the biological control activity of Bacillus megaterium BM344-1 volatile organic compounds (VOCs) on the growth and mycotoxin production of single representatives of the toxigenic species Aspergillus flavus, Aspergillus carbonarius, Penicillium verrucosum, and Fusarium verticillioides. In vitro co-incubation experiments indicated the P. verrucosum isolate as the most sensitive one, with a growth inhibition ratio of 66.7%, followed by A. flavus (29.4%) and F. verticillioides (18.2%). Exposure of A. flavus, P. verrucosum, and F. verticillioides to BM344-1 VOCs resulted in complete inhibition of aflatoxins (AFB1, AFG1, and AFG2), ochratoxin A, and fumonisin B1 (FB1) synthesis on artificial media, respectively. In vivo experiments on maize kernels showed 51% inhibition of fungal growth on ears simultaneously infected with A. flavus spores and exposed to BM344-1 volatiles. Likewise, AF synthesis by A. flavus was significantly (p < 0.05) inhibited (25.34 ± 6.72 μg/kg) by bacterial volatiles as compared to that in control maize ears (91.81 ± 29.10 μg/kg). Gas chromatography–tandem mass spectrometry-based analysis of headspace volatiles revealed hexadecanoic acid methyl ester (palmitic acid) and tetracosane as bioactive compounds in the BM344-1 volatilome. Bacterial volatiles have promising potential to control the growth and mycotoxin synthesis of toxigenic fungi and may present valuable aid in the efforts to warrant food and feed safety.

Human Corneal Epithelial Cells Internalize Aspergillus flavus Spores by Actin-Mediated Endocytosis.

Human corneal epithelial (HCE) cells play a significant role in the innate immune response by secreting cytokines and antimicrobial peptides when they encounter fungal pathogens. But the detailed mechanism of attachment and engulfment of the fungal conidia by HCE cells is not well understood. Here, we show the phagocytosis of Aspergillus flavus conidia by RCB2280 cells and primary HCE cultures using confocal microscopy and proteomic analysis of conidium-containing phagosomes. Phalloidin staining showed actin polymerization, leading to an actin ring around engulfed conidia. Cytochalasin D inhibited the actin-mediated endocytosis of the conidia. Immunolabeling of the early endosomal markers CD71 and early endosomal antigen (EEA1) and the late endosomal markers lysosome-associated membrane protein 1 (LAMP1), Rab7, and cathepsin G showed that endosomal proteins were recruited to the site of conidia and showed maturation of the conidium-containing phagosomes. Lysotracker red DND 99 labeling showed the acidification of the phagosomes containing conidia. Phagosome-specific proteome analysis confirmed the recruitment of various phagosomal and endosomal proteins to the conidium-containing phagosomes. These results show that the ocular surface epithelium contributes actively to antifungal defense by the phagocytosis of invading fungal conidia.

The effectiveness of Saccharomyces cerevisiae in inhibiting aflatoxin production and reducing the harmful effects of aflatoxin in ducklings

Sacharomyces cerevisiae isolates were obtained from baker's yeast, soil, fruit and identified with PCR. Twenty-seven isolates of S. cerevisiae were screened for capacity of inhibition of aflatoxin production of Aspergillus flavus (A. flavus) on coconut extract agar media (CEA). The results showed that the coculture method of S. cerevisiae isolates and aflatoxin producing A. flavus on CEA medium could be used for screening the strains that are able to antagonize aflatoxin-producing A. flavus. On ground corn medium, with the rate of 104 aflatoxin-producing A. flavus spores and 108 S. cerevisiae yeast cells/g, S. cerevisiae was able to reduce the amount of aflatoxin produced by A. flavus in corn. In an in vivo experiment, it was found that addition of 108 cells of S. cerevisiae to one kg of duck feed contaminated with 300 ppb aflatoxin from 1 to 10 days of age reduced adverse effects of aflatoxin on the liver and kidneys of ducks

Antifungal properties of recombinant Puroindoline B protein against aflatoxigenic Aspergillus flavus

Aspergillus flavus contamination is of great concern to food safety. Our previous studies demonstrated that recombinant Puroindoline B protein (rPINB) has an inhibitory effect on A. flavus mycelium development. However, fungal contamination often begins with spore germination within food shelf life. Here, rPINB was evaluated for its antifungal properties against A. flavus spores in vivo and in vitro. The results showed that rPINB could inhibit spore formation and aflatoxin B1 of A. flavus on maize. In vitro analysis revealed its dose-dependent antifungal effect on spore germination and germ tube growth of A. flavus. Scanning electron microscopy revealed that rPINB exposure altered spore morphology, indicating it damaged the cell wall. Transmission electron microscopy and the inhibition of ergosterol synthesis further revealed that rPINB exposure significantly damaged the cell membrane. The mitochondrial membrane potential decreased, and DNA fragments were scattered in the cytoplasm as detected using 5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidazolocarbocyanine iodide and 4′,6-diamidino-2-phenylindole staining. The direct antifungal activity of rPINB observed both in vivo and in vitro suggests that rPINB may be used to prevent fungal contamination of stored foods and agricultural products in the future.

Comparison of biological methods to control Aphis fabae Scopoli (Hemiptera: Aphididae) on kalanchoe crops in East Africa

Aphids cause considerable damage to numerous crops all over the world and insecticides are the main means of controlling them, despite their detrimental impacts on human and environmental health. This study assessed the effectiveness of the parasitoid Aphidius colemani Viereck (Hymenoptera: Braconidae), a mixture of predatory ladybird beetles, Hippodamia variegata Goeze, Chilocorus calvus Chiccl, and Cheilomenes propinqua Mulsant (Coleoptera: Coccinellidae), and an entomopathogenic strain of Aspergillus flavus Link (Eurotiales: Trichocomaceae), collected locally in Tanzania, to control Aphis fabae Scopoli (Hemiptera: Aphididae). After assessing the predation and parasitism rates of these natural enemies at different aphid densities in laboratory experiments, their ability to control aphids on kalanchoe was assessed in a greenhouse experiment over two seasons. The largest number of A. fabae parasitized or consumed in the laboratory was found at a density of 160 aphids per predator, or parasitoid. At that density, an adult female of A. colemani parasitized 114 A. fabae per day, on average, and adults of C. calvus, H. variegata, and C. propinqua consumed 75, 72, and 85 aphids per day, respectively. A. flavus spores applied at 1 × 107 spores ml−1 reduced the aphid population by 7.9 and 12.6 times within 10 days in the first and second seasons of the greenhouse experiments, respectively, as opposed to 2.8 and 2.5 times by releasing a mixture of the ladybirds at a rate of 5 adults/m2, and by 3.3 and 9.5 times by releasing A. colemani at a rate of 2 adults/m2. This study confirmed the potential of these locally collected bio-control agents for controlling A. fabae. However, use of the isolated A. flavus strain was undermined by its production of aflatoxin. Further research is therefore required to tap into the potential of a non-toxic strain of A. flavus and/or other entomopathogenic fungi.

In vitro antifungal activity of Desmodium intortum and D. uncinatum root extracts against growth of toxigenic Fusarium verticillioides and Aspergillus flavus

Maize grown under push-pull cropping system has been reported to contain lower concentrations of fumonisin and aflatoxin than maize monocrop. This study determined the inhibitory effect of desmodium root extracts on spore germination and radial growth of toxigenic Aspergillus flavus and Fusarium verticillioides. Aspergillus flavus and F. verticillioides were isolated from maize and soil and tested for ability to produce aflatoxin and fumonisin by inoculation on mycotoxin-free maize. Aflatoxin and fuminisin were detected and quantified by direct competitive ELISA. Desmodium roots were dried, ground to fine powder and extracted with methanol and dichloromethane and evaluated for anti-fungal activity by inhibition of spores of A. flavus and F. verticillioides potato dextrose agar (PDA) medium. Isolates of F. verticillioides produced up to 599,741 µg/kg fumonisin while isolates of A. flavus produced up to 199,184 µg/kg aflatoxin. Desmodium root extracts reduced germination of A. flavus spores and F. verticillioides by 9.6% and 43.8%, respectively and reduced their respective colony radial growth by 15% and 57%. The results suggested that desmodium roots contain chemical compounds that inhibit growth of A. flavus and F. verticillioides. This may explain the reduction in infection of maize with mycotoxin-producing fungi before harvest in push-pull cropping systems by reducing the pathogen inoculum in the soils. Determination of the active compounds in the root exudates is recommended

High voltage atmospheric cold plasma treatment inactivates Aspergillus flavus spores and deoxynivalenol toxin

Fungal contamination is a concern for the food industry. Fungal spores resist food sterilization treatments and produce mycotoxins that are toxic for animals and humans. Technologies that deactivate spores and toxins without impacting food quality are desirable. This study demonstrates the efficiency of a high voltage atmospheric cold plasma (HVACP) technology using air to generate reactive oxygen (ROS) and nitrogen (RNS) species for the degradation of Aspergillus flavus cultures and the deoxynivalenol (DON) mycotoxin. Optical emission and absorption spectroscopy demonstrate ionization of hydroxyl groups, atomic oxygen and nitrogen, and confirm production of ROS and RNS, e.g. O3, NO2, NO3, N2O4, and N2O5. Fungal cultures show a depletion in pigmentation and an ~50% spore inactivation after 1-min treatments. Treated spores show surface ablation and membrane degradation by scanning electron microscopy. Twenty-minute direct HVACP treatments of 100 μg of DON in one mL aqueous suspensions resulted in a greater than 99% reduction in DON structure and rescued over 80% of Caco-2 cell viability; however, the same treatment on 100 μg of powdered DON toxin only showed a 33% reduction in DON and only rescued 15% of cell viability. In summary, HVACP air treatment can inactivate both fungal spores and toxins in minutes.

Storage of fungi with rice (Oryza sativa)-PRH 10 and their influence on seed quality

Presence of fungi causing infestations deteriorates quality of husked and dehisced rice (Oryza sativa L.) seed. So, identifying storage conditions is crucial in food safety programs. Present study deals with isolation of fungi and their purification from rice to know the impact on seed storage quality. Four important fungi causing infestations viz. Aspergillus flavus, A. niger, Penicillium sp. and Fusarium sp. were isolated and characterized. Culture filtrate of fungi were studied on rice seed deterioration on the basis of seed germination percentage, root/shoot length, total carbohydrate, total protein content, α-amylase activity, lipoxygenase activity and storage proteins profiling by SDSPAGE. Maximum deterioration in rice seed was observed with A. flavus spores filtrate inoculated seeds followed by A. niger, Penicillium sp. and Fusarium sp., respectively. Enzyme activity of α-amylase and lipoxygenase were significantly increased with seed storage and their ageing.

Effects of cold plasma on wheat grain microbiome and antimicrobial efficacy against challenge pathogens and their resistance

The safety and quality of cereal grain supplies are adversely impacted by microbiological contamination, with novel interventions required to maximise whole grains safety and stability. The microbiological contaminants of wheat grains and the efficacy of Atmospheric Cold Plasma (ACP) for potential to control these risks were investigated. The evaluations were performed using a contained reactor dielectric barrier discharge (DBD) system; samples were treated for 0–20 min using direct and indirect plasma exposure. Amplicon-based metagenomic analysis using bacterial 16S rRNA gene and fungal 18S rRNA gene with internal transcribed spacer (ITS) region was performed to characterize the change in microbial community composition in response to ACP treatment. The antimicrobial efficacy of ACP against a range of bacterial and fungal contaminants of wheat, was assessed to include individual isolates from grains as challenge pathogens. ACP influenced wheat microbiome composition, with a higher microbial diversity as well as abundance found on the untreated control grain samples. Culture and genomic approaches revealed different trends for mycoflora detection and control. A challenge study demonstrated that using direct mode of plasma exposure with 20 min of treatment significantly reduced the concentration of all pathogens. Overall, reduction levels for B. atrophaeus vegetative cells were higher than for all fungal species tested, whereas B. atrophaeus spores were the most resistant to ACP among all microorganisms tested. Of note, repeating sub-lethal plasma treatment did not induce resistance to ACP in either B. atrophaeus or A. flavus spores. ACP process control could be tailored to address diverse microbiological risks for grain stability and safety.

Inactivation Mechanism of Aspergillus flavus Conidia by High Hydrostatic Pressure.

This study investigated the inactivation mechanism of Aspergillus flavus conidia by high hydrostatic pressure (HHP). Activity counts, scanning electron microscopic (SEM) analysis, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) were used to study the effects of the HHP treatment on the morphology and protein composition of A. flavus spores. The results showed that that a 3-min-lasting 600 MPa treatment could completely abolish 107 colony-forming units/mL of live fungi. Furthermore, we also observed that lower spore viability corresponded to a higher Propidium Iodide absorption rate. The SEM images revealed that HHP disrupted the spore morphology and resulted in pore formation that led to the release of intracellular molecules, such as nucleic acids and proteins. The nucleic acid and protein concentration in the spore suspension increased in parallel with the increasing treatment pressure. The SDS-PAGE analysis showed that there were differences in the protein bands between the HHP-treated and untreated A. flavus spores, as the HHP treatment caused partial protein degradation and extracellular release. Therefore, the results of this study proved that high pressure could induce a morphological disruption in the internal and external cellular structures and degrade intracellular and extracellular proteins leading to an inactive state in A. flavus.

Sub3 inhibits Aspergillus flavus growth by disrupting mitochondrial energy metabolism, and has potential biocontrol during peanut storage.

Aspergillus flavus, a saprophytic fungus, is regularly detected in oil-enriched seeds. During colonization, this organism releases aflatoxins that pose a serious risk to food safety and human health. Therefore, an eco-friendly biological approach to inhibit the pathogen is desirable. Experimental results indicated that A. flavus spores could not germinate in potato dextrose broth culture medium, when the concentration of Sub3 exceeded 0.15 g L-1 . Morphological evaluation performed by flow cytometry and scanning electron microscopy indicated that spores were shrunken and pitted following Sub3 exposure. Physiological assessment using propidium iodide, 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolocarbocyanine iodide, 2,7-dichlorodihydrofluorescein diacetate and 4',6-diamidino-2-phenylindole staining revealed damaged cell membranes, decreased mitochondrial membrane potential, increased intracellular reactive oxygen species levels, and elevated large nuclear condensation and DNA fragmentation. Moreover, mitochondrial dehydrogenase activity was reduced by 29.42% and 45.48% after treatment with 0.1 and 0.15 g L-1 Sub3, respectively. Additionally, colonization capacity in peanut was significantly decreased, and the number of spores on seeds treated with Sub3 was decreased by 26.86% (0.1 g L-1 ) and 77.74% (0.15 g L-1 ) compared with the control group. Sub3 likely inhibits A. flavus by crossing the cell wall and targeting the cell membrane, disrupting mitochondrial energy metabolism, and inducing DNA damage, leading to spore death. Thus, Sub3 may provide a useful biocontrol strategy to control A. flavus growth in peanuts. © 2020 Society of Chemical Industry.

Pulsed light plasma treatment for the inactivation of Aspergillus flavus spores, Bacillus pumilus spores, and Escherichia coli O157:H7 in red pepper flakes

Pulsed light plasma (PLP) treatment was developed as a simultaneous treatment with cold plasma (CP) and intense pulsed light (IPL) to inactivate Aspergillus flavus spores, Bacillus pumilus spores, and Escherichia coli O157:H7 in red pepper flakes. PLP treatment non-thermally inactivated A. flavus spores, B. pumilus spores, and E. coli O157:H7 by 1.3 ± 0.1 log spores/g, 2.3 ± 0.2 log spores/g, and >3.8 log CFU/g Est. (estimated based on the number of survivors with counts below 20 on agar plates), respectively. PLP treatment did not alter the color and moisture content of the red pepper flakes. PLP treatment caused cell membrane degradation in A. flavus spores, B. pumilus spores, and E. coli O157:H7, as well as DNA damage to B. pumilus spores and E. coli O157:H7. The microbial inactivation efficacy of consecutive treatments with CP and IPL did not differ from that of PLP. Moreover, the inactivation efficacy was higher in flakes at aw 0.73 than at 0.57. The results of this study suggest that PLP treatment is a feasible non-thermal technology for decontaminating red pepper flakes.