Enhancement of Biocontrol Efficacy of Pichia kudriavzevii Induced by Ca Ascorbate against Botrytis cinerea in Cherry Tomato Fruit and the Possible Mechanisms of Action

Addressing the Concern of Orange-Yellow Fungus Growth on Palm Kernel Cake: Safeguarding Dairy Cattle Diets for Mycotoxin-Producing Fungi

Palm kernel cake (PKC), a byproduct of palm oil extraction, serves an important role in Ecuador's animal feed industry. The emergence of yellow-orange fungal growth in PKC on some cattle farms in Ecuador sparked concerns within the cattle industry regarding a potential mycotoxin-producing fungus on this substrate. Due to the limited availability of analytical chemistry techniques in Ecuador for mycotoxin detection, we chose to isolate and identify the fungus to determine its association with mycotoxin-producing genera. Through molecular identification via ITS region sequencing, we identified the yellow-orange fungus as the yeast Candida ethanolica. Furthermore, we isolated two other fungi-the yeast Pichia kudriavzevii, and the fungus Geotrichum candidum. Molecular identification confirmed that all three species are not classified as mycotoxin-producing fungi but in contrast, the literature indicates that all three have demonstrated antifungal activity against Aspergillus and Penicillium species, genera associated with mycotoxin production. This suggests their potential use in biocontrol to counter the colonization of harmful fungi. We discuss preventive measures against the fungal invasion of PKC and emphasize the importance of promptly identifying fungi on this substrate. Rapid recognition of mycotoxin-producing and pathogenic genera holds the promise of mitigating cattle intoxication and the dissemination of mycotoxins throughout the food chain.

Towards unlocking the biocontrol potential of Pichia kudriavzevii for plant fungal diseases: in vitro and in vivo assessments with candidate secreted protein prediction

BACKGROUND

Plant fungal pathogens cause substantial economic losses through crop yield reduction and post-harvest storage losses. The utilization of biocontrol agents presents a sustainable strategy to manage plant diseases, reducing the reliance on hazardous chemical. Recently, Pichia kudriavzevii has emerged as a promising biocontrol agent because of its capacity to inhibit fungal growth, offering a potential solution for plant disease management.

RESULTS

Two novel Pichia kudriavzevii strains, Pk_EgyACGEB_O1 and Pk_EgyACGEB_O2, were isolated from olive brine samples. The microscopic characterization of the strains revealed similar structures. However, there were noticeable differences in their visual morphology. Based on their internal transcribed spacer (ITS) DNA sequences, Pk_EgyACGEB_O1 and Pk_EgyACGEB_O2 strains assigned by GenBank IDs MZ507552.1 and MZ507554.1 shared high sequence similarity (~ 99.8% and 99.5%) with P. kudriavzevii, respectively. Both strains were evaluated in vitro against plant pathogenic fungi. The strains revealed the ability to consistently inhibit fungal growth, with Pk_EgyACGEB_O2 showing higher effectiveness. In addition, both P. kudriavzevii strains effectively controlled grey mold disease caused by B. cinerea in golden delicious apples, suggesting their potential as sustainable and eco-friendly biocontrol agents for post-harvest diseases. Based on a comprehensive bioinformatics pipeline, candidate-secreted proteins responsible for the potent antifungal activity of P. kudriavzevii were identified. A total of 59 proteins were identified as common among the P. kudriavzevii CBS573, SD108, and SD129 strains. Approximately 23% of the secreted proteins in the P. kudriavzevii predicted secretome are hydrolases with various activities, including proteases, lipases, glycosidases, phosphatases, esterases, carboxypeptidases, or peptidases. In addition, a set of cell-wall-related proteins was identified, which might enhance the biocontrol activity of P. kudriavzevii by preserving the structure and integrity of the cell wall. A papain inhibitor was also identified and could potentially offer a supplementary defense against plant pathogens.

CONCLUSION

Our results revealed the biocontrol capabilities of P. kudriavzevii against plant pathogenic fungi. The research focused on screening novel strains for their ability to inhibit the growth of common pathogens, both in vitro and in vivo. This study shed light on how P. kudriavzevii interacts with fungal pathogens. The findings can help develop effective strategies for managing plant diseases.

Improvement of shelf-life of cherry (Prunus avium L.) by combined application of modified-atmosphere packaging and antagonistic yeast for long-distance export

BACKGROUND

The last decade has seen a growing interest in reducing the use of chemical fungicides for postharvest decay control. In the research for new, safe alternatives, the combined application of biocontrol agents and passive modified-atmosphere packaging (MAP) has been shown to be a promising strategy to extend fruit quality. Therefore, the aim of this work was to evaluate the effect of the combined application of MAP and two antagonistic yeasts, Metschnikowia pulcherrima L672 and Pichia kudriavzevii PK18, on sweet cherry shelf life.

RESULTS

Microbiological, physico-chemical, and quality fruit analysis from batches treated with antagonistic yeast were compared with a control batch without yeast application and a batch to which fludioxonil (Scholar®) was applied. The composition of the atmosphere and physico-chemical traits showed similar values among the different batches during cold storage. However, interestingly, the combination of MAP with the antagonistic yeasts M. pulcherrima L672 and P. kudriavzevii PK18 increases the control of microbiological spoilage with results comparable to the application of fludioxonil. In addition, these batches experienced a slight decrease in volatile compounds associated with fresh fruit aroma, whereas in the control batch an increase of altered fruit aromas was observed. The same effect of control of spoilage was observed during the shelf life period.

CONCLUSION

These results showed the positive effect of the combination of antagonistic yeasts and MAP, obtaining similar results in terms of control of microbiological spoilage and physico-chemical quality compared with the application of fludioxonil. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Advances in the Application of the Non-Conventional Yeast Pichia kudriavzevii in Food and Biotechnology Industries

Pichia kudriavzevii is an emerging non-conventional yeast which has attracted increased attention for its application in food and biotechnology areas. It is widespread in various habitats and often occurs in the spontaneous fermentation process of traditional fermented foods and beverages. The contributions of P. kudriavzevii in degrading organic acid, releasing various hydrolase and flavor compounds, and displaying probiotic properties make it a promising starter culture in the food and feed industry. Moreover, its inherent characteristics, including high tolerance to extreme pH, high temperature, hyperosmotic stress and fermentation inhibitors, allow it the potential to address technical challenges in industrial applications. With the development of advanced genetic engineering tools and system biology techniques, P. kudriavzevii is becoming one of the most promising non-conventional yeasts. This paper systematically reviews the recent progress in the application of P. kudriavzevii to food fermentation, the feed industry, chemical biosynthesis, biocontrol and environmental engineering. In addition, safety issues and current challenges to its use are discussed.