Search Results (191)

The complex polysaccharide pullulan is characterized as a glucose-containing biopolymer that is both water-soluble and neutral in polarity. A variety of commercial applications exist for pullulan, including its utilization as a flocculant, a blood plasma substitute, a food additive, a dielectric material, an adhesive, or a packaging film. The fungus Aureobasidium pullulans has used several hydrolysates derived from plant biomass or starch-containing processing coproducts to support polysaccharide production. These include various plant biomass or processing coproduct streams such as lignocellulosic-containing peat, prairie grass, stalks, hulls, straw, shells, and pods or starch-containing coproducts from the processing of corn, rice, jackfruit seeds, palm kernels, cassava, and potatoes. The pullulan concentration produced by A. pullulans and the pullulan content of the polysaccharide depend on the plant hydrolysate carbon content and the strain used. If a lower-cost culture medium for fungal pullulan production were to be developed, a more economical approach to synthesizing commercial pullulan would be the utilization of plant-derived hydrolysates. This review examines the ability of selected hydrolysates of lignocellulosic plant biomass or plant-derived starch-containing processing coproducts to support A. pullulans polysaccharide synthesis in order to identify those substrates with the greatest potential for reducing the cost of commercial pullulan. Full article

Microbial polysaccharides are promising components for wound-care products. This study reports the development of wound-healing antimicrobial hydrogels, based on pullulan from Aureobasidium pullulans, combined with mesenchymal cell-derived conditioned medium. Structural characterization of pullulan was confirmed by FTIR and NMR. Twenty-three formulations containing pullulan, chitosan, gelatin, citric acid, and antimicrobial agents were prepared. Physicochemical screening identified optimal hydrogels: No. 22 (1.2% pullulan, 1.2% chitosan, 0.2% citric acid, 2.4% gelatin, 0.1% conditioned medium, 0.4% glutaraldehyde) and No. 23 (2.4% pullulan, no chitosan, the remaining components identical to those in No. 22). Both exhibited pH values of 5.34 and 5.49, moisture content of 92%, swelling capacities of 175% and 213%, and dynamic viscosity between 58–120 mPa·s. Cytotoxicity testing with human mesenchymal stem cells showed no significant toxicity, with both hydrogels supporting cell adhesion and proliferation. Antimicrobial assays demonstrated inhibitory activity against Staphylococcus aureus and Escherichia coli for both formulations; only hydrogel No. 23 inhibited Pseudomonas aeruginosa. In vitro scratch assays revealed that hydrogel No. 23 significantly promoted fibroblast migration, achieving 30.25% scratch closure after 24 h. The developed formulations combine favorable physicochemical properties with antimicrobial efficacy and regenerative potential, supporting further evaluation as advanced wound-healing and anti-burn dressings. Full article

Extremotolerant fungi inhabit environments with multiple overlapping stressors, yet most studies examine stresses individually. We tested whether preconditioning with salt, cold, or both improves survival after desiccation and freezing, and whether combined salinity and temperature effects on growth are additive or synergistic. We studied Aureobasidium pullulans, Aureobasidium subglaciale, Aureobasidium melanogenum, and Hortaea werneckii (haploid and diploid). All preconditioning treatments significantly increased long-term desiccation survival in A. pullulans, reflecting its generalist capacity to activate cross-protective responses. H. werneckii displayed smaller improvements, consistent with a specialist strategy. Freezing survival without cryoprotectants remained ~100% in both species, indicating high intrinsic tolerance. Growth analyses revealed synergistic effects of salinity and temperature in Aureobasidium spp. Species differed in salinity sensitivity (A. melanogenum > A. pullulans > A. subglaciale) and thermal preferences. A. melanogenum and A. pullulans grew faster at higher temperatures, while A. subglaciale showed the opposite trend. In H. werneckii, salinity governed growth. Haploids slowed as salinity increased, while the diploid remained unaffected. This is the first confirmation of the long-standing suggestion that hybrid diploid genomes of many H. werneckii are an adaptation to osmotic stress. These findings illustrate two pathways to extremotolerance: inducible flexibility in Aureobasidium versus constitutive halotolerance in H. werneckii. Full article

This study investigated the effects of solid-state fermentation with a compound microbial inoculant on the nutritional composition, microbial community structure, and metabolic products of green jujube (Ziziphus mauritiana Lam.) straw. The results demonstrated that solid-state fermentation significantly enhanced the nutritional value of the straw, as evidenced by a marked increase in crude protein content and significant reductions in neutral detergent fiber (NDF), acid detergent fiber (ADF), and cellulose content. Metagenomic analysis revealed that fermentation substantially altered the microbial community structure of the straw, with a pronounced increase in the relative abundance of bacteria from the phylum Pseudomonadota (particularly genera such as Klebsiella and Enterobacter), and an upward trend in the abundance of fungi from the phylum Basidiomycota (Astraeus). Functional annotation indicated that fermentation enhanced the potential of the straw microbiota in genetic information processing, ABC transporters, and starch and sucrose metabolism, while attenuating the oxidative phosphorylation pathway. Metabolomic analysis identified 1176 differential metabolites, with significant increases in bioactive compounds such as peptides, amino acids, polyunsaturated fatty acids, and flavonoids following fermentation. Correlation analysis further revealed significant associations between specific microorganisms (Klebsiella, Enterobacter, and Aureobasidium) and key metabolites (amino acids, peptides, and flavonoids) in the fermented green jujube straw. This study confirms that solid-state fermentation can effectively improve the nutritional value and functional properties of the agricultural by-product green jujube straw by reshaping its microbial ecosystem and metabolic network. Full article

Extreme environments are a largely unexplored reservoir of microbial diversity, with a remarkable potential to be exploited in agriculture. One hundred and seventeen yeast isolates, derived from different ecosystems in Italy, Sweden, Algeria, and France, were molecularly identified, and the most represented genus was Aureobasidium (57%). A phylogenetic analysis based on a multi-locus sequence typing (ITS, ELO, EF-1alpha) was conducted to characterize the black yeasts’ population. To investigate A. pullulans extremophilic and extremotolerant behaviour, different temperatures and pH, together with the enzymatic production, were evaluated. The strains were tested by in vitro and in vivo assays against the postharvest fungal pathogen Monilinia fructicola as potential biocontrol agents (BCAs). Results displayed a great ecological variability concerning strains’ growth and cell production depending on different culture conditions. However, a remarkable thermotolerance aptitude was detected in almost all the strains. In particular, the strains belonging to Group 2 (Algerian Desert) and 3 (Alto Adige Region) showed, respectively, higher thermotolerance and biocontrol ability. These findings showed how some extreme environments could represent a promising source for new potential BCAs. However, further studies are needed to investigate the mechanisms of action of these putative BCAs for application during the postharvest phase. Full article

Luteolin is a naturally occurring flavonoid with growing interest for its senolytic properties. However, its poor water solubility and low bioavailability limit clinical application. This study aimed to develop and compare two types of nanocarriers, liposomes and polymeric nanoparticles, for the efficient delivery of luteolin in senolytic therapies. Liposomes with luteolin were prepared using the lipid film hydration method, followed by sonication and extrusion. Polymeric nanoparticles were developed via the nanoprecipitation method using pullulan acetate, a hydrophobic derivative obtained by chemical functionalization of pullulan. Pullulan was biosynthesized over 72 h using the microorganism Aureobasidium pullulans ICCF 36 (from CMII–INCDCF-ICCF). The formulation used a polymer-to-luteolin ratio of 10:1 (g/g) and Pluronic F127 as a stabilizer. Nanoprecipitation was carried out under controlled conditions: stirring at 700 rpm and dropwise addition at 0.5 mL/min. Luteolin was successfully encapsulated in both delivery systems. Liposomes showed an encapsulation efficiency of 85.07 ± 0.09% and nanoscale diameter. Polymeric nanoparticles demonstrated an encapsulation efficiency of 74.87 ± 0.05%, nanometric size and a formulation yield of 73.29 ± 0.09%. Both liposomal and polymeric nanoparticle systems effectively encapsulated luteolin, with high efficiency and yield. The formulations present promising potential for use in senolytic therapies, targeting age-related cellular dysfunction. Further studies will assess their release kinetics, biological activity, and senolytic effects in vitro and in vivo. Full article

Ten phyllospheric yeast strains were studied for their potential as biocontrol agents against fruit spoilage mould. The efficacy of these yeasts against Botrytis cinerea and Fusarium fujikuroi was assessed using dual-culture, mouth-to-mouth, radial growth inhibition and post-harvest fruit assays. Additionally, their capacity for producing hydrolytic enzymes was examined. Results from the ten yeasts revealed dual culture antagonism ranging from 41% to 63% against B. cinerea and 23% to 48% against F. fujikuroi, along with radial inhibition ranging from 70% to 100% and 47% to 100%, respectively. Additionally, in vitro inhibition through the production of volatile organic compounds (VOCs) varied from 2% to 46% against B. cinerea and 6% to 64% against F. fujikuroi. Overall, Aureobasidium melanogenum J7, Suhomyces pyralidae Y1117, Dekkera anomala V38, and Rhodotorula diarenensis J43 emerged as the best-performing biocontrol yeasts. Volatile organic compounds produced by the four yeasts were also identified and included in fruit bioassays using pears and tomatoes. Various VOCs, including 1-butanol, 3-methylbutanol, and butyric acid, were linked to the antagonistic properties of the selected yeasts. Lastly, the four chosen yeast strains significantly mitigated post-harvest spoilage caused by B. cinerea and F. fujikuroi in pear and tomato fruits, with D. anomala V38 exhibiting the greatest inhibitory activity. These findings underscore a potential sustainable and efficient approach to reducing mould-induced post-harvest spoilage while reducing reliance on synthetic fungicides. Full article

This study characterised the diversity of filamentous fungi and yeasts during Malbec grape fermentation in the Southern Oasis of Mendoza (Argentina) winegrowing region, under different sanitary conditions and SO₂ treatments, using morphological and ITS-RFLP-based molecular methods. Alternaria, Cladosporium and Penicillium were present in both sound and damaged grapes, while Aspergillus and Botrytis were primarily found in damaged grapes. The predominant yeast species in both sound and damaged grape must, at lower and higher maturity levels, were Aureobasidium pullulans and Hanseniaspora spp. At higher grape ripening levels species diversity increased, with Hanseniaspora vineae, Metschnikowia pulcherrima and Candida membranifaciens dominating, and others such as Pichia kudriavzevii and Issatchenkia terricola appearing. A. pullulans and M. pulcherrima were highly tolerant to SO₂. Notably, the species Meyerozyma guilliermondii, Zygoascus hellenicus and Hanseniaspora uvarum were exclusively present in damaged grape must, while Zygosaccharomyces bailii was also found in sound grape must. Hanseniaspora spp. and P. kudriavzevii predominated at mid-fermentation and persisted at the end of the process, highlighting their resistance to wine conditions and their potential to influence post-fermentative dynamics. These findings emphasise the significant influence of grape sanitary status on mycobiota composition, with important implications for fermentation behaviour and final wine quality. Full article

The plant microbiome plays a pivotal role in host development and resilience against biotic and abiotic stresses. In perennial crops like peach, microbial communities inhabiting dormant buds—critical yet vulnerable organs—may influence disease outcomes and plant fitness. This study characterized the bacterial and fungal communities associated with the buds of three peach cultivars differing in susceptibility to Twig Canker and Shoot Blight (TCSB). Amplicon-based profiling revealed distinct microbiome signatures across cultivars, shaped by host genotype. The highly tolerant ‘Catherina’ harbored a structured and relatively diverse community enriched in beneficial bacterial genera such as Pseudomonas, Sphingomonas, and Curtobacterium, alongside protective yeasts including Aureobasidium and Cladosporium. In contrast, the susceptible cultivar ‘Pavoro^®-Pav 1605’ hosted a less balanced microbiome, marked by enrichment of opportunistic pathogens such as Alternaria and Diaporthe, as well as the bacterial lineage 1174-901-12. The intermediate cultivar ‘Lami^®.COM’ displayed a transitional profile enriched in Sphingomonas, Pelomonas, and Vishniacozyma. Differential abundance analyses confirmed cultivar-specific enrichment patterns, underscoring the influence of genotype in shaping microbiota composition and potential disease outcomes. These findings support the integration of microbiome-based approaches into sustainable disease management via beneficial microbial promotion, early detection of harmful consortia, and microbiome-informed breeding to foster resilient, low-input peach cultivation systems. Full article

A study was carried out to identify the filamentous fungi and yeasts present in rotten wine grapes from two subzones of the Southern oasis of Mendoza winegrowing region, to assess the occurrence of tenuazonic acid (TA), a mycotoxin produced by the Alternaria genus, and to evaluate the wine spoilage potential of the associated yeasts in vitro and during microvinifications. The main fungal genera present were Alternaria (69.3%), followed by Aspergillus (16.8%), Penicillium (9.3%), and Cladosporium (4.6%), while the dominant yeast species Metschnikowia pulcherrima (23.1%), Aureobasidium pullulans (20.2%) and Hanseniaspora uvarum (13.0%) were followed by H. vineae (11.6%), Zygosaccharomyces bailii (10.4%), and H. guilliermondii (9.2%). Additionally, 94.1% of the rotten samples were contaminated with TA, with the highest level found in the Cabernet Sauvignon variety. No geographic association was found in the incidence of the different fungal genera or yeast species, nor in the occurrence of TA. Almost all of the tested yeasts produced H₂S, the majority of the Hanseniaspora strains produced acetic acid, and only one M. pulcherrima strain produced off-flavours in in vitro tests. Wines co-fermented with H. uvarum L144 and S. cerevisiae showed higher volatile acidity and lower fruity aroma and taste intensity. Therefore, processing bunch rot could pose a toxicological and microbiological risk to winemaking due to the high incidence of Alternaria and TA, as well as the potential of the associated yeasts to spoil wine. Full article

Plums are climacteric fruits with a short postharvest shelf-life, which makes them highly susceptible to spoilage by moulds and pathogens. Biological control using antagonistic yeasts offers a promising approach to extend shelf-life by inhibiting fungal growth. This study evaluated the effects of two yeast strains, Hanseniaspora uvarum L793 and Metschnikowia pulcherrima L672, on the quality of ‘Larry Ann’ Japanese plums during cold storage. Plums were divided into three batches: two treated by immersion in yeast suspensions (10⁸ cells mL⁻¹) and one untreated control. Quality parameters assessed over 12 weeks at 1 °C included weight loss, decay index, microbial counts, yeast colonisation, skin and flesh colour, texture, pH, titratable acidity, total soluble solids, and ripening index, with evaluations every week. M. pulcherrima L672 showed strong colonisation and persistence on the plum surface, significantly reducing skin damage and mould incidence. In contrast, H. uvarum L793 initially colonised well but declined over time, being replaced by native yeasts such as Aureobasidium spp. Both treatments maintained the physicochemical and organoleptic quality of the plums throughout storage. However, M. pulcherrima L672 was more effective in suppressing fungal growth and preserving fruit integrity. These findings suggest that M. pulcherrima L672 is a promising biocontrol agent for prolonging the shelf-life of Japanese plums during cold storage, maintaining their commercial quality for up to three months. Full article

Microbial enzymes, due to their efficiency, specificity, and sustainability, are central to innovative biotechnological strategies aimed at optimizing industrial processes such as winemaking. In this study, the potential of Aureobasidium pullulans m11-2, a native dimorphic fungus from the wine ecosystem, was evaluated as a source of hydrolytic enzymes capable of degrading grape cell wall polysaccharides. The strain was identified at the molecular level and characterised in terms of its morphology. To maximise enzyme production, various culture media were tested. Among the concentrations tested, the optimal levels of glucose and pectin were 1 g L⁻¹ and 10 g L⁻¹, respectively. The partially constitutive and inducible nature of the various polysaccharidase activities (pectinases, cellulases, and xylanases) was confirmed. The effect of grape skins (a winemaking by-product) on microbial growth and enzyme synthesis was evaluated, achieving a pectinase activity of 0.622 U mL⁻¹ when combined with 1 g L⁻¹ of glucose. Maximum enzyme yields were detected during the exponential growth phase in both citrus pectin and grape skin media, suggesting favorable conditions for continuous bioprocessing. These results confirm that A. pullulans m11-2 is an interesting microbial option for producing polysaccharidases that can be adapted to sustainable production systems. Full article

Apricots are affected by many abiotic and biotic factors that could negatively impact their vitality and yield, leading to branch and tree dieback. Knowledge of the microbiome composition is key to choosing the optimal measurement strategy. The effect of the two different growing systems, i.e., organic (ORG) and integrated pest management (IPM), on the apricot fungal microbiome was studied. The inner bark was used to isolate DNA, and the present fungi were analyzed using a metagenomics high-throughput sequencing (HTS) profiling approach of the data obtained based on the Illumina sequencing of the ITS1-ITS2 amplicons of the 18S rRNA gene. Of the 20 analyzed samples, Ascomycota was the dominant phylum, and Dothiomycetes was the most abundant. Basidiomycota was the less frequent, with Tremellomycetes being the predominant within this phylum. PCA analysis showed the complete separation of the samples obtained from the orchards grown under the ORG and IPM systems. Cladosporia, Alternaria, Aureobasidium, and Visniacozyma were detected in all samples, but they dominated the IPM samples. Filobasiadiales were recognized as an indicator species for ORG management, while Caliciales, Lecanorales, Lichinales, Mycosphaerellales, Myriangiales, Phacidiales, Teloschistales, and Thelebolales were identified as indicator species for IPM management. Based on the order and genus levels, a significantly higher fungal microbiome richness was detected in the ORG samples. This could be connected to the environmentally beneficial growing system applied in the orchard, but it is impossible to assess the risk of trunk disease development or premature apricot tree decline. Full article

Tropical sandy beaches are dynamic ecosystems where microbial communities play crucial roles in biogeochemical processes and tracking human impact. Despite their importance, these habitats remain underexplored. Here, using amplicon-based sequencing of bacterial (V3-V4 16S rRNA) and fungal (ITS2) markers, we first describe microbial communities inhabiting supralittoral–intertidal sediments of two contrasting sandy beaches in the Tadjoura Gulf (Djibouti Republic): Sagallou-Kalaf (SK, rural, siliceous sand) and Siesta Plage (SP, urban, calcareous sand). Sand samples were collected at low tide along 10 m transects perpendicular to the shoreline. Bacterial communities differed significantly between sites and along the sea-to-land gradient, suggesting an influence from both anthropogenic activity and sediment granulometry. SK was dominated by Escherichia-Shigella, Staphylococcus, and Bifidobacterium, associated with human and agricultural sources. SP showed higher richness, with enriched marine-associated genera such as Hoeflea, Xanthomarina, and Marinobacter, also linked to hydrocarbon degradation. Fungal diversity was less variable, but showed significant shifts along transects. SK communities were dominated by Kluyveromyces and Candida, while SP hosted a broader fungal assemblage, including Pichia, Rhodotorula, and Aureobasidium. The higher richness at SP suggests that calcium-rich sands, possibly due to their buffering capacity and greater moisture retention, offer more favorable conditions for microbial colonization. Full article

Winemaking involves a microbial ecosystem where yeast diversity, shaped by terroir and winemaking conditions, determines wine characteristics. Understanding the microbial diversity of vineyards and spontaneous fermentation is crucial for explaining a winery’s typical wine profile. Studying and inoculating indigenous strains make it possible to produce high quality wines, reflecting the production environment. This study analyzes the yeast species involved in 16 spontaneous fermentations (8 in 2022 and 8 in 2023) from grapes of four distinct vineyards under two sets of winemaking conditions. A total of 1100 yeast colonies were identified by MALDI-TOF and DNA sequencing techniques. Saccharomyces (S.) cerevisiae and Hanseniaspora uvarum were the most prevalent species, alongside significant populations of non-Saccharomyces yeasts such as Lachancea thermotolerans and Metchnikowia pulcherrima, which were the most abundant ones. Minor yeast species, including Aureobasidium pullulans, Starmerella bacillaris, Kazachstania servazzi, and other Hanseniaspora spp., were also detected. The results demonstrated that yeast diversity in spontaneous fermentations varied according to vineyard origin and winemaking conditions. Differences between the two vintages studied indicated that annual climatic conditions significantly influenced yeast diversity, especially among non-Saccharomyces species. This substantial diversity represents a valuable source of indigenous yeasts for preserving the typicity of a winery’s wines under controlled conditions. Full article