Exploring yeast-based microbial interactions: The next frontier in postharvest biocontrol

Advances and perspectives in biological control of postharvest fungal decay in citrus fruit utilizing yeast antagonists

Citrus fruits are one of the most highly grown fruit crops worldwide. A significant production problem, however, is their susceptibility to postharvest decay, caused by fungi such as Penicillium spp., resulting in significant losses in marketable yield. Some fungal species also produce mycotoxins that are potentially harmful to humans. Biological control of postharvest decay in citrus utilizing yeast antagonists has been shown to be a promising alternative to the use of synthetic fungicides to address increasingly stringent government regulatory policies and consumer demands. In this current review, we provide an overview of the research conducted on major postharvest decay fungi and their impact on the citrus industry. Then, the isolation and application of yeast antagonists used to manage postharvest decay in citrus is discussed, as well as their mechanisms of action, such as an oxidative burst of reactive oxygen species (ROS), iron depletion, and secondary metabolites. Lastly, the application of recent approaches (e.g., CRISPR/Cas9, RNAi, -omics technologies) in the study of citrus postharvest diseases is reviewed. For biological control to reach its full potential as a key component of an integrated disease management strategy for citrus, additional research will be required to explore the potential use of beneficial microbial consortia. The consortia will need to be comprised of individual core microbial species present in and on citrus fruit throughout its development and that metabolically complement each other in an interacting network.

Eco-friendly biocontrol strategies for management of postharvest fungal decays in kiwifruit: A review

Kiwifruit is known for its rich content of nutrients and significant economic value. Global cultivation of kiwifruit has been increasing along with the amount of land being dedicated to its production. Regrettably, postharvest fungal decays, such as those caused by Botrytis cinerea, Penicillium expansum, Alternaria alternata, Botryosphaeria dothidea, Nigrospora oryzae, and others, pose a significant challenge to the kiwifruit industry, and are responsible for substantial losses during storage, transportation, and local marketing. Biological control of postharvest diseases is seen as a safe and sustainable strategy and as a result has received considerable interest for its potential in disease management. The present review provides an overview of the research conducted on the major postharvest diseases of kiwifruit and the use of biocontrol agents to manage these diseases. It also reviews the status of microbial formulations and the impact of environmental factors on biocontrol efficacy. The need for further research on the utilization of microbial consortia to manage postharvest diseases of kiwifruit is discussed as a major new approach to biological control.

Isolation of an endophytic yeast for improving the antibacterial activity of water chestnut Jiaosu: Focus on variation of microbial communities

Recent years have seen an increase in the development of functional Jiaosu products, including eco-friendly Jiaosu and antimicrobial healthcare fermentation products. As a result, research on the antibacterial activity of Jiaosu has attracted attention. In the present study, the endophytic yeast WCF016, which exhibits antibacterial activity against Escherichia coli and Staphylococcus aureus, was isolated from the peel of water chestnut and identified as Candida sake via morphological and phylogenetic analyses based on 26S rDNA D1/D2 region sequencing. Water chestnut Jiaosu with or without WCF016 inoculation exhibited similar flavor and physicochemical properties. However, inoculation significantly enhanced the antibacterial activity of water chestnut Jiaosu, especially in group D (inoculate of both fruit and vegetable enzyme starter and WCF016), which showed the largest diameter in its inhibition zone for both E. coli and S. aureus, reaching 25 ± 0 mm and 24 ± 1.0 mm. Moreover, inoculation with WCF016 influenced the abundance of the microbial community, especially Lactiplantibacillus and Zygoascus, which reached 51.76 % and 24.46 %, respectively, in group B (inoculated WCF016), thereby improving the antibacterial activity and flavor quality of the water chestnut Jiaosu. Notably, final pH, total sugar, and all organic acids effectively promoted fungal diversity and exhibited a positive correlation with most of the fungal genera. These results indicate that conditions conducive to the formation of organic acid-producing microbes and the synthesis of organic acids promote the antibacterial activity of Jiaosu.

Profiles of Killer Systems and Volatile Organic Compounds of Rowanberry and Rosehip-Inhabiting Yeasts Substantiate Implications for Biocontrol

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.

A Comprehensive Review of the Diversity of Fungal Secondary Metabolites and Their Emerging Applications in Healthcare and Environment

Fungi and their natural products, like secondary metabolites, have gained a huge demand in the last decade due to their increasing applications in healthcare, environmental cleanup, and biotechnology-based industries. The fungi produce these secondary metabolites (SMs) during the different phases of their growth, which are categorized into terpenoids, alkaloids, polyketides, and non-ribosomal peptides. These SMs exhibit significant biological activity, which contributes to the formulation of novel pharmaceuticals, biopesticides, and environmental bioremediation agents. Nowadays, these fungal-derived SMs are widely used in food and beverages, for fermentation, preservatives, protein sources, and in dairy industries. In healthcare, it is being used as an antimicrobial, anticancer, anti-inflammatory, and immunosuppressive drug. The usage of modern tools of biotechnology can achieve an increase in demand for these SMs and large-scale production. The present review comprehensively analyses the diversity of fungal SMs along with their emerging applications in healthcare, agriculture, environmental sustainability, and nutraceuticals. Here, the authors have reviewed the recent advancements in genetic engineering, metabolic pathway manipulation, and synthetic biology to improve the production and yield of these SMs. Advancement in fermentation techniques, bioprocessing, and co-cultivation approaches for large-scale production of SMs. Investigators further highlighted the importance of omics technologies in understanding the regulation and biosynthesis of SMs, which offers an understanding of novel applications in drug discovery and sustainable agriculture. Finally, the authors have addressed the potential for genetic manipulation and biotechnological innovations for further exploitation of fungal SMs for commercial and environmental benefits.

Synthetic Microbial Community Members Interact to Metabolize Caproic Acid to Inhibit Potato Dry Rot Disease

The potato dry rot disease caused by Fusarium spp. seriously reduces potato yield and threatens human health. However, potential biocontrol agents cannot guarantee the stability and activity of biocontrol. Here, 18 synthetic microbial communities of different scales were constructed, and the synthetic microbial communities with the best biocontrol effect on potato dry rot disease were screened through in vitro and in vivo experiments. The results show that the synthetic community composed of Paenibacillus amylolyticus, Pseudomonas putida, Acinetobacter calcoaceticus, Serratia proteamaculans, Actinomycetia bacterium and Bacillus subtilis has the best biocontrol activity. Metabolomics results show that Serratia protoamaculans interacts with other member strains to produce caproic acid and reduce the disease index to 38.01%. Furthermore, the mycelial growth inhibition after treatment with caproic acid was 77.54%, and flow cytometry analysis showed that the living conidia rate after treatment with caproic acid was 11.2%. This study provides potential value for the application of synthetic microbial communities in potatoes, as well as the interaction mechanisms between member strains of synthetic microbial communities.

Bioprotective yeasts: Potential to limit postharvest spoilage and to extend shelf life or improve microbial safety of processed foods

Yeasts are a widespread group of microorganisms that are receiving increasing attention from scientists and industry. Their diverse biological activities and broad-spectrum antifungal activity make them promising candidates for application, especially in postharvest biocontrol of fruits and vegetables and food biopreservation. The present review focuses on recent knowledge of the mechanisms by which yeasts inhibit pathogenic fungi and/or spoilage fungi and bacteria. The main mechanisms of action of bioprotective yeasts include competition for nutrients and space, synthesis and secretion of antibacterial compounds, mycoparasitism and the secretion of lytic enzymes, biofilm formation, quorum sensing, induced systemic resistance of fruit host, as well as the production of reactive oxygen species. Preadaptation of yeasts to abiotic stresses such as cold acclimatization and sublethal oxidative stress can improve the effectiveness of antagonistic yeasts and thus more effectively play biocontrol roles under a wider range of environmental conditions, thereby reducing economic losses. Combined application with other antimicrobial substances can effectively improve the efficacy of yeasts as biocontrol agents. Yeasts show great potential as substitute for chemical additives in various food fields, but their commercialization is still limited. Hence, additional investigation is required to explore the prospective advancements of yeasts in the field of biopreservation for food.

Can we control potato fungal and bacterial diseases? - microbial regulation

The potato plant is one of the main crops in the world. However, relatively little is known about key virulence factors of major fungal and bacterial diseases in potatoes, biocontrol measures to improve activity and stability, and the core driving forces in the control process. Here, we focus on analyzing the mechanisms by which genes, proteins, or (and) metabolites of potato pathogens as key virulence factors. Then, the single strain biocontrol agents, synthetic microbial communities, microbial microcapsule strategies were introduced, and the latter two strategies can improve stability and activity in biocontrol. Meanwhile, summarized the defense mechanisms of biocontrol and their specific issues in practical applications. Furthermore, explore how potato crop management, soil management, and climate effects, as crucial driving forces affect potato biocontrol in the system. Dynamic and systematic research, excavation of biocontrol strain resources, find the causes of regional disease resistance and exploration of biocontrol mechanism will provide promising solutions for biotic stress faced by potato in the future.