Search Results (87)

Background/Objectives: Within their host trees, mountain pine beetles (MPBs, Dendroctonus ponderosae) interact with many fungal species, each releasing a unique profile of volatile organic compounds (VOCs). The FVOCs released by the two primary symbionts of MPBs, Grosmannia clavigera and Ophiostoma montium, have been found to enhance MPB attraction in the field and laboratory studies. Opportunistic, saprophytic fungal species, such as Aspergillus sp. and Trichoderma atroviride, are also common in MPB galleries and can negatively impact MPB fitness. However, little is known about the FVOCs produced by these fungal species and how they may impact MPB feeding and attraction. Methods: To address this knowledge gap, we characterized the FVOC profile of T. atroviride, and performed bioassays to test the effects of its FVOCs on MPB attraction and feeding activity. Results: Our chemical analysis revealed several FVOCs from T. atroviride known to inhibit the growth of competing fungal species and impact subcortical-beetle attraction. Conclusions: From those FVOCs, we recommended four compounds—2-pentanone, 2-heptanone, 2-pentanol, and phenylethyl alcohol—for use in future field tests as anti-attraction lures for MPBs. In bioassays, we also observed strong MPB repellency from FVOCs released by T. atroviride, as well as the mild effects of FVOCs on MPB feeding activity. Our findings highlight the potential for these FVOCs to be utilized in the development of more effective MPB anti-attractant lures, which are crucial for the monitoring and management of low-density MPB populations. Full article

Postharvest fungal diseases are a major cause of fruit spoilage and economic losses, particularly in perishable commodities like strawberries. In this study, a plant-derived Weissella paramesenteroides strain R2 was isolated from the mango fruit surface and evaluated for its antifungal potential. Dual-culture assays revealed the strong inhibitory activity of strain R2 against key postharvest pathogens, including Botrytis cinerea, Colletotrichum gloeosporioides, and Fusarium oxysporum. Notably, cell-free fermentation broth exhibited no antifungal activity, whereas the volatile organic compounds (VOCs) produced by R2 significantly suppressed fungal growth in sealed plate assays. GC-MS analysis identified 84 VOCs, with pyrazines as the dominant group. Three major compounds, 2,5-dimethylpyrazine, 2,4-di-tert-butylphenol, and 2-furanmethanol, were validated for their antifungal activity. The application of R2 VOCs in strawberry preservation significantly reduced disease incidence and severity during storage. These findings highlight W. paramesenteroides R2 as a promising, food-safe biocontrol agent for postharvest disease management via VOC-mediated mechanisms. Full article

Chalkbrood is the manifestation of the fungal disease caused by Ascosphaera apis, which affects broods of developing honeybees, particularly in Apis mellifera colonies. Recently, Metschnikowia pulcherrima has been proposed as a biocontrol agent in winemaking and for the management of major postharvest and soil-borne plant pathogenic fungi. In this study, the antagonistic activity of three M. pulcherrima strains against fifteen A. apis strains, isolated from contaminated hives of A. mellifera, was evaluated, with a specific focus on the potential antifungal activity of volatile organic compounds (VOCs). The study revealed that M. pulcherrima was effective against A. apis and that the antifungal activity was related to various mechanisms including competition for nutrients, secretion of pulcherriminic acid, and biosynthesis of specific antifungal VOCs. We also found that each M. pulcherrima strain produced a unique combination of VOCs, and the antifungal activity was strain-dependent and varied depending on the specific yeast-mold combination. In addition, preliminary analyses showed that a temperature of 30 °C and a higher amount of glucose (40 g/L) in the growing medium promote the growth of A. apis. These results could be useful for designing new strategies for the biocontrol of chalkbrood disease in honeybee colonies. Full article

The volatile organic compounds (VOCs) in Trichoderma afroharzianum ACCC 33109 have the biological activities of both hydrolytic enzymes and antimicrobial peptides to mitigate attack by phytopathogens and spread over long distances in soil. However, the biosynthesis pathway of anti-fungal VOCs has not been elucidated yet. In this study, we identified 15 genes (TaTS1–15) coding for putative terpene synthase with low identities (<79.54%) to functionally characterized homologs through genome mining. Upon Fusarium induction, the relative expression levels of nine TaTS genes were up-regulated by up to 2793-fold (TaTS9). To verify the contribution of TaTS9 to the synthesis of anti-fungal VOCs, the TaTS9 knockout mutant strain was constructed and characterized by its antagonistic activities, transcript profiles, and VOC metabolomes. Heterologous expression of TaTS9 in Escherichia coli produced the target gene product, which converted the precursor farnesyl pyrophosphate (FPP) into β-cubenene (>90%) and γ-amorphene. Thus, TaTS9 was confirmed as the first β-cubenene synthase of Trichoderma, which catalyzes the biosynthesis of various sesquiterpenes with anti-fungal activities. This study provides insight into the key terpene synthase gene in the biosynthesis of anti-fungal sesquiterpenoids for potential applications in the agriculture and food industries. Full article

Yeasts produce numerous antimicrobial agents such as killer toxins, volatile organic compounds (VOCs), and other secondary metabolites, establishing themselves in developing natural and sustainable biocontrol strategies for agriculture and food preservation. This study addressed the biocontrol potential of yeasts, isolated from spontaneous fermentations of rosehips (Rosa canina L.) and rowanberries (Sorbus aucuparia L.), focusing on their killer phenotypes and VOCs production. Yeasts were isolated using spontaneous fermentations with Hanseniaspora uvarum and Metschnikowia pulcherrima identified as the dominant species, comprising approximately 70% of the yeast population. Among 163 isolated strains, 20% demonstrated killing activity, with Saccharomyces cerevisiae exhibiting the strongest killing efficiency, as well as Pichia anomala and M. pulcherrima showing broad-spectrum antagonistic activity. This study identified dsRNA-encoded killer phenotypes in S. cerevisiae, S. paradoxus, and Torulaspora delbrueckii, revealing multiple distinct killer toxin types. The biocontrol potential of wild berry-inhabiting yeasts was demonstrated in a real food system, grape juice, where the S. cerevisiae K2-type killer strain significantly reduced fungal contaminants. The selected H. uvarum, M. pulcherrima, S. cerevisiae, and S. paradoxus yeast strains representing both berries were applied for VOC analysis and identification by gas chromatography-linked mass spectrometry. It was revealed that the patterns of emitted volatiles are yeast species-specific. Statistically significant differences between the individual VOCs were observed among killing phenotype-possessing vs. non-killer S. paradoxus yeasts, thus revealing the involvement of killer systems in multi-level biocontrol enablement. The performed studies deepen our understanding of potential yeast biocontrol mechanisms, highlight the importance of produced antimicrobials and volatiles in ensuring antagonistic efficacy, and prove the relevance of isolated biocontrol yeasts for improving food safety. Full article

Many endophytic fungi are approved as plant growth stimulants, and several commercial biostimulants have already been introduced in agricultural practice. However, there are still many species of fungi whose plant growth-promoting properties have been understudied or not studied at all. We examined the growth-promoting effect in spring barley (Hordeum vulgare) and Italian ryegrass (Lolium multiflorum) induced by three endophytic fungi previously obtained from the roots of Festuca/Lolium grasses. Surface-sterilized seeds were inoculated with a spore suspension of Cadophora fastigiata (isolate BSG003), Paraphoma fimeti (BSG010), Plectosphaerella cucumerina (BSG006), and their spore mixture. Before harvesting, the inoculated plants were grown in a greenhouse, with the barley being in multi-cavity trays for 30 days and ryegrass being placed in an original cylindric element system for 63 days. All three newly tested fungi had a positive effect on the growth of the barley and ryegrass plants, with the most pronounced impact observed in their root size. The fungal inoculations increased the dry shoot biomass between 11% and 26% in Italian ryegrass, but no such impact was observed in barley. The highest root increment was observed in barley. Herein, P. cucumerina and C. fastigiata inoculations were superior to other treatments, showing an increase in root dry weight of 50% compared to 20%, respectively. All fungal inoculations significantly promoted root growth in Italian ryegrass, resulting in a 20–30% increase in dry weight compared to non-inoculated plants. Moreover, a strong stimulatory effect of the fungi-emitted VOCs on the root development was observed in plate-in-plate arrays. In the presence of C. fastigiata and P. cucumerina cultures, the number of roots and root hairs in barley seedlings doubled compared to control plants. Thus, in our study, we demonstrated the potential of the grass root-derived endophytes C. fastigiata, P. fimeti, and P. cucumerina as growth promoters for spring barley and Italian ryegrass. These studies can be extended to other major crops and grasses by evaluating different fungal isolates. Full article

Plant–endophytic fungi are widely distributed and highly diverse, with many of them capable of influencing plant growth and development, which is related to the production of volatile organic compounds (VOCs). While certain fungal VOCs have been found to stimulate plant growth, others exhibit inhibitory effects. Importantly, the impact of fungal VOCs extends beyond host plants to affect non-host plants as well. In this study, we isolated two plant–endophytic fungi, Clonostachys sp. CC1 and Clonostachys sp. CC2, from healthy rice roots. These strains were co-cultured with both rice and Arabidopsis thaliana. Our results demonstrated that both strains significantly enhanced the growth of both rice and A. thaliana. Specifically, they increased the length and biomass of rice and A. thaliana seedlings, as well as the chlorophyll content, while decreasing the H₂O₂ content in the leaves of both plants. The VOCs produced by these strains were analyzed using gas chromatography–mass spectrometry (GC-MS), which identified a total of 10 main ingredients. Among these compounds, 1-pentanol, ethylbenzene, and dimethyl phthalate inhibited the growth of rice while promoting the growth of A. thaliana, highlighting the variability in the effects of these compounds on different plant species and the complexity of plant–fungal interactions. Full article

To investigate the dynamic changes and potential correlations between microbial diversity and volatile organic compounds (VOCs) during Chinese medium-temperature Daqu (MTD) manufacturing at different key stages, in this study, high-throughput sequencing (HTS) and gas chromatography–ion mobility spectrometry (GC–IMS) were employed to analyze the microbial diversity and VOCs of MTD, respectively. The results showed that Weissella, Staphylococcus, Thermoactinomyces, Kroppenstedtia, and Lactobacillus were the dominant bacterial genera, while Aspergillus, Alternaria, Thermoascus, Thermomyces, Wickerhamomyces, and Saccharomyces were the dominant fungal genera. A total of 61 VOCs were detected by GC–IMS, among which, 13 differential VOCs (VIP > 1) were identified, that could be used as potential biomarkers to judge the fermentation stage of MTD. Kroppenstedtia and Saccharopolyspora were positively correlated with 3-methyl-2-butenal and 2,2,4,6,6-pentamethylheptane-D, respectively, and both of these were positively correlated with butanal-D. Acetobacter, Streptomyces, and lactic acid bacteria (LAB) including Leuconostoc, Pediococcus, Weissella, and Lactobacillus were negatively correlated with their associated VOCs, while fungi were generally positively correlated with VOCs. Wickerhamomyces, Saccharomyces, and Candida were positively correlated with butan-2-one-M. This study provides a theoretical basis for explaining the mechanisms of MTD flavor formation and screening functional microorganisms to improve the quality of MTD. Full article

In this study, seed-surface-associated bacteria from fresh fruits of Capsicum spp. were analyzed to explore potential isolates for biocontrol of phytopathogenic fungal strains. A total of 76 bacterial isolates were obtained from three different species of chili pepper (C. annuum L., C. pubescens R. & P., and C. chinense Jacq.), and two isolates were selected via mycelial growth inhibition assays based on their production of volatile organic compounds (VOCs) against six fungal strains. Genomic analysis identified these isolates as Bacillus altitudinis CH05, with a chromosome size of 3,687,823 bp and with 41.25% G+C, and Bacillus tropicus CH13, with a chromosome size of 5,283,706 bp and with 35.24% G+C. Both bacterial strains showed high mycelial growth inhibition capacities against Sclerotium rolfsii, Sclerotinia sp., Rhizoctonia solani, and Alternaria alternata but lower inhibition capacities against Colletotrichum gloesporoides and Fusarium oxysporum. VOC identification was carried out after 24 h of fermentation with 64 VOCs for B. altitudinis CH05 and 53 VOCs for B. tropicus CH13. 2,5-Dimethyl pyrazine and acetoin had the highest relative abundance values in both bacterial strains. Our findings revealed that seed-surface-associated bacteria on Capsicum spp. have the metabolic ability to produce VOCs for biocontrol of fungal strains and have the potential to be used in sustainable agriculture. Full article

Fungal phytopathogens represent a large and economically significant challenge to food production worldwide. Thus, the application of biocontrol agents can be an alternative. In the present study, we carried out biological, metabolomic, and genetic analyses of three endophytic isolates from nodules of Chamaecytisus albus, classified as Pseudomonas chlororaphis acting as antifungal agents. The efficiency of production of their diffusible and volatile antifungal compounds (VOCs) was verified in antagonistic assays with the use of soil-borne phytopathogens: B. cinerea, F. oxysporum, and S. sclerotiorum. Diffusible metabolites were identified using chromatographic and spectrometric analyses (HPTLC, GC-MS, and LC-MS/MS). The phzF, phzO, and prnC genes in the genomes of bacterial strains were confirmed by PCR. In turn, the plant growth promotion (PGP) properties (production of HCN, auxins, siderophores, and hydrolytic enzymes, phosphate solubilization) of pseudomonads were bioassayed. The data analysis showed that all tested strains have broad-range antifungal activity with varying degrees of antagonism. The most abundant bioactive compounds were phenazine derivatives: phenazine-1-carboxylic acid (PCA), 2-hydroxy-phenazine, and diketopiperazine derivatives as well as ortho-dialkyl-aromatic acids, pyrrolnitrin, siderophores, and HCN. The results indicate that the tested P. chlororaphis isolates exhibit characteristics of biocontrol organisms; therefore, they have potential to be used in sustainable agriculture and as commercial postharvest fungicides to be used in fruits and vegetables. Full article

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. Full article

The causal agent of tomato leaf mold, Cladosporium fulvum, is prevalent in greenhouses worldwide, especially under high humidity conditions. Despite its economic impact, studies on antifungal agents targeting C. fulvum remain limited. This study evaluates biocontrol agents (BCAs) as alternatives to chemical controls for managing this disease, alongside the strobilurin fungicide azoxystrobin. From a Moroccan collection of potential BCAs, five bacterial isolates (Alcaligenes faecalis ACBC1, Pantoea agglomerans ACBC2, ACBP1, ACBP2, and Bacillus amyloliquefaciens SF14) and three fungal isolates (Trichoderma spp. OT1, AT2, and BT3) were selected and tested. The in vitro results demonstrated that P. agglomerans isolates reduced mycelial growth by over 60% at 12 days post-inoculation (dpi), while Trichoderma isolates achieved 100% inhibition in just 5 dpi. All bacterial isolates produced volatile organic compounds (VOCs) with mycelial inhibition rates ranging from 38.8% to 57.4%. Likewise, bacterial cell-free filtrates significantly inhibited the pathogen’s mycelial growth. Greenhouse tests validated these findings, showing that all the tested isolates were effective in reducing disease incidence and severity. Azoxystrobin effectively impeded C. fulvum growth, particularly in protective treatments. Fourier transform infrared spectroscopy (FTIR) analysis revealed significant biochemical changes in the treated plants, indicating fungal activity. This study provides valuable insights into the efficacy of these BCAs and azoxystrobin, contributing to integrated management strategies for tomato leaf mold disease. Full article

Finishing coatings in the wood-based composites industry not only influence the final appearance of the product but also serve to protect against fungi and molds and reduce the release of harmful substances, particularly formaldehyde and volatile organic compounds (VOCs). Carbon-rich materials, such as those derived from birch bark extraction, specifically suberin acids, can fulfill this role. Previous research has demonstrated that adding suberin acid residues (SAR) at 20% and 50% by weight significantly enhances the gas barrier properties of surface-finishing materials based on poly(lactide) (PLA) and polycaprolactone (PCL), particularly in terms of total VOC (TVOC) and formaldehyde emissions. This study aims to explore whether these properties can be further improved through the incorporation of nano-zinc oxide (nano-ZnO). Previous research has shown that these nanoparticles possess strong resistance to biological factors and can positively affect the characteristics of nanofilms applied as surface protection. The study employed PLA and PCL finishing layers blended with SAR powder at 10% w/w and included 2% and 4% nano-zinc oxide nanoparticles. The resulting blends were milled to create a powder, which was subsequently pressed into 1 mm-thick films. These films were then applied to raw particleboard surfaces. TVOC and formaldehyde emission tests were conducted. Additionally, the fungal resistance of the coated surfaces was assessed. The results showed that PLA/SAR and PCL/SAR composites with the addition of nano-zinc oxide nanoparticles exhibited significantly improved barrier properties, offering a promising avenue for developing biodegradable, formaldehyde-free coatings with enhanced features in the furniture industry. Furthermore, by utilizing SAR as a post-extraction residue, this project aligns perfectly with the concept of upcycling. Full article

Selenium-enriched Lentinus edodes (SL) is a kind of edible fungi rich in organic selenium and nutrients. Monascus purpureus with high monacolin K (MK) production and Saccharomyces cerevisiae were selected as the fermentation strains. A single-factor experiment and response surface methodology were conducted to optimize the production conditions for MK with higher contents from selenium-enriched Lentinus edodes fermentation (SLF). Furthermore, we investigated the nutritional components, antioxidant capacities, and volatile organic compounds (VOCs) of SLF. The MK content in the fermentation was 2.42 mg/g under optimal fermentation conditions. The organic selenium content of SLF was 7.22 mg/kg, accounting for 98% of the total selenium content. Moreover, the contents of total sugars, proteins, amino acids, reducing sugars, crude fiber, fat, and ash in SLF were increased by 9%, 23%, 23%, 94%, 38%, 44%, and 25%, respectively. The antioxidant test results demonstrated that 1.0 mg/mL of SLF exhibited scavenging capacities of 40%, 70%, and 79% for DPPH, ABTS, and hydroxyl radicals, respectively. Using gas chromatography–ion mobility spectrometry technology, 34 unique VOCs were identified in SLF, with esters, alcohols, and ketones being the main components of its aroma. This study showed that fungal fermentation provides a theoretical reference for enhancing the nutritional value of SL. Full article

Terpenoids are structurally diverse natural products that have been widely used in the pharmaceutical, food, and cosmetic industries. Research has shown that fungi produce a variety of terpenoids, yet fungal terpene synthases remain not thoroughly explored. In this study, the tps1 gene, a crucial component of the terpene synthetic pathway, was isolated from Trichoderma atroviride HB20111 through genome mining. The function of this gene in the terpene synthetic pathway was investigated by constructing tps1-gene-deletion- and overexpression-engineered strains and evaluating the expression differences in the tps1 gene at the transcript level. HS-SPME-GC-MS analysis revealed significant variations in terpene metabolites among wild-type, tps1-deleted (Δtps1), and tps1-overexpressed (Otps1) strains; for instance, most sesquiterpene volatile organic compounds (VOCs) were notably reduced or absent in the Δtps1 strain, while nerolidol, β-acorenol, and guaiene were particularly produced by the Otps1 strain. However, both the Δtps1 and Otps1 strains produced new terpene metabolites compared to the wild-type, which indicated that the tps1 gene played an important role in terpene synthesis but was not the only gene involved in T. atroviride HB20111. The TPS1 protein encoded by the tps1 gene could function as a sesquiterpene cyclase through biological information and evolutionary tree analysis. Additionally, fungal inhibition assay and wheat growth promotion assay results suggested that the deletion or overexpression of the tps1 gene had a minimal impact on fungal inhibitory activity, plant growth promotion, and development, as well as stress response. This implies that these activities of T. atroviride HB20111 might result from a combination of multiple metabolites rather than being solely dependent on one specific metabolite. This study offers theoretical guidance for future investigations into the mechanism of terpenoid synthesis and serves as a foundation for related studies on terpenoid metabolic pathways in fungi. Full article