The inability of Byssochlamys fulva to produce patulin is related to absence of 6-methylsalicylic acid synthase and isoepoxydon dehydrogenase genes

Dissimilarity in sensory attributes, shelf life and spoilage bacterial and fungal microbiota of industrial-scale wet starch noodles induced by different preservatives and temperature

Shelf life, storage stability and microbial growth of wet starch noodles during storage were investigated, and spoilage microbiota was also analyzed to further reveal the decisive factor shaping the microbial community. Sensory analysis and microbiological results indicated that starch noodles treated with sodium dehydroacetate and stored at 4 °C could effectively delay the moldy decay and extend the shelf-life to 50 days, as compared to control and other treatments. In wet starch noodles, molds were found to have a higher spoilage potential than bacteria and yeasts. 16S rDNA sequencing revealed that preservatives, rather than temperature, could cause the significant difference (PERMANOVA p = 0.001) of spoilage bacterial community among samples and sodium dehydroacetate could markedly reduce the bacterial diversity. ITS rDNA sequencing results demonstrated that temperature was the decisive factor in shaping fungal spoilage microbiota (Mantel test r = 0.413, p = 0.002). Besides, Spearman correlation analysis illustrated that the abundance of some microorganisms such as Pseudomonas, Aspergillus and Penicillium were found to be significantly correlated with pH or temperature. These findings provide guiding information in the selection of preservatives and environmental condition for this high-moisture starch noodles.

Volatile 1-octen-3-ol increases patulin production by Penicillium expansum on a patulin-suppressing medium

1-Octen-3-ol is one of the most abundant volatile compounds associated with fungi and functions as a germination and growth inhibitor in several species. By investigating its effect on the biosynthesis of patulin, a mycotoxin made by Penicillium expansum, it was found that a sub-inhibitory level of volatile 1-octen-3-ol increased accumulation of patulin on a medium that normally suppresses the mycotoxin. Transcriptomic sequencing and comparisons of control and treated P. expansum grown on potato dextrose agar (PDA; patulin permissive) or secondary medium agar (SMA; patulin suppressive) revealed that the expression of gox2, a gene encoding a glucose oxidase, was significantly affected, decreasing 10-fold on PDA and increasing 85-fold on SMA. Thirty other genes, mostly involved in transmembrane transport, oxidation-reduction, and carbohydrate metabolism were also differently expressed on the two media. Transcription factors previously found to be involved in regulation of patulin biosynthesis were not significantly affected despite 1-octen-3-ol increasing patulin production on SMA. Further study is needed to determine the relationship between the upregulation of patulin biosynthesis genes and gox2 on SMA, and to identify the molecular mechanism by which 1-octen-3-ol induced this effect.

Evaluation of interleukin-6 concentration in the liver of Albino Swiss mice after intoxication with various doses of patulin

Patulin is a mycotoxin produced by many species of the fungi. The toxic action of patulin mainly affects the gastrointestinal tract and the immune system. The aim of our work was to assess the toxic effect of patulin, based on the analysis of interleukin IL-6 concentrations in the liver of test animals loaded with different doses of this mycotoxin. The research was conducted on mice which were assigned to 6 groups receiving different doses of active substances. After decapitation, their livers were taken for laboratory testing.

Our studies have shown that chronic intoxication with patulin at 0.1 LD50 leads to a statistically significant increase in IL-6 concentration in the liver of the animals. We also found that the loading of experimental animals with a single dose of patulin in the amount of 0.5 LD50 and 0.2 LD50 also leads to a statistically significant increase in this interleukin in the examined organ. There was no difference in its concentration compared to the control group only after the single dose of the lowest concentration of patulin, while the highest average IL-6 concentration was recorded in the liver of animals loaded with the highest single dose of patulin. After applying, one-time doses of this mycotoxin in the amount of 0.2 LD50 and 0.1 LD50, the mean concentrations of IL-6 in the liver in animals from these groups were statistically significantly lower.

In conclusion, the analysis of the obtained results confirms the fact of the hepatotoxic effect of patulin.

Fruit Decay to Diseases: Can Induced Resistance and Priming Help?

Humanity faces the challenge of having to increase food production to feed an exponentially growing world population, while crop diseases reduce yields to levels that we can no longer afford. Besides, a significant amount of waste is produced after fruit harvest. Fruit decay due to diseases at a post-harvest level can claim up to 50% of the total production worldwide. Currently, the most effective means of disease control is the use of pesticides. However, their use post-harvest is extremely limited due to toxicity. The last few decades have witnessed the development of safer methods of disease control post-harvest. They have all been included in programs with the aim of achieving integrated pest (and disease) management (IPM) to reduce pesticide use to a minimum. Unfortunately, these approaches have failed to provide robust solutions. Therefore, it is necessary to develop alternative strategies that would result in effective control. Exploiting the immune capacity of plants has been described as a plausible route to prevent diseases post-harvest. Post-harvest-induced resistance (IR) through the use of safer chemicals from biological origin, biocontrol, and physical means has also been reported. In this review, we summarize the successful activity of these different strategies and explore the mechanisms behind. We further explore the concept of priming, and how its long-lasting and broad-spectrum nature could contribute to fruit resistance.

Comparative Diminution of Patulin Content in Apple Juice With Food-Grade Additives Sodium Bicarbonate, Vinegar, Mixture of Sodium Bicarbonate and Vinegar, Citric Acid, Baking Powder, and Ultraviolet Irradiation

This study aimed to determine an optimal method for patulin (PAT) reduction for application in apple juice production. PAT levels in spiked apple juice (100 μg/L) were measured after treatment with citric acid, sodium bicarbonate, vinegar, mixture of sodium bicarbonate and vinegar, baking powder, and ultraviolet (UV) irradiation. Treatments with sodium bicarbonate and UV irradiation were most effective in reducing PAT; however, UV irradiation reduced the yellowness (b∗) of apple juice. However, sodium bicarbonate treatment affected quality attributes including soluble solids, pH, and color of apple juice. The color and odor of apple juice treated with sodium bicarbonate could be recovered via addition of citric acid. The present results suggest that sodium bicarbonate could be considered an additive in apple juice for PAT reduction.

Apple Intrinsic Factors Modulating the Global Regulator, LaeA, the Patulin Gene Cluster and Patulin Accumulation During Fruit Colonization by Penicillium expansum

The mycotoxin patulin is produced in colonized tissue by Penicillium expansum during storage of apples and is significantly affected by environmental factors that contribute to its accumulation. Few reports have, however, examined the effect of natural intrinsic factors associated with the fruit on the production of patulin. Here, we find that with advancing maturity, Golden Delicious apples show increased concentrations of total soluble solids (TSS) from 14 to 17% associated with the increased expression of the global transcription factor involved in regulation of secondary metabolite biosynthesis in filamentous fungi, laeA expression and patulin accumulation. However, the apple cultivar Granny Smith, with similar TSS values but differing in pH levels and malic acid concentrations, showed reduced expression levels of laeA and the patulin biosynthesis gene cluster (pat genes) and patulin accumulation, suggesting a complexity of host factors contribution to patulin accumulation during P. expansum colonization. To start elucidating these apple intrinsic factors, we examined their in vitro impact on laeA and pat gene expression concomitant with patulin synthesis. Increasing sucrose concentrations from 15 to 175 mM repressed laeA and pat gene expression and patulin production. However, this affect was modified and often reversed and sometimes accentuated by changes in pH, or the addition of malic acid or the major apple phenolic compounds, chlorogenic acid and epicatechin. While the increase in malic acid from 0 to 1% increased laeA and pat gene expression, the decrease in pH from 3.5 to 2.5 reduced their expression. Also the increased laeA and pat genes expressions at increasing epicatechin concentrations from 0 to 1 mM, was reversed by increasing sucrose concentrations, all together suggesting the complexity of the interactions in vivo.

Lichen Biosynthetic Gene Clusters Part II: Homology Mapping Suggests a Functional Diversity

Lichens are renowned for their diverse natural products though little is known of the genetic programming dictating lichen natural product biosynthesis. We sequenced the genome of Cladonia uncialis and profiled its secondary metabolite biosynthetic gene clusters. Through a homology searching approach, we can now propose specific functions for gene products as well as the biosynthetic pathways that are encoded in several of these gene clusters. This analysis revealed that the lichen genome encodes the required enzymes for patulin and betaenones A-C biosynthesis, fungal toxins not known to be produced by lichens. Within several gene clusters, some (but not all) genes are genetically similar to genes devoted to secondary metabolite biosynthesis in Fungi. These lichen clusters also contain accessory tailoring genes without such genetic similarity, suggesting that the encoded tailoring enzymes perform distinct chemical transformations. We hypothesize that C. uncialis gene clusters have evolved by shuffling components of ancestral fungal clusters to create new series of chemical steps, leading to the production of hitherto undiscovered derivatives of fungal secondary metabolites.

A critical review of producers of small lactone mycotoxins: patulin, penicillic acid and moniliformin

A very large number of filamentous fungi has been reported to produce the small lactone mycotoxins patulin, penicillic acid and moniliformin. Among the 167 reported fungal producers of patulin, only production by 29 species could be confirmed. Patulin is produced by 3 Aspergillus species, 3 Paecilomyces species, 22 Penicillium species from 7 sections of Penicillium, and one Xylaria species. Among 101 reported producers of penicillic acid, 48 species could produce this mycotoxin. Penicillic acid is produced by 23 species in section Aspergillus subgenus Circumdati section Circumdati, by Malbranchea aurantiaca and by 24 Penicillium species from 9 sections in Penicillium and one species that does not actually belong to Penicillium (P. megasporum). Among 40 reported producers of moniliformin, five species have been regarded as doubtful producers of this mycotoxin or are now regarded as taxonomic synonyms. Moniliformin is produced by 34 Fusarium species and one Penicillium species. All the accepted producers of patulin, penicillic acid and moniliformin were revised according to the new one fungus – one name nomenclatural system, and the most recently accepted taxonomy of the species.

The response of growth and patulin production of postharvest pathogen Penicillium expansum to exogenous potassium phosphite treatment

In this study, the effects of exogenous potassium phosphite (Phi) on growth and patulin production of postharvest pathogen Penicillium expansum were assessed. The results indicated that P. expansum under 5mmol/L Phi stress presented obvious development retardation, yield reduction of patulin and lower infectivity to apple fruit. Meanwhile, expression analysis of 15 genes related to patulin biosynthesis suggested that Phi mainly affected the early steps of patulin synthetic route at transcriptional level. Furthermore, a global view of proteome and transcriptome alteration of P. expansum spores during 6h of Phi stress was evaluated by iTRAQ (isobaric tags for relative and absolute quantitation) and RNA-seq (RNA sequencing) approaches. A total of 582 differentially expressed proteins (DEPs) and 177 differentially expressed genes (DEGs) were acquired, most of which participated in carbohydrate metabolism, amino acid metabolism, lipid metabolism, genetic information processing and biosynthesis of secondary metabolites. Finally, 39 overlapped candidates were screened out through correlational analysis between iTRAQ and RNA-seq datasets. These findings will afford more precise and directional clues to explore the inhibitory mechanism of Phi on growth and patulin biosynthesis of P. expansum, and be beneficial to develop effective controlling approaches based on Phi.

Secondary Metabolites from Penicillium roqueforti, A Starter for the Production of Gorgonzola Cheese

The presence of mold in food, although necessary for production, can involve the presence of secondary metabolites, which are sometimes toxic. Penicillium roqueforti is a common saprophytic fungus but it is also the essential fungus used in the production of Roquefort cheese and other varieties of blue cheese containing internal mold. The study was conducted on industrial batches of Penicillium roqueforti starters used in the production of the Gorgonzola cheese, with the aim to verify the production of secondary metabolites. Nine Penicillium roqueforti strains were tested. The presence of roquefortine C, PR toxin and mycophenolic acid was tested first in vitro, then on bread-like substrate and lastly in vivo in nine cheese samples produced with the same starters and ready to market. In vitro, only Penicillium out of nine produced roquefortine C, four starters showed mycophenolic acid production, while no significant amounts of PR toxin were detected. In the samples grown on bread-like substrate, Penicillium did not produce secondary metabolites, likewise with each cheese samples tested. To protect consumers' health and safety, the presence of mycotoxins needs to be verified in food which is widely consumed, above all for products protected by the protected denomination of origin (DOP) label (i.e. a certificate guaranteeing the geographic origin of the product), such as Gorgonzola cheese.

Sequencing, physical organization and kinetic expression of the patulin biosynthetic gene cluster from Penicillium expansum

Patulin is a polyketide-derived mycotoxin produced by numerous filamentous fungi. Among them, Penicillium expansum is by far the most problematic species. This fungus is a destructive phytopathogen capable of growing on fruit, provoking the blue mold decay of apples and producing significant amounts of patulin. The biosynthetic pathway of this mycotoxin is chemically well-characterized, but its genetic bases remain largely unknown with only few characterized genes in less economic relevant species. The present study consisted of the identification and positional organization of the patulin gene cluster in P. expansum strain NRRL 35695. Several amplification reactions were performed with degenerative primers that were designed based on sequences from the orthologous genes available in other species. An improved genome Walking approach was used in order to sequence the remaining adjacent genes of the cluster. RACE-PCR was also carried out from mRNAs to determine the start and stop codons of the coding sequences. The patulin gene cluster in P. expansum consists of 15 genes in the following order: patH, patG, patF, patE, patD, patC, patB, patA, patM, patN, patO, patL, patI, patJ, and patK. These genes share 60-70% of identity with orthologous genes grouped differently, within a putative patulin cluster described in a non-producing strain of Aspergillus clavatus. The kinetics of patulin cluster genes expression was studied under patulin-permissive conditions (natural apple-based medium) and patulin-restrictive conditions (Eagle's minimal essential medium), and demonstrated a significant association between gene expression and patulin production. In conclusion, the sequence of the patulin cluster in P. expansum constitutes a key step for a better understanding of the mechanisms leading to patulin production in this fungus. It will allow the role of each gene to be elucidated, and help to define strategies to reduce patulin production in apple-based products.

Culturable endophytes of medicinal plants and the genetic basis for their bioactivity

The bioactive compounds of medicinal plants are products of the plant itself or of endophytes living inside the plant. Endophytes isolated from eight different anticancer plants collected in Yunnan, China, were characterized by diverse 16S and 18S rRNA gene phylogenies. A functional gene-based molecular screening strategy was used to target nonribosomal peptide synthetase (NRPS) and type I polyketide synthase (PKS) genes in endophytes. Bioinformatic analysis of these biosynthetic pathways facilitated inference of the potential bioactivity of endophyte natural products, suggesting that the isolated endophytes are capable of producing a plethora of secondary metabolites. All of the endophyte culture broth extracts demonstrated antiproliferative effects in at least one test assay, either cytotoxic, antibacterial or antifungal. From the perspective of natural product discovery, this study confirms the potential for endophytes from medicinal plants to produce anticancer, antibacterial and antifungal compounds. In addition, PKS and NRPS gene screening is a valuable method for screening isolates of biosynthetic potential.

Study on the role of patulin on pathogenicity and virulence of Penicillium expansum

Although the antibacterial activity and toxicity to humans and animals of the mycotoxin patulin are well known, its role in the postharvest decay of apples by Penicillium expansum has never been investigated. In the present study the gene disruption technique was used to alter the sequence of 6-methyl-salicylic acid synthase, an enzyme involved in the first committed step of patulin biosynthesis. Thirty-nine mutants were obtained, however only two of them (M5 and M21) passed the sub-cultural and molecular confirmation tests. They proved to produce 33-41% less patulin than their wild-type (WT) strain, although no difference in the growth and morphology of the colony was observed. Moreover, the mutants showed a significantly reduced pathogenicity and virulence on artificially inoculated apples. In particular, a 33-34% and 47-54% reduction of disease incidence and severity were recorded for M5 and M21, respectively. As confirmation, when the biomass of the mutants was quantified in vivo by Real-time PCR, a significant difference was recorded as compared to the WT and even between mutants. Moreover, when patulin production potential of mutants was restored by exogenous application of the mycotoxin, their ability to cause the disease was not significantly different from that of WT. Finally, mutants showed an increased susceptibility to the application of the antioxidant quercetin, their pathogenicity and virulence being significantly reduced at only 1/100 of the concentration needed for the WT. Based on these findings, patulin seems to have a role in the development of blue mold decay on apples.

Duplex real-time PCR method with internal amplification control for quantification of verrucosidin producing molds in dry-ripened foods

Verrucosidin, which is a tremorgenic mycotoxin responsible for neurological diseases, has been detected in different dry-ripened foods as consequence of the growth of toxigenic molds. To improve food safety, the presence of verrucosidin producing molds in these kind foods should be quantified. The aim of this study was to design a duplex real-time PCR (qPCR) protocol based on TaqMan methodology with an internal amplification control (IAC). Eleven verrucosidin producing and 11 non producing strains belonging to different species often reported in food products were used. Verrucosidin production was tested by micellar electrokinetic capillary electrophoresis (MECE) and high-pressure liquid chromatography-mass spectrometry (HPLC-MS). A primer pair (VerF1/VerR1) and a TaqMan probe (Verprobe) were designed from the SVr1 probe sequence of a verrucosidin producing Penicillium polonicum. The conserved regions of the β-tubulin gene were used to design primers (TubF1/TubR1) and probe (Tubprobe) of the non-competitive IAC. The functionality of the developed method was demonstrated by the high linear relationship of the standard curves which relating Ct values and DNA template of the tested verrucosidin producers using the verrucosidin and IAC primers. The ability to quantify verrucosidin producers of the developed TaqMan assay in all artificially inoculated food samples was successful, with a minimum detection limit of 1 log cfu per gram of food. This qPCR protocol including an IAC could be very useful to quantify verrucosidin producing molds in dry-ripened foods avoiding false negative results. This method should be proposed to monitor the target molds in HACCP programs to prevent the risk of verrucosidin formation and consequently avoid its presence in the food chain.

Development of real-time PCR methods to quantify patulin-producing molds in food products

Patulin is a mycotoxin produced by different Penicillium and Aspergillus strains isolated from food products. To improve food safety, the presence of patulin-producing molds in foods should be quantified. In the present work, two real-time (RTi) PCR protocols based on SYBR Green and TaqMan were developed. Thirty four patulin producers and 28 non-producers strains belonging to different species usually reported in food products were used. The patulin production was tested by mycellar electrokinetic capillary electrophoresis (MECE) and high-pressure liquid chromatography-mass spectrometry (HPLC-MS). A primer pair F-idhtrb/R-idhtrb and the probe IDHprobe were designed from the isoepoxydon dehydrogenase (idh) gene, involved in patulin biosynthesis. The functionality of the developed method was demonstrated by the high linear relationship of the standard curves constructed with the idh gene copy number and Ct values for the different patulin producers tested. The ability to quantify patulin producers of the developed SYBR Green and TaqMan assays in artificially inoculated food samples was successful, with a minimum threshold of 10 conidia g(-1) per reaction. The developed methods quantified with high efficiency fungal load in foods. These RTi-PCR protocols, are proposed to be used to quantify patulin-producing molds in food products and to prevent patulin from entering the food chain.

Influence of package, type of apple juice and temperature on the production of patulin by Byssochlamys nivea and Byssochlamys fulva

Although the production of patulin in apple fruits is mainly by Penicillium expansum, there is no information on the ability of heat resistant moulds that may survive pasteurization to produce this mycotoxin in juice packages during storage and distribution. In this study, the production of patulin by Byssochlamys spp (Byssochlamys nivea FRR 4421, B. nivea ATCC 24008 and Byssochlamys fulva IOC 4518) in cloudy and clarified apple juices packaged in laminated paperboard packages or in polyethylene terephthalate bottles (PET) and stored at both 21 degrees C and 30 degrees C, was investigated. The three Byssochlamys strains were able to produce patulin in both cloudy and clarified apple juices. Overall, the lower the storage temperature, the lower the patulin levels and mycelium dry weight in the apple juices (p<0.05). The greatest variations in pH and degrees Brix were observed in the juices from which the greatest mycelium dry weights were recovered. The maximum levels of patulin recovered from the juices were ca. 150 microg/kg at 21 degrees C and 220 microg/kg at 30 degrees C. HPLC-UV, HPCL-DAD and mass spectrometry analyses confirmed the ability of B. fulva IOC 4518 to produce patulin. Due to the heat resistance of B. nivea and B. fulva and their ability to produce patulin either in PET bottles or in laminated paperboard packages, the control of contamination and the incidence of these fungi should be a matter of concern for food safety. Control measures taken by juice industries must also focus on controlling the ascospores of heat resistant moulds.

Mutagens manufactured in fungal culture may affect DNA/RNA of producing fungi

Self-produced mutagens in culture by fungi may affect DNA analysis of the same fungi. This has not been considered previously. Many fungi produce numerous mutagenic secondary metabolites (SM) in culture. There is a paradox of growing fungi in media to produce representative DNA which also support mutagenic SM. This is a crucial issue in developing diagnostic and phylogenetic methods, especially for closely-related fungi. For example, idh gene analysis of the patulin metabolic pathway in fungi can be interpreted as producing some false negative and positive results in terms of possession, or nonpossession, of the gene from mutated strains. The most obvious mycotoxins and fungi to consider in this regard are aflatoxins and Aspergillus, as aflatoxins are the most mutagenic natural compounds. Many other fungi and SM are relevant. Conditions to grow fungi have not been selected to inhibit SM production although relevant data exist. In fact, fungi repair damaged nucleic acid (NA) and are capable of removing toxins by employing transporter proteins. These and NA repair mechanisms could be inhibited by secondary metabolites. Mutagenic effects may involve inhibition of DNA stabilizing enzymes. There may be an equivalent situation for bacteria. Researchers need to devise methods to reduce SM for valid protocols. More work on how mutagens affect the NA of producing fungus in vitro is required. The current review assesses the potential seriousness of the situation with selected papers.

Biosynthesis and toxicological effects of patulin

Patulin is a toxic chemical contaminant produced by several species of mold, especially within Aspergillus, Penicillium and Byssochlamys. It is the most common mycotoxin found in apples and apple-derived products such as juice, cider, compotes and other food intended for young children. Exposure to this mycotoxin is associated with immunological, neurological and gastrointestinal outcomes. Assessment of the health risks due to patulin consumption by humans has led many countries to regulate the quantity in food. A full understanding of the molecular genetics of patulin biosynthesis is incomplete, unlike other regulated mycotoxins (aflatoxins, trichothecenes and fumonisins), although the chemical structures of patulin precursors are now known. The biosynthetic pathway consists of approximately 10 steps, as suggested by biochemical studies. Recently, a cluster of 15 genes involved in patulin biosynthesis was reported, containing characterized enzymes, a regulation factor and transporter genes. This review includes information on the current understanding of the mechanisms of patulin toxinogenesis and summarizes its toxicological effects.

Modelling the effect of temperature and water activity on the growth rate and growth/no growth interface of Byssochlamys fulva and Byssochlamys nivea

The purpose of the present study was to apply a modelling approach to define the growth rate and growth/no growth interface of Byssochlamys fulva and Byssochlamys nivea on a synthetic medium as a function of temperature and water activity. Both fungal species were grown on malt extract agar at different temperatures (10, 15, 20, 25, 30, 35, 40 and 45 degrees C) and a(w) levels (0.88, 0.90, 0.92, 0.94, 0.96 and 0.99) for a period of 30 days. Growth responses were evaluated over time in terms of colony diameter changes. Growth data were fitted to the primary model of Baranyi and the resulting growth rates were further modeled as a function of temperature and water activity using the cardinal model with inflection (CMI) (Rosso et al., 1993). A logistic regression quadratic polynomial model was also employed to predict the probability of growth over storage time. Estimated parameters for minimum, maximum and optimum temperatures for growth were 9.1 degrees C, 46.4 degrees C and 32.1 degrees C for B. fulva and 10.5 degrees C, 43.2 degrees C and 32.1 degrees C for B. nivea. The respective values for a(w) were 0.893, 0.993 and 0.985 for B. fulva and 0.892, 0.992 and 0.984 for B. nivea. No growth was observed at 0.88 a(w) regardless of temperature for both species, whereas B. nivea ascospores could not grow at 10 and 45 degrees C irrespective of a(w). Regarding growth boundaries, the degree of agreement between predictions and observations was >98% concordant for both species. The erroneously predicted growth cases were 1.4-4.2% false positive and 2.1-3.5% false negative for B. nivea and B. fulva, respectively. The developed logistic model was validated with two literature data sets as well as with data from independent experiments carried out on fruit juices. Validation results showed that agreement with literature data for growth was 25 out of 36 (69.4%) cases, whereas validation on fruit juice data failed in only 6 cases (5 false positives and 1 false negative) out of 128 cases.

Molecular cloning and functional characterization of two CYP619 cytochrome P450s involved in biosynthesis of patulin in Aspergillus clavatus

Patulin is an acetate-derived tetraketide mycotoxin produced by several fungal species, especially Aspergillus, Penicillium and Byssochlamys species. The health risks due to patulin consumption by humans have led many countries to regulate it in human food. Previous studies have shown the involvement of cytochrome P450 monooxygenases in the hydroxylation of two precursors of patulin, m-cresol and m-hydroxybenzylalcohol. In the present study, two cytochrome P450 genes were identified in the genome sequence of Aspergillus clavatus, a patulin-producing species. Both mRNAs were strongly co-expressed during patulin production. CYP619C2, encoded by the first gene, consists of 529 aa, while the second cytochrome, CYP619C3, consists of 524 aa. The coding sequences were used to perform the heterologous expression of functional enzymes in Saccharomyces cerevisiae. The bioconversion assays showed that CYP619C3 catalysed the hydroxylation of m-cresol to yield m-hydroxybenzyl alcohol. CYP619C2 catalysed the hydroxylation of m-hydroxybenzyl alcohol and m-cresol to gentisyl alcohol and 2,5-dihydroxytoluene (toluquinol), respectively. Except for the last compound, all enzyme products are known precursors of patulin. Taken together, these data strongly suggest the involvement of CYP619C2 and CYP619C3 in the biosynthesis of patulin. CYP619C2 and CYP619C3 are located near to two other genes involved in patulin biosynthesis, namely the 6-methylsalicylic acid synthase (6msas) and isoepoxydon dehydrogenase (idh) genes. The current data associated with an analysis of the sequence of A. clavatus suggest the presence of a cluster of 15 genes involved in patulin biosynthesis.