RESUMEN
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.
Asunto(s)
Hongos , Fungicidas Industriales , Humanos , Antifúngicos/farmacología , Fungicidas Industriales/farmacología , Grano Comestible/microbiologíaRESUMEN
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.
Asunto(s)
Antifúngicos , Aspergillus flavus , Antifúngicos/farmacología , Antifúngicos/metabolismo , Aldehídos/metabolismo , MetabolómicaRESUMEN
Biogenic volatile organic compounds hold remarkable potential for controlling fungal decay in agro- and food products. Recently, we reported that linalool, the major volatile component of the Zanthoxylum schinifolium pericarp, showed great potential as a biofumigant to control Aspergillus flavus growth in postharvest grains. In this study, the inhibitory effects of linalool on A. flavus growth in stored grains and its underlying mechanism were investigated through transcriptomic and biochemical analyses. Linalool vapor at 800 µL/L can effectively prevent A. flavus growth in 22% moisture wheat grains. Linalool at 2 µL/mL completely inhibited the germination of A. flavus spores, and 10 µL/mL caused spore death. Scanning electron microscopy revealed that linalool treatment caused wrinkling and spore breakage. Transcriptomics showed that 3806 genes were significantly differentially expressed in A. flavus spores exposed to 2 µL/mL linalool, predominantly showing enrichment regarding the ribosome, DNA replication, glutathione metabolism, peroxisome, and MAPK signaling pathways. Flow cytometry showed that linalool treatment caused hyperpolarization of mitochondrial membrane potential. 4,6-Diamidino-2-phenylindole staining indicated that linalool caused DNA fragmentation in A. flavus spores, and monodansylcadaverine staining confirmed that linalool induced autophagy in A. flavus spores. We thus propose that linalool can damage the plasma membrane, cause mitochondrial dysfunction and DNA damage, and induce autophagy in A. flavus spores. These findings considerably improve our understanding of the mechanisms underlying the inhibitory effects of linalool on A. flavus, which is crucial regarding the development of applications to prevent postharvest grain spoilage due to A. flavus infestations. KEY POINTS: ⢠The inhibitory potency of linalool on A. flavus spore germination was determined. ⢠Transcriptomic analyses were performed to identify differentially expressed genes of A. flavus exposed to linalool. ⢠A functional mechanism underlying the inhibitory effects of linalool on A. flavus spore germination is proposed.
Asunto(s)
Aspergillus flavus , Compuestos Orgánicos Volátiles , Monoterpenos Acíclicos , Antifúngicos/farmacología , Glutatión/metabolismo , Esporas Fúngicas , Compuestos Orgánicos Volátiles/metabolismoRESUMEN
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.
Asunto(s)
Aspergillus flavus , Fungicidas Industriales , 1-Octanol/metabolismo , 1-Octanol/farmacología , Antifúngicos/química , Fungicidas Industriales/farmacología , Esporas FúngicasRESUMEN
The exploitation of plant volatile organic compounds as biofumigants to control postharvest decaying of agro-products has received considerable research attention. Our previous study reported that 1-nonanol, the main constituent of cereal volatiles, can inhibit Aspergillus flavus growth and has the potential as a biofumigant to control the fungal spoilage of cereal grains. However, the antifungal mechanism of 1-nonanol against A. flavus is still unclear at the molecular level. In this study, the minimum inhibitory concentration and minimum fungicidal concentration of 1-nonanol against A. flavus spores were 2 and 4 µL/mL, respectively. Scanning electron microscopy revealed that the 1-nonanol can distort the morphology of A. flavus spore. Annexin V-FITC/PI double staining showed that 1-nonanol induced phosphatidylserine eversion and increased membrane permeability of A. flavus spores. Transcriptional profile analysis showed that 1-nonanol treatment mainly affected the expression of genes related to membrane damage, oxidative phosphorylation, blockage of DNA replication, and autophagy in A. flavus spores. Flow cytometry analysis showed that 1-nonanol treatment caused hyperpolarization of mitochondrial membrane potential and accumulation of reactive oxygen species in A. flavus spores. 4',6-diamidino-2-phenylindole staining showed that treatment with 1-nonanol destroyed the DNA. Biochemical analysis results confirmed that 1-nonanol exerted destructive effects on A. flavus spores by decreasing intracellular adenosine triphosphate content, reducing mitochondrial ATPase activity, accumulating hydrogen peroxide and superoxide anions, and increasing catalase and superoxide dismutase enzyme activities. This study provides new insights into the antifungal mechanisms of 1-nonanol against A. flavus. KEY POINTS: ⢠1-Nonanol treatment resulted in abnormal morphology of A. flavus spores. ⢠1-Nonanol affects the expression of key growth-related genes of A. flavus. ⢠The apoptosis of A. favus spores were induced after exposed to 1-nonanol.
Asunto(s)
Aspergillus flavus , Transcriptoma , Antifúngicos/metabolismo , Antifúngicos/farmacología , Aspergillus flavus/metabolismo , Alcoholes Grasos/metabolismo , Esporas FúngicasRESUMEN
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.
Asunto(s)
Aldehídos , Aspergillus flavus , Antifúngicos , Aspergillus flavus/genética , Perfilación de la Expresión Génica , Esporas FúngicasRESUMEN
Chemical control of fungal spoilage of postharvest cereal grains is an important strategy for the management of grain storage. Here, the potential antifungal activity of 1-nonanol, a main component of cereal volatiles, against Aspergillus flavus was studied. The growth of A. flavus was completely inhibited by 0.11 and 0.20 µL/mL 1-nonanol at vapor and liquid contact phases, respectively. Metabolomic analysis identified 135 metabolites whose expression was significantly different between 1-nonanol-treated and untreated A. flavus. These metabolites were involved in the tricarboxylic acid cycle, amino acid biosynthesis, protein degradation and absorption, aminoacyl-tRNA biosynthesis, mineral absorption, and in interactions with ABC transporters. Biochemical validation confirmed the disruptive effect of 1-nonanol on A. flavus growth, as indicated by the leakage of intracellular electrolytes, decreased succinate dehydrogenase, mitochondrial dehydrogenase, and ATPase activity, and the accumulation of reactive oxygen species. We speculated that 1-nonanol could disrupt cell membrane integrity and mitochondrial function and might induce apoptosis of A. flavus mycelia. Simulated grain storage experiments showed that 1-nonanol vapor, at a concentration of 264 µL/L, completely inhibited A. flavus growth in wheat, corn, and paddy grain with an 18% moisture content. This study provides new insights into the antifungal mechanism of 1-nonanol against A. flavus, indicating that it has a promising potential as a bio-preservative to prevent fungal spoilage of postharvest grains. KEY POINTS: ⢠1-Nonanol showed higher antifungal activity against A. flavus. ⢠The antifungal mechanisms of 1-nonanol against A. flavus were revealed. ⢠1-Nonanol could damage cell membrane integrity and mitochondrial function.
Asunto(s)
Antifúngicos , Aspergillus flavus , Antifúngicos/farmacología , Alcoholes Grasos , MetabolómicaRESUMEN
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.
Asunto(s)
Aflatoxinas , Aspergillus flavus , Aflatoxinas/metabolismo , Aldehídos , Antifúngicos/metabolismo , Antifúngicos/farmacología , Apoptosis , Mitocondrias , Esporas Fúngicas/metabolismoRESUMEN
Hexanal, a natural volatile organic compound, exerts antifungal activity against Aspergillus flavus; however, the mechanisms underlying these effects are unclear. In this study, we found that the growth of A. flavus mycelium was completely inhibited following exposure to 0.4 µL/mL hexanal (minimal inhibitory concentration). A detailed metabolomics survey was performed to identify changes in metabolite production by A. flavus cells after exposure to 1/2 the minimal inhibitory concentration of hexanal for 6 h, which revealed significant differences in 70 metabolites, including 20 upregulated and 50 downregulated metabolites. Among them, levels of L-malic acid, α-linolenic acid, phosphatidylcholine, D-ribose, riboflavin, D-mannitol, D-sorbitol, and deoxyinosine were significantly reduced. The metabolomics results suggest that the metabolites are mainly involved in the tricarboxylic acid cycle (TCA), ABC transport system, and membrane synthesis in A. flavus cells. Hexanal treatment reduced succinate dehydrogenase and mitochondrial dehydrogenase activity and stimulated superoxide anion and hydrogen peroxide accumulation in A. flavus mycelia. Increases in the electric conductivity and A260nm of the culture supernatant indicated cell membrane leakage. Therefore, hexanal appears to disrupt cell membrane synthesis, induce mitochondrial dysfunction, and increase oxidative stress in A. flavus mycelia. KEY POINTS: ⢠Metabolite changes of A. flavus mycelia were identified after hexanal treatment. ⢠Most differential metabolites were downregulated in hexanal-treated A. flavus. ⢠An antifungal model of hexanal against A. flavus was proposed.
Asunto(s)
Aldehídos , Aspergillus flavus , Antifúngicos/farmacología , MetabolómicaRESUMEN
ß-1,3-glucanases, the plant PR-2 family of pathogenesis-related (PR) proteins, can be constitutively expressed and induced in wheat crop to enhance its anti-fungal pathogen defense. This study aimed to investigate the inhibitory effect of wheat ß-1,3-glucanase on fungi most commonly associated with wheat kernel. A ß-1,3-glucanase from wheat was successfully expressed in Pichia pastoris X-33 and its biochemical and antifungal properties were characterized herein. The molecular weight of recombinant ß-1,3-glucanase is approximately 33 kDa. ß-1,3-glucanase displays optimal activity at pH 6.5, remaining relatively high at pH 5.5-8.0. The optimal reaction temperature of ß-1,3-glucanase is 50⯰C, retaining approximately 84.0% residual activity after heat-treated at 50⯰C for 1â¯h. The steady-state kinetic parameters of ß-1,3-glucanase against laminarin was determined and the Km and Vmax were 1.32⯱â¯0.20â¯mg/ml and 96.4⯱â¯4.4 Uâ¯mg-1 protein, respectively. The inhibitory effect of purified ß-1,3-glucanase against the seven fungi commonly associated with wheat kernel was assessed in vitro. ß-1,3-glucanase exerted differential inhibitory effects on hyphal growth of Fusarium graminearum, Alternaria sp., A. glaucus, A. flavus, A. niger, and Penicillium sp. Spore formation and mycelial morphology of Alternaria sp., A. flavus, and A. niger were significantly affected by ß-1,3-glucanase (1U). The present results would help elucidate the mechanism underlying the inhibition of wheat ß-1,3-glucanases on pathogens.
Asunto(s)
Antifúngicos , Endo-1,3(4)-beta-Glucanasa , Hongos Mitospóricos/crecimiento & desarrollo , Proteínas de Plantas , Triticum , Antifúngicos/química , Antifúngicos/aislamiento & purificación , Antifúngicos/farmacología , Endo-1,3(4)-beta-Glucanasa/química , Endo-1,3(4)-beta-Glucanasa/genética , Endo-1,3(4)-beta-Glucanasa/aislamiento & purificación , Endo-1,3(4)-beta-Glucanasa/farmacología , Calor , Concentración de Iones de Hidrógeno , Pichia/enzimología , Pichia/genética , Proteínas de Plantas/química , Proteínas de Plantas/genética , Proteínas de Plantas/aislamiento & purificación , Proteínas de Plantas/farmacología , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/aislamiento & purificación , Proteínas Recombinantes/farmacología , Triticum/enzimología , Triticum/genéticaRESUMEN
Feruloyl esterases (FAEs) are key enzymes involved in the complete biodegradation of lignocelluloses, which could hydrolyze the ester bonds between hemicellulose and lignin. The coding sequence of a feruloyl esterase A (AtFaeA) was cloned from Aspergillus terreus and the recombinant AtFaeA was constitutively expressed in Pichia pastoris. The SDS-PAGE analysis of purified AtFaeA showed two protein bands owing to the different extent of glycosylation, and the recombinant AtFaeA had an optimum temperature of 50°C and an optimum pH of 5.0. The substrate utilization and primary sequence identity of AtFaeA demonstrated that it is a type-A feruloyl esterase. The hydrolysis of corn stalk and corncob by xylanase from Aspergillus niger could be significantly improved in concert with recombinant AfFaeA.
Asunto(s)
Aspergillus/enzimología , Hidrolasas de Éster Carboxílico/genética , Hidrolasas de Éster Carboxílico/metabolismo , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Secuencia de Aminoácidos , Aspergillus/genética , Biodegradación Ambiental , Biomasa , Hidrolasas de Éster Carboxílico/química , Hidrolasas de Éster Carboxílico/aislamiento & purificación , Escherichia coli , Datos de Secuencia Molecular , Pichia , Proteínas Recombinantes/química , Proteínas Recombinantes/aislamiento & purificación , Alineación de Secuencia , Zea maysRESUMEN
The growth of toxigenic fungi can adversely affect grain quality and even produce mycotoxins of food safety concern, which should be sensitively monitored and controlled during grain storage. To establish the relationship between the growth of toxigenic fungi and their carbon dioxide (CO2) production, the pattern of CO2 concentration changes was studied during the fungal growth in grain. The results showed the CO2 concentrations increased exponentially (r ≥ 0.96) during the growth of toxigenic fungi Aspergillus flavus, Penicillium sp. and Aspergillus ochraceus, which was different from the linear increase of CO2 concentration produced by the non-toxigenic xerophilic fungi Aspergillus glaucus and Aspergillus restrictus. The acceleration of CO2 concentration was found much earlier than the growth of toxigenic fungi, which would be useful for the prevention of grain spoilage. In addition, the CO2 concentration changes were also determined in storage containers loaded with grain of different moisture content and significant correlation (p < 0.05) was found between changes of CO2 concentration and fungal growth as well as mycotoxin production. The nonlinear increase of CO2 concentration in stored grains could be considered as an indication of the rapid growth of toxigenic fungi and greater risk of microbial spoilage of grains. The results can provide a valid foundation for the prevention of toxigenic fungi and mycotoxin production in stored grains through monitoring the CO2 concentration changes.
Asunto(s)
Aspergillus/crecimiento & desarrollo , Dióxido de Carbono/análisis , Grano Comestible/microbiología , Contaminación de Alimentos/prevención & control , Microbiología de Alimentos , Almacenamiento de Alimentos , Micotoxinas/análisis , Oryza/microbiología , Penicillium/crecimiento & desarrollo , Triticum/microbiología , Zea mays/microbiologíaRESUMEN
A novel actinobacterial strain, 3-wff-81(T), was isolated from interfacial sediment of the eutrophic Taihu Lake in Jiangsu Province (China) and subjected to polyphasic taxonomic characterization. The strain formed pale orange-pigmented colonies comprising rod-shaped cells on R2A agar. Phylogenetic analysis based on the 16S rRNA gene sequences showed that strain 3-wff-81(T) belonged to the genus Geodermatophilus, with Geodermatophilus soli PB34(T) (99.1â% similarity) and Geodermatophilus terrae PB261(T) (98.3â% similarity) as closest relatives. The major fatty acids were 16â:â0 iso, 15â:â0 iso, 17â:â1ω8c and 14â:â0 iso. The predominant menaquinones were MK-9(H4) and MK-9. Polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol and phosphatidylinositol mannosides. The genomic DNA G+C content was 73.2 mol%. DNA-DNA relatedness values with G. soli PB34(T) and G. terrae PB261(T) were 42.8â% and 39.6â%, respectively. Based on the physiological, biochemical and chemotaxonomic data, it is proposed that strain 3-wff-81(T) represents a novel species named Geodermatophilus taihuensis sp. nov. with 3-wff-81(T) (â=âCGMCC 1.12303(T)â=âNBRC 109416(T)) as the type strain.
Asunto(s)
Actinomycetales/clasificación , Sedimentos Geológicos/microbiología , Filogenia , Actinomycetales/genética , Actinomycetales/aislamiento & purificación , Técnicas de Tipificación Bacteriana , Composición de Base , China , ADN Bacteriano/genética , Ácidos Grasos/química , Lagos/microbiología , Datos de Secuencia Molecular , Hibridación de Ácido Nucleico , ARN Ribosómico 16S/genética , Análisis de Secuencia de ADN , Vitamina K 2/análogos & derivados , Vitamina K 2/química , Microbiología del AguaRESUMEN
A polyphasic study was carried out to clarify the taxonomic position of a novel strain R-30(T) isolated from the surficial layer of sediment from Taihu Lake of China. The strain formed pink colored colonies comprising coccodial cells on R2A agar. Phylogenetic analysis based on the 16S rRNA gene sequences showed that strain R-30(T) clustered with the strains of genus Roseococcus and strain Rubritepida flocculans, with Roseococcus suduntuyensis SHET(T) as the closest relative, sharing 95.6% similarity. The major fatty acids (ï¼5%) were 18ï¼1ω7c (66.7%), 16ï¼ 1ω7c/16ï¼1ω6c (10.2%) and 16ï¼0 (8.0%). The major polar lipids were diphosphatidyl glycerol (DPG), phosphatidyl methylethanolamine (PME), phosphatidyl ethanolamine (PE) and phosphatidyl choline (PC). The genomic DNA G+C content was 73.9 mol%. On the basis of the phylogenetic analysis and physiological and biochemical characteristics, we conclude that strain R-30(T) represents a novel genus and species of the family Acetobacteraceae, for which we propose the name Sediminicoccus rosea gen nov. sp. nov. with R-30(T) (= CGMCC 1.12302(T) = NBRC 109675(T)) as the type species and type strain.