Evaluation of growth and ochratoxin A production by Aspergillus steynii and Aspergillus westerdijkiae in green-coffee based medium under different environmental conditions

Resilience to Climate Change by Biocontrol Yeasts Against Ochratoxin A Production in Robusta Coffee

Aspergillus carbonarius is the main producer of Ochratoxin A (OTA) in coffee. In the last few years, there has been an increasing interest in using yeast isolates as Biocontrol Agents to prevent OTA production in coffee cherries during the primary postharvest processing. Little is known about how climate change abiotic conditions of increased temperature (+2-4 °C), elevated CO2 (existing levels of 400 vs. 1000 ppm), and increased drought stress will impact biocontrol resilience. This study examined the effect of a three-way interaction between temperature (27, 30, and 33 °C) x water activity (aw) (0.90 and 0.95 aw) x CO2 level (400 vs. 1000 ppm) on the growth and OTA production of A. carbonarius and the resilience of three yeast strains' biocontrol capacity on fresh coffee cherries. High aw (0.95), CO2, and temperature levels increased the production of OTA by A. carbonarius. All the yeast biocontrol strains significantly reduced A. carbonarius growth by at least 20% and OTA production by up to 85%. From the three strains used, the Meyerozyma caribbica strain (Y4) showed the best resilience to climate change, since it reduced both growth (50%) and OTA production (70%) under future scenarios of CO2 and aw at all temperatures tested, and should be the one selected for pilot scale experiments in Ivory Coast.

Inhibition of Aspergillus spp. growth and ochratoxin A production in Conilon and Arabica coffees based-medium by Saccharomyces cerevisiae

Saccharomyces cerevisiae CCMA 0159 is reported as a promising biocontrol agent against ochratoxin A (OTA)-producing fungi in coffee. Coffea arabica and Coffea canephora (var. Conilon or Robusta) are the most widely consumed coffee species around the world, cultivated in tropical and subtropical regions, each exhibiting distinct physicochemical and sensory characteristics. The objective of this study was to compare the growth and OTA production by Aspergillus carbonarius, A. ochraceus, and A. westerdijkiae in C. arabica and C. canephora, along with assessing the efficiency of S. cerevisiae CCMA 0159 in biocontrolling ochratoxigenic fungi in both coffee varieties. A. carbonarius exhibited a higher growth rate and OTA production in both coffee varieties, with C. canephora showing particular susceptibility. Conversely, A. ochraceus and A. westerdijkiae demonstrated lower growth and OTA production. S. cerevisiae was effective in biocontrolling the fungal isolates, inhibiting over 80 % of A. carbonarius growth in both coffee varieties. Among the mechanisms of action of the biological control agent, the production of volatile organic compounds stands out. The results of this study confirm the significant potential of S. cerevisiae CCMA 0159 as a biocontrol agent against Aspergillus for application in coffee-producing areas.

Saccharomyces cerevisiae CCMA 0159 showed a high capacity to inhibit OTA-producing Aspergillus species

The use of yeast to biologically control the production of ochratoxin A, which is caused by filamentous fungal growth, in coffee farms is a promising alternative to conventional methods. However, yeast strains, environmental field conditions, and the chemical composition of grains / fruits can influence the effectiveness of biological control agents. We tested the efficiency of different yeast strains in controlling three species of ochratoxigenic fungi in a coffee-based medium. The reasons and mechanisms behind the varying sensitivities of different Aspergillus species to biological control remains unclear. Aspergillus carbonarius rapidly assimilated carbon sources, giving it an advantage over yeasts in substrate colonisation. Saccharomyces cerevisiae CCMA 0159 inhibited all three fungal species, achieving efficiencies of 74.4%, 100%, and 80.9% against A. carbonarius, A. westerdijkiae, and A. ochraceus, respectively. The strategies employed by S. cerevisiae CCMA 0159 to inhibit the growth of ochratoxigenic fungi included competition, production of fungicidal volatile compounds, and alteration of the substrate's physicochemical properties. Our results indicate that among the yeast isolates tested, S. cerevisiae CCMA 0159 is the most effective in inhibiting ochratoxigenic fungi in coffee, including the more resistant A. carbonarius.

Reduction in Ochratoxin A Occurrence in Coffee: From Good Practices to Biocontrol Agents

Ochratoxin A (OTA) is a mycotoxin mainly produced by Aspergillus section Circumdati and section Nigri across the coffee chain. OTA is nephrotoxic and is a threat to human health. This review summarizes current knowledge on how to reduce OTA concentration in coffee from farm to cup. After a brief introduction to the OTA occurrence in coffee, current good management practices are introduced. The core of this review focuses on biocontrol and microbial decontamination by lactic acid bacteria, yeasts and fungi, and their associated enzymes currently reported in the literature. Special attention is given to publications closest to in vivo applications of biocontrol agents and microbial OTA adsorption or degradation agents. Finally, this review provides an opinion on which future techniques to promote within the coffee supply chain.

Changing climate, shifting mycotoxins: A comprehensive review of climate change impact on mycotoxin contamination

Climate change (CC) is a complex phenomenon that has the potential to significantly alter marine, terrestrial, and freshwater ecosystems worldwide. Global warming of 2°C is expected to be exceeded during the 21st century, and the frequency of extreme weather events, including floods, storms, droughts, extreme temperatures, and wildfires, has intensified globally over recent decades, differently affecting areas of the world. How CC may impact multiple food safety hazards is increasingly evident, with mycotoxin contamination in particular gaining in prominence. Research focusing on CC effects on mycotoxin contamination in edible crops has developed considerably throughout the years. Therefore, we conducted a comprehensive literature search to collect available studies in the scientific literature published between 2000 and 2023. The selected papers highlighted how warmer temperatures are enabling the migration, introduction, and mounting abundance of thermophilic and thermotolerant fungal species, including those producing mycotoxins. Certain mycotoxigenic fungal species, such as Aspergillus flavus and Fusarium graminearum, are expected to readily acclimatize to new conditions and could become more aggressive pathogens. Furthermore, abiotic stress factors resulting from CC are expected to weaken the resistance of host crops, rendering them more vulnerable to fungal disease outbreaks. Changed interactions of mycotoxigenic fungi are likewise expected, with the effect of influencing the prevalence and co-occurrence of mycotoxins in the future. Looking ahead, future research should focus on improving predictive modeling, expanding research into different pathosystems, and facilitating the application of effective strategies to mitigate the impact of CC.

Action of the fungal compound citrinin, a bioherbicide candidate, on photosystem II

BACKGROUND

Bioherbicides are becoming more attractive as safe weed control tools towards sustainable agriculture. Natural products constitute an important source chemicals and chemical leads for discovery and development of novel pesticide target sites. Citrinin is a bioactive compound produced by fungi of the genera Penicillium and Aspergillus. However, its physiological-biochemical mechanism as a phytotoxin remains unclear.

RESULTS

Citrinin causes visible leaf lesions on Ageratina adenophora similar to those produced by the commercial herbicide bromoxynil. Phytotoxicity bioassay tests using 24 plant species confirmed that citrinin has a broad activity spectrum and therefore has potential as a bioherbicide. Based on chlorophyll fluorescence studies, citrinin mainly blocks PSII electron flow beyond plastoquinone QA at the acceptor side, resulting in the inactivation of PSII reaction centers. Furthermore, molecular modeling of citrinin docking to the A. adenophora D1 protein suggests that it binds to the plastoquinone QB site by a hydrogen bond between the O1 hydroxy oxygen atom of citrinin and the histidine 215 of the D1 protein, the same way as classical phenolic PSII herbicides do. Finally, 32 new citrinin derivatives were designed and sorted according to free energies on the basis of the molecular model of an interaction between the citrinin molecule and the D1 protein. Five of the modeled compounds had much higher ligand binding affinity within the D1 protein compared with lead compound citrinin.

CONCLUSION

Citrinin is a novel natural PSII inhibitor that has the potential to be developed into a bioherbicide or utilized as a lead compound for discovery of new derivatives with high herbicidal potency. © 2023 Society of Chemical Industry.

Isoenzyme N-Acyl-l-Amino Acid Amidohydrolase NA Increases Ochratoxin A Degradation Efficacy of Stenotrophomonas sp. CW117 by Enhancing Amidohydrolase ADH3 Stability

Ochratoxin A (OTA) is a potent mycotoxin mainly produced by toxicogenic strains of Aspergillus spp. and seriously contaminates foods and feedstuffs. OTA detoxification strategies are significant to food safety. A superefficient enzyme ADH3 to OTA hydrolysis was isolated from the difunctional strain Stenotrophomonas sp. CW117 in our previous study. Here, we identified a gene N-acyl-l-amino acid amidohydrolase NA, which is an isoenzyme of ADH3. However, it is not as efficient a hydrolase as ADH3. The kinetic constant showed that the catalytic efficiency of ADH3 (K_cat/K_m = 30,3938 s^-1 · mM^-1) against OTA was 29,113 times higher than that of NA (K_cat/K_m = 10.4 s^-1 · mM^-1), indicating that ADH3 was the overwhelming superior detoxifying gene in CW117. Intriguingly, when gene na was knocked out from the CW117 genome, degradation activity of the Δna mutant was significantly reduced at the first 6 h, suggesting that the two enzymes might have an interactive effect on OTA transformation. Gene expressions and Western blotting assay showed that the Δna mutant and wild-type CW117 showed similar adh3 expression levels, but na deficiency decreased ADH3 protein level in CW117. Collectively, isoenzyme NA was identified as a factor that improved the stability of ADH3 in CW117 but not as a dominant hydrolase for OTA transformation. IMPORTANCE Ochratoxin A (OTA) is a potent mycotoxin mainly produced by toxicogenic strains of Aspergillus spp. and seriously contaminates foods and feedstuffs. Previous OTA detoxification studies mainly focused on characterizations of degradation strains and detoxifying enzymes. Here, we identified a gene N-acyl-l-amino acid amidohydrolase NA from strain CW117, which is an isoenzyme of the efficient detoxifying enzyme ADH3. Isoenzyme NA was identified as a factor that improved the stability of ADH3 in CW117 and, thus, enhanced the degradation activity of the strain. This is the first study on an isoenzyme improving the stability of another efficient detoxifying enzyme in vivo.

Comprehensive Review of Fungi on Coffee

Coffee is grown in more than 80 countries as a cash crop and consumed worldwide as a beverage and food additive. It is susceptible to fungal infection during growth, processing and storage. Fungal infections, in particular, can seriously affect the quality of coffee and threaten human health. The data for this comprehensive review were collected from the United States Department of Agriculture, Agricultural Research Service (USDA ARS) website and published papers. This review lists the fungal species reported on coffee based on taxonomy, life mode, host, affected plant part and region. Five major fungal diseases and mycotoxin-producing species (post-harvest diseases of coffee) are also discussed. Furthermore, we address why coffee yield and quality are affected by fungi and propose methods to control fungal infections to increase coffee yield and improve quality. Endophytic fungi and their potential as biological control agents of coffee disease are also discussed.

Determination and Comprehensive Risk Assessment of Dietary Exposure to Ochratoxin A on Fermented Teas

A specialized method for ochratoxin A (OTA) determination on fermented teas was developed and validated using ultraperformance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Methodology results showed that recovery, relative standard deviation, accuracy, and precision were qualified. The limits of detection and quantification were 0.32 and 0.96 μg/kg, respectively. Two of 158 collected samples were screened for OTA contamination. Comprehensive risk assessment based on OTA contaminations of this study and other peer-reviewed publications was performed. The highest hazard quotient (HQ) value (8.86 × 10^-2) and the highest 1/MoE value (8.61 × 10^-5) in probabilistic assessment were equally below the recommended non-neoplastic and neoplastic thresholds, indicating no health risks. However, the HQ and 1/MoE values of the 95th percentiles in 20-39 and ≥50 years of age were close to thresholds of 1.0 and 1.0 × 10^-4, respectively. Under the extreme case, there were only a few scenarios (e.g., 40-49 years of age) of HQ values below the non-neoplastic threshold, but the 1/MoE value of each group exceeded the neoplastic threshold. This is the first extensive risk assessment on OTA from fermented teas worldwide, but the sample size is still limited, and a large number of samples is encouraged in a future study for a more accurate assessment.

Predictive Modeling and Validation on Growth, Production of Asexual Spores and Ochratoxin A of Aspergillus Ochraceus Group under Abiotic Climatic Variables

This study aimed to generate predictive models for growth, sporulation, and ochratoxin A (OTA) production under abiotic climatic variables, including temperatures (15-35 °C) and water activity levels (0.99-0.90 aw) by Aspergillus ochraceus group. The data were divided into three sets: one for training, one for testing, and the third one for model validation. Optimum growth occurred at 0.95 aw and 25 °C and 0.95 aw and 30 °C for A. westerdijkiae and A. steynii, respectively. Significantly improved A. westerdijkiae and A. steynii spore production occurred at 0.95 aw and 20 °C and 0.90 aw and 35 °C, respectively. A. steynii and A. westerdijkiae produced the majority of OTA at 35 °C and 0.95 aw and 25-30 °C at 0.95-0.99 aw, respectively. The accuracy of the third-order polynomial regression model reached 96% in growth cases, 94.7% in sporulation cases, and 90.9% in OTA production cases; the regression coefficients (R2) ranged from 0.8819 to 0.9978 for the Aspergillus ochraceus group. A reliable agreement was reached between the predicted and observed growth, sporulation, and OTA production. The effects of abiotic climatic variables on growth, sporulation, and OTA production of A. ochraceus group have been effectively defined, and the models generated were responsible for adequately predicted and validated models against data from other strains within A. ochraceus group that had been published in the literature under the current treatments. These models could be successfully implemented to predict fungal growth and OTA contamination on food matrices for these strains under these conditions.

Ochratoxin A and citrinin in green coffee and dietary supplements with green coffee extract

The aim of this study was to determine the degree of mold contamination and mycotoxin levels in commercially available green coffee products and dietary supplements with green coffee extract. The study included 34 samples from green coffee products: raw beans (n = 16), ground coffee (n = 15) and instant coffee (n = 3), as well as 22 samples from dietary supplements in form of capsules (n = 19), tablets (n = 2) and sachets (n = 1). Total mold count was determined with spread-plate method. Anamorphic mold were identified based on their microscopic morphology and the type of sporulation. Concentrations of mycotoxins, ochratoxin A and citrinin, were quantified by means of HPLC-fluorescence detection. Molds, typically Aspergillus spp. and Penicillium spp., were found in 94% of green coffee beans, 100% of ground and instant coffee samples, and 55% of dietary supplement samples. None of the samples contained detectable levels of citrinin. Ochratoxin A (0.4 ng/g) was detected in only one sample of raw green coffee beans, but in up to 40% and 67% of ground and instant coffee samples, respectively. Mean concentrations of ochratoxin A in ground and instant coffee samples were 3.28 ng/g and 4.09 ng/g, respectively, and maximum concentrations amounted to 6.65 ng/g and 7.44 ng/g, respectively. Ochratoxin A (mean concentration 9.60 ng/g, maximum level 31.4 ng/g) was also detected in up to 58% of the supplement capsules, but in none of tablets and sachets.

Ecophysiology of Penicillium expansum and patulin production in synthetic and olive-based media

Olives and their derivatives, in particular olive oil, represent one of the most significant agricultural products in the Mediterranean basin. Storage under inadequate conditions poses serious problems concerning fungal contamination, with consequent defects and potential mycotoxin production in olives and olive oils. Penicillium expansum represents one of the most significant postharvest pathogens in several fruits, including olives. Not only it causes blue mold but also is one of the most relevant patulin producing species of the genus Penicillium. The aim of this research was to evaluate the ecophysiological conditions governing growth and PAT production by P. expansum strains previously isolated from Tunisian olives. For this purpose, four P. expansum isolates were tested in a synthetic medium (Czapek Yeast Autolysate, CYA) and in olive-based medium (OM) for their ability to grow and produce PAT under different temperatures (4 °C, 15 °C and 25 °C) for 10 and 20 d. The mycotoxin was analysed by HPLC-UV. Results showed that all isolates were able to grow on tested media at different temperatures. Different PAT production profiles were found, showing that at 25 °C P. expansum isolates were able to produce PAT on CYA and OM medium. At 15 °C the production of PAT was only detected on CYA medium, while no PAT production was detected at 4 °C for the two media.

Differentiation and quantification of the ochratoxin A producers Aspergillus ochraceus and Aspergillus westerdijkiae using PCR-DGGE

Ochratoxin A (OTA) is a nephrotoxic, teratogenic, immunotoxic, and carcinogenic mycotoxin which is produced in tropical zones mainly by Aspergillus carbonarius, A. niger, A. ochraceus, and A. westerdijkiae. A. ochraceus and A. westerdijkiae species are phenotypically and genomically very close but A. westerdijkiae produce OTA at a very higher level than A. ochraceus. These species have been differentiated recently. The DNA primer pairs which were drawn so far are not specific and a genomic region of the same size is amplified for both species or they are too specific, and in this case, the DNA of a single species is amplified. To help preventing OTA contamination of foodstuffs, the PCR-DGGE (Denaturing Gradient Gel Electrophoresis) method was used to discriminate between A. ochraceus and A. westerdijkiae DNA fragments of the same size but with different sequences and thus faster access to a diagnosis of the toxigenic potential of the fungal microflora. The proposed methodology was able to differentiate A. westerdijkiae from A. ochraceus with only one primer pairs in a single run. A calibration based on initial DNA content was obtained from image analysis of the DGGE gels and a method of quantification of the two strains was proposed.

Aspergillus Species and Their Associated Mycotoxins

The genus Aspergillus is among the most abundant and widely distributed organism on earth, and at the moment comprises 339 known species. It is one of the most important economically fungal genus and the biotechnological use of Aspergillus species is related to production of soy sauce, of different hydrolytic enzymes (amylases, lipases) and organic acid (citric acid, gluconic acid), as well as biologically active metabolites such as lovastatin. Although they are not considered to be major cause of plant diseases, Aspergillus species are responsible for several disorders in various plants and plant products, especially as opportunistic storage moulds. The notable consequence of their presence is contamination of foods and feeds by mycotoxins, among which the most important are aflatoxins, ochratoxin A, and, at a less extent, fumonisins. Aflatoxins B₁, B₂, G₁, G₂ are the most toxic and carcinogenic mycotoxins, due to their extreme hepatocarcinogenicity; ochratoxin A is a potent nephrotoxin, it is also carcinogenic, teratogenic, and immunotoxic in rats and possibly in humans; fumonisins are hepatotoxic and nephrotoxic with potential carcinogenic effects on rat and mice. In this chapter we summarize the main aspects of morphology, ecology, epidemiology, and toxigenicity of Aspergillus foodborne pathogens which belong to sections Flavi, Circumdati, and Nigri, occurring in several agricultural products and responsible of aflatoxin, ochratoxin A, and fumonisins contamination of food and feed.

Challenges in Specialty Coffee Processing and Quality Assurance

Coffee is an important crop that assures a sustainable economy to farmers in tropical regions. A dramatic concern for coffee production is currently represented by climate change, which threatens the survival of Coffea arabica cultivation worldwide and imposes modifications of the agronomic practices to prevent this risk. The quality of coffee beans depends on optimized protocols of cultivation, ripe berries collection, and removal of the outer fruit layers by dry or wet processes and moisture reduction. Storage and shipment represent two steps where bean quality needs to be preserved by preventing fungal contamination that may impact the final product and form mycotoxins, mainly ochratoxin A. In this review, we describe the challenges faced by the coffee industry to guarantee quality from production to roasting and brewing. An overview of novel technologies, such as the application of starter cultures in fermentation and the exploitation of industrial enzymes in accelerating the process of flavour development in coffee beans, is given. Moreover, the results of studies on microbial populations on coffee and the differences found in fungi, yeasts and bacteria composition among the investigations, are summarized. In particular, this review describes new attempts to contain the development of mycotoxigenic fungi, through the application of antagonistic microorganisms such as S. cerevisiae. The new wave of specialty coffees, i.e., those with a cupping score higher than 85/100, is also presented. It is shown how, through careful coffee production methods and controlled fermentation processes, coffee producers may increase their income by assuring high standards of quality and high added value for the coffee experience sector.

Ochratoxin A Producing Fungi, Biosynthetic Pathway and Regulatory Mechanisms

Ochratoxin A (OTA), mainly produced by Aspergillus and Penicillum species, is one of the most important mycotoxin contaminants in agricultural products. It is detrimental to human health because of its nephrotoxicity, hepatotoxicity, carcinogenicity, teratogenicity, and immunosuppression. OTA structurally consists of adihydrocoumarin moiety linked with l-phenylalanine via an amide bond. OTA biosynthesis has been putatively hypothesized, although several contradictions exist on some processes of the biosynthetic pathway. We discuss recent information on molecular studies of OTA biosynthesis despite insufficient genetic background in detail. Accordingly, genetic regulation has also been explored with regard to the interaction between the regulators and the environmental factors. In this review, we focus on three aspects of OTA: OTA-producing strains, OTA biosynthetic pathway and the regulation mechanisms of OTA production. This can pave the way to assist in protecting food and feed from OTA contamination by understanding OTA biosynthetic pathway and regulatory mechanisms.

Transfer of ochratoxin A into tea and coffee beverages

Ochratoxin A (OTA) is nephrotoxic, hepatotoxic, immunotoxic, neurotoxic, reprotoxic, teratogenic, and carcinogenic (group 2B), being characterized by species and sex differences in sensitivity. Despite the fact that OTA is in some aspects a controversial topic, OTA is the most powerful renal carcinogen. The aim of this study was to make a small survey concerning OTA content in black tea, fruit tea, and ground roasted coffee, and to assess OTA transfer into beverages. OTA content was measured using a validated and accredited HPLC-FLD method with a limit of quantification (LOQ) of 0.35 ng/g. The OTA amount ranged from LOQ up to 250 ng/g in black tea and up to 104 ng/g in fruit tea. Black tea and fruit tea, naturally contaminated, were used to prepare tea infusions. The transfer from black tea to the infusion was 34.8% ± 1.3% and from fruit tea 4.1% ± 0.2%. Ground roasted coffee naturally contaminated at 0.92 ng/g was used to prepare seven kinds of coffee beverages. Depending on the type of process used, OTA transfer into coffee ranged from 22.3% to 66.1%. OTA intakes from fruit and black tea or coffee represent a non-negligible human source.