Proteomic approach to unveil the ochratoxin A repression by Debaryomyces hansenii and rosemary on Penicillium nordicum during dry-cured fermented sausages ripening

Mechanisms of action of bioprotective plant extracts against the ochratoxigenic Penicillium nordicum in dry-cured sausages

Plant extracts are promising strategies to minimise the hazard associated with ochratoxin A (OTA) in dry-cured sausages. Nonetheless, their mechanisms have not been elucidated yet. The mechanisms by which rosemary (REO), thyme (TEO) and oregano (OEO) essential oils and the extract of acorn shell (AE) impact on the OTA production by Penicillium nordicum were evaluated. Their effect on the mould's gene expression, ergosterol synthesis, reactive oxygen species (ROS) production and spore germination and their potential to the OTA detoxification were in vitro studied in three mould strains. Differences at sampling time, plant extract and mould strain levels were found for all mechanisms of the antifungal agents. The relative expression of Hog1 and Rho1 genes were less affected than that of the otanps and otapks genes in treated moulds compared to the non-treated control. All treatments were able to decrease ergosterol production against one strain. Furthermore, REO 500 μL/mL, AE and OEO 50 μL/mL produced the highest fluorescence associated with ROS for another strain at the end of the incubation. Moreover, a significant detoxification of the plant extracts was only found for OEO 50 μL/mL after 24 h of incubation. Besides, spore germination was totally inhibited by TEO and OEO, obtaining the opposite effect for AE. No clear relationship was found when those findings were correlated to the OTA accumulation. Consequently, the antiochratoxigenic effect of plant extracts seems to be due to the involvement of several mechanisms of action. Finally, the plant extracts did not inhibit the potentially protective cultures against ochratoxigenic moulds.

Untargeted metabolomics to relate changes produced by biocontrol agents against Aspergillus westerdijkiae and Penicillium nordicum in vitro on dry-cured ham

Dry-cured ham is a highly appreciated meat product. During the ripening, moulds grow on its surface such as Penicillium nordicum and Aspergillus westerdijkiae producers of ochratoxin A (OTA). This mycotoxin poses a risk to consumers that must be controlled. The aim of this work is to evaluate the effectiveness of Debaryomyces hansenii and Staphylococcus xylosus isolated from dry-cured ham as a combined biocontrol culture (BCA) to reduce the OTA produced by one strain of A. westerdijkiae and two strain of P. nordicum, and to assess the metabolomic changes they cause. Each mould was inoculated alone and in combination with BCA on dry-cured ham for 14 days at 20 °C. OTA and total metabolites were analysed in a mass spectrometer Orbitrap Q- Exactive Plus. The Compound Discoverer software, in-house Python-based software and the Metaboanalyst software were used for metabolite analysis. BCA reduced the OTA of A. westerdijkiae, P. nordicum 15 and P. nordicum 856 by 78 %, 99 % and 65 % respectively. BCA caused changes in their metabolome, mainly in the phenylalanine metabolism pathway altering compounds such as Phenylacetaldehyde, Phenylpyruvate or trans-2-hydroxycinnamate, the synthesis of phenylalanine, tyrosine, and tryptophan altering compounds such as 4-hydroxyphenylpyruvate or L-tryptophan, and in the synthesis of oxylipins derived from the linoleic acid metabolism such as 13-OxoODE, 9(S)-HODE or 9(10)-EpOME.

Deciphering the antiochratoxigenic activity of plant extracts and Debaryomyces hansenii against Penicillium nordicum in a "chorizo"-based medium by proteomic analysis

Penicillium nordicum is the main ochratoxin A (OTA)-producing species on the surface of dry-fermented sausages, such as the "chorizo". New antifungal strategies are being developed using biocontrol agents (BCAs), such as plant extracts and native microorganisms. This work aimed to evaluate the antiochratoxigenic capacity and the causative modes of action of BCAs (rosemary essential oil (REO), acorn shell extract and the yeast Debaryomyces hansenii (Dh)) in a "chorizo"-based medium (Ch-DS). BCAs were inoculated on Ch-DS together with P. nordicum and incubated at 12 °C for 15 days to collect mycelia for OTA analyses and comparative proteomics. Both REO and Dh alone decreased OTA accumulation up to 99% and affected the abundance of P. nordicum proteins linked to cell wall organisation, synthesis of OTA-related metabolites and ergosterol synthesis. It is worth highlighting the increased abundance of an amidase by REO, matching with the decrease in OTA. The use of REO and Dh as BCAs could be an effective strategy to reduce the OTA hazard in the meat industry. Based on their not fully coincident modes of action, their combined application could be of interest in "chorizo" to maximise their potential against ochratoxigenic strains.

Unravelling the effect of control agents on Gnomoniopsis smithogilvyi on a chestnut-based medium by proteomics

BACKGROUND

Gnomoniopsis smithogilvyi is the major chestnut pathogen, responsible for economic losses and recently described as a 3-nitropropionic acid and diplodiatoxin mycotoxin producer. Bacillus amyloliquefaciens QST 713 (Serenade® ASO), B. amyloliquefaciens CIMO-BCA1, and the fungicide Horizon® (tebuconazole) have been shown to reduce the growth of G. smithogilvyi. However, they enhanced mycotoxin production. Proteomics can clarify the mould's physiology and the impact of antifungal agents on the mould's metabolism. Thus, the aim of this study was to assess the impact of Horizon®, Serenade®, and B. amyloliquefaciens CIMO-BCA1 in the proteome of G. smithogilvyi to unveil their modes of action and decipher why the mould responds by increasing the mycotoxin production. For this, the mycelium close to the inhibition zone provoked by antifungals was macroscopically and microscopically observed. Proteins were extracted and analysed using a Q-Exactive plus Orbitrap.

RESULTS

The results did not elucidate specific proteins involved in the mycotoxin biosynthesis, but these agents provoked different kinds of stress on the mould, mainly affecting the cell wall structures and antioxidant response, which points to the mycotoxins overproduction as a defence mechanism. The biocontrol agent CIMO-BCA1 acts similar to tebuconazole. The results revealed different responses on the mould's metabolism when co-cultured with the two B. amyloliquefaciens, showing different modes of action of each bacterium, which opens the possibility of combining both biocontrol strategies.

CONCLUSION

These results unveil different modes of action of the treatments that could help to reduce the use of toxic chemicals to combat plant pathogens worldwide. © 2023 Society of Chemical Industry.

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.

Effect of selected agents for ochratoxin A biocontrol on the colour, texture and volatile profile of dry-cured fermented sausages

BACKGROUND

Traditional dry-cured fermented sausages favour the growth of an autochthonous microbial population, which plays an important role in their sensory aspects. However, some moulds can produce mycotoxins such as ochratoxin A (OTA). The biocontrol agents (BCAs) Debaryomyces hansenii FHSCC 253H and Staphylococcus xylosus FHSCC Sx8 have been demonstrated to reduce OTA production in dry-cured meat products, but their influence in the sensory characteristics of sausages has to be tested. The aim of this study was to evaluate the effect of these BCAs on the colour, texture and volatile profile of dry-cured fermented sausages.

RESULTS

D. hansenii caused few differences in the tested parameters with respect to the control batch. S. xylosus modified the texture and colour, although the values found were within the range expected for dry-cured fermented sausages 'salchichón'. Additionally, the volatile profile revealed the potential antioxidant effect of both BCAs and their ability to produce compounds associated with the ripened aroma that could increase product acceptability.

CONCLUSION

The results indicate that there were no inconveniences in implementing both BCAs during the processing of dry-cured fermented sausages 'salchichón'. Moreover, D. hansenii FHSCC 253H could improve the volatile profile of this product. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Deciphering Staphylococcus xylosus and Staphylococcus equorum mode of action against Penicillium nordicum in a dry-cured ham model system

Penicillium nordicum is one of the major producers of ochratoxin A (OTA) in dry-cured ham. Staphylococcus xylosus Sx8 and Staphylococcus equorum Se31 have been previously proposed as biocontrol agents (BCAs) to prevent the OTA contamination, although their antifungal mode of action has not been established yet. Thus, the aim of this work was to elucidate their mode of action against P. nordicum in a dry-cured ham model system. For this, the effect of live cells, dead cells, and cell-free broth; the nutritional utilisation pattern, niche overlap index (NOI), interactions by dual-culture assays, antifungal effect of volatile compounds, OTA detoxification, and effect on fungal proteome were determined. No fungal growth was observed after 14 days of co-culture with live cells of each staphylococcus at 15 or 20 °C. However, such inhibition was not observed with either dead cells or extracellular extracts. The number of carbon sources utilised by P. nordicum was higher than those used by both cocci at 20 °C, whilst the opposite occurred at 15 °C. According to NOI, nutritional dominance depends on temperature, at 20 °C P. nordicum dominated the niche, but at 15 °C the mould is dominated by the BCAs. The volatile pattern generated by each coccus did not show antifungal effect, and both staphylococci failed to degrade or adsorb OTA. However, in the interaction assay, S. xylosus and S. equorum were able to decrease the fungal growth and its OTA production. In addition, proteomic analyses showed changes in the abundance of proteins related to the cell wall integrity (CWI), carbohydrate metabolism and the biosynthesis of secondary metabolites such as OTA. In conclusion, overall, the antagonistic effects of the two studied cocci against P. nordicum are greater at 15 °C than at 20 °C, being linked to competition for space and nutrients, triggering alterations in CWI pathway, OTA biosynthesis, and carbohydrate metabolism.

Traditional Meat Products-A Mycotoxicological Review

Traditional meat products are commonly produced in small family businesses. However, big industries are also involved in the production of this kind of product, especially since a growing number of consumers crave the traditional taste and aromas. The popularization of original and organic products has resulted in a return to traditional production methods. Traditional meat products are produced worldwide. However, in such (domesticated) conditions there is a potential danger for mycotoxin contamination. This review aims to present the sources of mycotoxins in traditional meat products, the most common mycotoxins related to such meat products, and future prospects regarding the suppression of their occurrence. Special attention should be paid to reducing the transfer of mycotoxins via the food chain from animal feed to animals to humans (stable-to-table principle), which is also described in this review. Other sources of mycotoxins (spices, environment, etc.) should also be monitored for mycotoxins in traditional production. The importance of monitoring and regulating mycotoxins in meat products, especially in traditional meat products, is slowly being recognized by the institutions and hopefully, in the future, can deliver legally regulated limits for such products. This is especially important since meat products are available to the general population and can seriously affect human health.

Proteomic analyses of Bacteroides ovatus and Bifidobacterium longum in xylan bidirectional culture shows sugar cross-feeding interactions

The intestinal microbiome is a community of anaerobic microorganisms whose activities significantly impact human health. Its composition can be modulated by consuming foods rich in dietary fiber, such as xylan, a complex polysaccharide that can be considered an emerging prebiotic. In this work, we evaluated how certain gut bacteria acted as primary degraders, fermenting dietary fibers, and releasing metabolites that other bacteria can further use. Different bacterial strains of Lactobacillus, Bifidobacterium, and Bacteroides were evaluated for their ability to consume xylan and interact with one another. Results from unidirectional assays gave indications of possible cross-feeding between bacteria using xylan as a carbon source. Bidirectional assays showed that Bifidobacterium longum PT4 increased its growth in the presence of Bacteroides ovatus HM222. Proteomic analyses indicated that B. ovatus HM222 synthesizes enzymes facilitating xylan degradation, such as β-xylanase, arabinosidase, L-arabinose isomerase, and xylosidase. Interestingly, the relative abundance of these proteins remains largely unaffected in the presence of Bifidobacterium longum PT4. In the presence of B. ovatus, B. longum PT4 increased the production of enzymes such as α-L-arabinosidase, L-arabinose isomerase, xylulose kinase, xylose isomerase, and sugar transporters. These results show an example of positive interaction between bacteria mediated by xylan consumption. Bacteroides degraded this substrate to release xylooligosaccharides, or monosaccharides (xylose, arabinose), which might support the growth of secondary degraders such as B. longum.

Bio-based material-edible rosemary induced biodegradation of aflatoxin B1 via altering endogenous protective enzymes signatures in animal-derived foods

Aflatoxin B1 (AFB1) is the most hazardous mycotoxin, posing risks to public health. Utilization of bio-based materials to biodegrade AFB1 is a green strategy to overcome this issue. The investigation aimed to screen for endogenous protective enzymes in bio-based material-edible rosemary based on ultra-high performance liquid chromatography coupled to hybrid quadrupole-Orbitrap high-resolution mass spectrometry (UHPLC-Q-Orbitrap HRMS)-proteomics and ascertain their impacts on the biodegradation and biotransformation of AFB1, and the trade-offs of multilevel metabolism of the animal-derived foods through untargeted metabolomics. The proteomics results verified that bio-based material-edible rosemary (0.20%, w/w) significantly up-regulated glutathione S-transferase and stimulated the down-regulation of cytochrome P450 1A2 levels via activating AhR nuclear translocation in rosemary-pickled AFB1-contaminated goat meat. Metabolomics results demonstrated that edible rosemary substantially increased histidine and glutathione implicated in the antioxidant status of goat meat. More importantly, edible rosemary with high endogenous protective enzyme content could efficiently biodegrade AFB1 in goat meat. We first unveiled that rosemary could not only efficiently biodegrade AFB1 up to 90.20% (20.00-1.96 μg kg^-1) but also elevate the bio-ingestion quality of goat meat. These findings suggest that the bio-based material-rosemary is an efficient and environmentally friendly approach for biodegrading AFB1 and elevating the bio-ingestion composition of goat meat.

Perspectives on the Probiotic Potential of Indigenous Moulds and Yeasts in Dry-Fermented Sausages

The role of indigenous fungi in the appropriate development of sensory properties and the safety of dry-fermented sausages has been widely established. Nonetheless, their applications as probiotic agents have not been elucidated in such products yet, despite their promising functional features. Thus, it should be interesting to evaluate the probiotic potential of native Debaryomyces hansenii isolates from dry-fermented sausages and their application in the meat industry, because it is the most frequently isolated yeast species from these foodstuffs and its probiotic effects for animals as well as its possible probiotic activity for human beings have been demonstrated. Within the functional ability of foodborne yeasts, anti-inflammatory, antioxidant, antimicrobial, antigenotoxic, and immunomodulatory properties have been reported. Similarly, the use of dry-fermented sausages as vehicles for probiotic moulds remains a challenge because the survival and development of moulds in the gastrointestinal tract are still unknown. Nevertheless, some moulds have been isolated from faeces possibly from their spores as a form of resistance. Additionally, their beneficial effects on animals and humans, such as the decrease in lipid content and the anti-inflammatory activity, have been reported, although they seem to be more related to their postbiotic capacity due to the generated bioactive compounds with profunctional attributes than to their role as probiotics. Therefore, further studies providing knowledge useful for generating dry-fermented sausages with improved functionality are fully necessary.

Biocontrol of Pathogen Microorganisms in Ripened Foods of Animal Origin

Ripened foods of animal origin comprise meat products and dairy products, being transformed by the wild microbiota which populates the raw materials, generating highly appreciated products over the world. Together with this beneficial microbiota, both pathogenic and toxigenic microorganisms such as Listeria monocytogenes, Salmonella enterica, Staphylococcus aureus, Clostridium botulinum, Escherichia coli, Candida spp., Penicillium spp. and Aspergillus spp., can contaminate these products and pose a risk for the consumers. Thus, effective strategies to hamper these hazards are required. Additionally, consumer demand for clean label products is increasing. Therefore, the manufacturing sector is seeking new efficient, natural, low-environmental impact and easy to apply strategies to counteract these microorganisms. This review gathers different approaches to maximize food safety and discusses the possibility of their being applied or the necessity of new evidence, mainly for validation in the manufacturing product and its sensory impact, before being implemented as preventative measures in the Hazard Analysis and Critical Control Point programs.

Effect of fermentation methods on the quality and in vitro antioxidant properties of Lycium barbarum and Polygonatum cyrtonema compound wine

Lycium barbarum and Polygonatum cyrtonema are known for their medicinal, edible, and ornamental properties. The sensory indices of the novel high-quality L. barbarum and P. cyrtonema compound wine (LPCW) fermented by Saccharomyces cerevisiae RW and Debaryomyces hansenii AS2.45 under different inoculation methods were analyzed. The alcohol content of the LPCW ranged from 3.88 to 4.75 % under three mixed inoculations. The total saponin and total polysaccharide contents in LPCW inoculated with D. hansenii first and S. cerevisiae after 24 h were 4.39 mg/mL and 0.21 mg/mL, respectively. Ethyl butyrate, citronellol, and 3-(methylthio) propanol were unique metabolites of D. hansenii. 4-Methoxybenzoic acid was the core product of brewing of by S. cerevisiae. Except for wine inoculated with S. cerevisiae only, the acceptability scores of all the LPCW samples were higher than 7.3. Our data provided the foundation for the development and application of medicinal and food homologous substances in food fermentation.

The potential of proteomics in the study of processed meat products

Proteomics is a field that has grown rapidly since its emergence in the mid-1990s, reaching many disciplines such as food technology. The application of proteomic techniques in the study of complex biological samples such as foods, specifically meat products, allows scientists to decipher the underlying cellular mechanisms behind different quality traits. Lately, much emphasis has been placed on the discovery of biomarkers that facilitate the prediction of biochemical transformations of the product and provide key information on parameters associated with traceability and food safety. This review study focuses on the contribution of proteomics in the improvement of processed meat products. Different techniques and strategies have recently been successfully carried out in the study of the proteome of these products that can help the development of foods with a higher sensory quality, while ensuring consumer safety through early detection of microbiological contamination and fraud. SIGNIFICANCE: The food industry and the academic world work together with the aim of responding to market demands, always seeking excellence. In particular, the meat industry has to face a series of challenges such as, achieving sensory attributes in accordance with the standards required by the consumer and maintaining a high level of safety and transparency, avoiding deliver adulterated and/or contaminated products. This review work exposes how the aforementioned challenges are attempted to be solved through proteomic technology, discussing the latest and most outstanding research in this regard, which undoubtedly contribute to improving the quality, in all the extension of the word, of meat products, providing relevant knowledge in the field of proteomic research.

Mycotoxins and Essential Oils-From a Meat Industry Hazard to a Possible Solution: A Brief Review

The preservation of food supplies has been humankind's priority since ancient times, and it is arguably more relevant today than ever before. Food sustainability and safety have been heavily prioritized by consumers, producers, and government entities alike. In this regard, filamentous fungi have always been a health hazard due to their contamination of the food substrate with mycotoxins. Additionally, mycotoxins are proven resilient to technological processing. This study aims to identify the main mycotoxins that may occur in the meat and meat products "Farm to Fork" chain, along with their effect on the consumers' health, and also to identify effective methods of prevention through the use of essential oils (EO). At the same time, the antifungal and antimycotoxigenic potential of essential oils was considered in order to provide an overview of the subject. Targeting the main ways of meat products' contamination, the use of essential oils with proven in vitro or in situ efficacy against certain fungal species can be an effective alternative if all the associated challenges are addressed (e.g., application methods, suitability for certain products, toxicity).