Potential of patulin production by Penicillium expansum strains on various fruits

Research progress on the application of different preservation methods for controlling fungi and toxins in fruit and vegetable

Fruits and vegetables are susceptible to fungal infections during picking, transportation, storage and processing, which have a high potential to produce toxins. Fungi and toxins can cause acute or chronic poisoning after entering the body. In the field of fruit and vegetable preservation, technologies such as temperature control, modified atmosphere, irradiation, application of natural or chemical preservatives, and edible films are commonly used. In practical applications, according to the types, physiological differences and actual needs of fruits and vegetables, suitable preservation methods can be selected to achieve the effect of preservation and control of fungi and toxins. The starting point of fresh-keeping technology is to delay post-harvest senescence of fruits and vegetables, inhibit the respiratory intensity, and control the reproduction of microorganisms, which is important to control the reproduction of fungi and the production of toxins. From the three directions of physical, chemical and biological means, the article analyses and explores the effects of different external factors on the production of toxins and the effects of different preservation techniques on fungal growth and toxin production in fruits and vegetables, in order to provide new ideas for the preservation of fruits and vegetables and the control of harmful substances in food.

Efficacy and Mechanisms of Action of Essential Oils' Vapours against Blue Mould on Apples Caused by Penicillium expansum

Biofumigation with slow-release diffusers of essential oils (EOs) of basil, oregano, savoury, thyme, lemon, and fennel was assessed for the control of blue mould of apples, caused by Penicillium expansum. In vitro, the ability of the six EOs to inhibit the mycelial growth was evaluated at concentrations of 1.0, 0.5, and 0.1%. EOs of thyme, savoury, and oregano, at all three concentrations, and basil, at 1.0 and 0.5%, were effective in inhibiting the mycelial growth of P. expansum. In vivo, disease incidence and severity were evaluated on 'Opal' apples artificially inoculated with the pathogen and treated at concentrations of 1.0% and 0.5% of EOs. The highest efficacy in reducing blue mould was observed with EOs of lemon and oregano at 1.0% after 60 days of storage at 1 ± 1 °C (incidence of rot, 3 and 1%, respectively) and after a further 14 days of shelf-life at 15 ± 1 °C (15 and 17%). Firmness, titratable acidity, and total soluble solids were evaluated at harvest, after cold storage, and after shelf-life. Throughout the storage period, no evident phytotoxic effects were observed. The EOs used were characterised through GC-MS to analyse their compositions. Moreover, the volatile organic compounds (VOCs) present in the cabinets were characterised during storage using the SPME-GC-MS technique. The antifungal effects of EOs were confirmed both in vitro and in vivo and the possible mechanisms of action were hypothesised. High concentrations of antimicrobial and antioxidant compounds in the EOs explain the efficacy of biofumigation in postharvest disease control. These findings provide new insights for the development of sustainable strategies for the management of postharvest diseases and the reduction of fruit losses during storage.

Ultraviolet Applications to Control Patulin Produced by Penicillium expansum CMP-1 in Apple Products and Study of Further Patulin Degradation Products Formation and Toxicity

Patulin is a mycotoxin whose presence in apple-derived products and fruit juices is legally regulated, being its maximum limits established in the legislation of multiple countries. However, the management of contaminated batches is still an issue for producers. This investigation aims to evaluate ultraviolet light (254 nm, UV-C254nm) irradiation to find solutions that can be applied at different stages of the apple juice production chain. In this regard, 8.8 (UV-1) and 35.1 (UV-2) kJ m−2 treatments inactivated spores of Penicillium expansum CMP-1 on the surface of apples. Although the same treatments applied to wounded apples (either before the infection or after the infection, immediately or when the lesion had appeared) did not show any effect on the growth rate of P. expansum during storage (up to 14 days, at 4 or 25 °C), they reduced patulin content per lesion size in apples treated after the infection had occurred (patulin decreased from 2.24 (control) to 0.65 µg kg−1 cm−2 (UV-2 treated apples)). Additionally, the treatment of juice with patulin with ultraviolet light up to 450.6 kJ m−2 resulted in more than 98 % reduction of patulin. Degradation products of patulin after UV-C254nm treatments were tentatively identified by HPLC–MS, and toxicity and biological activities were assessed in silico, and results indicated that such products did not pose an increased risk when compared to patulin.

Possible Reaction Mechanisms Involved in Degradation of Patulin by Heat-Assisted Cysteine under Highly Acidic Conditions

Patulin (PAT) is one of mycotoxins that usually contaminates apple juice, and it is not easily detoxified by cysteine (CYS) at room temperature due to the highly acidic conditions based on the Michael addition reaction. However, it could be effectively degraded by a heating treatment at 120 °C for 30 min in the presence of cysteine. In our study, a total of eight degradation products (DP A–H) were characterized and identified via liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q-TOF-MS) in a negative ion mode, and their structures and formulas were proposed based on their accurate mass data. The fragmentation patterns of PAT and its degradation products were obtained from the MS/MS analysis. Meanwhile, the possible reaction mechanisms involved in the degradation of PAT were established and explained for the first time. According to the relation between the structure and toxicity of PAT, it could be deduced that the toxic effects of PAT degradation products were potentially much less than those of PAT-self.

More than a Virulence Factor: Patulin Is a Non-Host-Specific Toxin that Inhibits Postharvest Phytopathogens and Requires Efflux for Penicillium Tolerance

Mycotoxin contamination is a leading cause of food spoilage and waste on a global scale. Patulin, a mycotoxin produced by Penicillium spp. during postharvest pome fruit decay, causes acute and chronic effects in humans, withstands pasteurization, and is not eliminated by fermentation. While much is known about the impact of patulin on human health, there are significant knowledge gaps concerning the effect of patulin during postharvest fruit-pathogen interactions. Application of patulin on six apple cultivars reproduced some blue mold symptoms that were cultivar-independent and dose-dependent. Identical symptoms were also observed in pear and mandarin orange. Six Penicillium isolates exposed to exogenous patulin exhibited delayed germination after 24 h, yet all produced viable colonies in 7 days. However, four common postharvest phytopathogenic fungi were completely inhibited by patulin during conidial germination and growth, suggesting the toxin is important for Penicillium to dominate the postharvest niche. Using clorgyline, a broad-spectrum efflux pump inhibitor, we demonstrated that efflux plays a role in Penicillium auto-resistance to patulin during conidial germination. The work presented here contributes new knowledge of patulin auto-resistance, its mode of action, and inhibitory role in fungal-fungal interactions. Our findings provide a solid foundation to develop toxin and decay mitigation approaches.

Occurrence and Characterization of Penicillium Species Isolated from Post-Harvest Apples in Lebanon

The apple is one of the most important fruit tree crops in the Mediterranean region. Lebanon, in particular, is among the top apple producer countries in the Middle East; however, recently, several types of damage, particularly rot symptoms, have been detected on fruits in cold storage. This study aims to identify the causal agents of apple decay in Lebanese post-harvest facilities and characterize a set of 39 representative strains of the toxigenic fungus Penicillium. The results demonstrated that blue mould was the most frequent fungal disease associated with apples showing symptoms of decay after 3–4 months of storage at 0 °C, with an average frequency of 76.5% and 80.6% on cv. Red and cv. Golden Delicious apples, respectively. The morphological identification and phylogenetic analysis of benA gene showed that most Penicillium strains (87.2%) belong to P. expansum species whereas the remaining strains (12.8%) belong to P. solitum. Furthermore, 67.7% of P. expansum strains produced patulin when grown on apple puree for 14 days at 25 °C with values ranging from 10.7 mg kg⁻¹ to 125.9 mg kg⁻¹, whereas all P. solitum did not produce the mycotoxin. This study highlights the presence of Penicillium spp. and their related mycotoxin risk during apple storage and calls for the implementation of proper measures to decrease the risk of mycotoxin contamination of apple fruit products.

Rapid Detection and Quantification of Patulin and Citrinin Contamination in Fruits

Patulin (PAT) and citrinin (CTN) are the most common mycotoxins produced by Penicillium and Aspergillus species and are often associated with fruits and fruit by-products. Hence, simple and reliable methods for monitoring these toxins in foodstuffs are required for regular quality assessment. In this study, we aimed to establish a cost-effective method for detection and quantification of PAT and CTN in pome fruits, such as apples and pears, using high-performance liquid chromatography (HPLC) coupled with spectroscopic detectors without the need for any clean-up steps. The method showed good performance in the analysis of these mycotoxins in apple and pear fruit samples with recovery ranges of 55–97% for PAT and 84–101% for CTN, respectively. The limits of detection (LOD) of PAT and CTN in fruits were 0.006 µg/g and 0.001 µg/g, while their limits of quantification (LOQ) were 0.018 µg/g and 0.003 µg/g, respectively. The present findings indicate that the newly developed HPLC method provides rapid and accurate detection of PAT and CTN in fruits.

New Isolated Metschnikowia pulcherrima Strains from Apples for Postharvest Biocontrol of Penicillium expansum and Patulin Accumulation

Wild yeasts isolated from the surface of apples were screened for antagonistic activity against Penicillium expansum, the main producer of the mycotoxin patulin. Three antagonistic yeasts (Y33, Y29 and Y24) from a total of 90 were found to inhibit P. expansum growth. Identification by ITS region sequence and characterization showed that three selected isolates of yeast should be different strains of Metschnikowia pulcherrima. Several concentrations of the selected yeasts were used to study their in vitro antifungal effectivity against P. expansum on Petri dishes (plates with 63.6 cm² surface) whereas their potential activity on patulin reduction was studied in liquid medium. Finally, the BCA that had the best in vitro antifungal capacity against P. and the best patulin degradation capacity was selected to be assessed directly on apples. All the selected strains demonstrated antifungal activity in vitro but the most efficient was the strain Y29. Isolated strains were able to reduce patulin content in liquid medium, Y29 being the only strain that completely reduced patulin levels within 120 h. The application of Y29 as biocontrol agent on the surface of apples inoculated with P. expansum, inhibited fungal growth and patulin production during storage. Therefore, the results shown that this yeast strain could be used for the reduction of P. expansum and its mycotoxin in apples or apple-based products by adapting the procedure application.

Eco-friendly management of postharvest fungal decays in kiwifruit

Kiwifruit is purchased by consumers worldwide and is increasing in demand. Unfortunately, kiwifruit is susceptible to postharvest decay caused by a variety of fungal pathogens, including Botrytis cinerea, Penicillium expansum, Alternaria alternata, Botryosphaeria dothidea, and Diaporthe spp. Among these pathogens, B. cinerea is the most prevalent and devastating. Infections by these fungal pathogens result in a deterioration in fruit quality and a reduction in marketable yield. Eco-friendly methods to control kiwifruit postharvest decay have been explored as alternatives to the use of synthetic fungicides. In this review, we provide an overview and discuss the virulence and pathogenesis of fungi that are causal agents of kiwifruit decay, especially B. cinerea, including recent molecular and genomic studies. Advances in pre- and postharvest measures for postharvest decay management, including biological control, physical applications, the use of natural compounds and plant hormones, and the use of combined methods, are also reviewed. Eco-friendly control measures are a critical component of an integrated management approach for sustainable production of kiwifruit. The need for further research on the use of microbial consortia for the management of postharvest diseases of kiwifruit is also discussed.

Kiwifruit (Actinidia spp.): A review of chemical diversity and biological activities

Kiwifruit (Actinidia spp.) is a commercially important fruit crop. Various species and cultivars, non-fruit plant parts, and agricultural and processing wastes are underutilized. A broad-scoped review of kiwifruit guides further innovative applications. Different kiwifruit varieties and edible and nonedible parts varied in the composition of dietary nutrients including polyphenols, vitamins, dietary fiber, and functional ingredients, such as starch and protease and bioactive phytochemicals. Kiwifruits exhibit antioxidative, antiproliferative, antiinflammatory, antimicrobial, antihypertensive, antihypercholesterolemic, neuroprotective, antiobese properties and promote gut health. Clinically significant effects of kiwifruit on prevention and/or treatment of major chronic diseases are not yet evident. Varieties and plant parts, extraction, analytical and processing methods affect the physicochemical and biological properties of kiwifruit-derived ingredients. Allergens, mycotoxins, pesticides and heavy metals are the chemical hazards of kiwifruits. Future research should be focused on sustainable uses of underutilized resources as functional ingredients, bioactive compound purification, composition-activity relationships, and physiological mechanisms and clinical significance of kiwifruits.

Effect of quorum sensing and quenching molecules on inter-kingdom biofilm formation by Penicillium expansum and bacteria

The ecology of a biofilm is a complex function of different factors, including the presence of microbial metabolites excreted by the inhabitants of the biofilm. This study aimed to assess the effect of patulin, and N-(3-oxododecanoyl)-L-homoserine lactone (3-oxo-C₁₂-HSL) on inter-kingdom biofilm formation between a filamentous fungus and bacteria isolated from drinking water. The filamentous fungus Penicillium expansum and the bacteria Acinetobacter calcoaceticus and Methylobacterium oryzae were used as model species. M. oryzae biofilm formation and development was more susceptible to the presence of the quenching molecules than A. calcoaceticus biofilms. Patulin reduced M. oryzae biofilm growth while 3-oxo-C₁₂-HSL caused an increase after 48 h. The presence of P. expansum had a detrimental effect on M. oryzae cell numbers, while an advantageous effect was observed with A. calcoaceticus. The overall results reveal that quorum sensing and quenching molecules have a significant effect on inter-kingdom biofilm formation, especially on bacterial numbers.

Elaborated regulation of griseofulvin biosynthesis in Penicillium griseofulvum and its role on conidiation and virulence

Penicilium griseofulvum, the causal agent of apple blue mold, is able to produce in vitro and on apple a broad spectrum of secondary metabolites (SM), including patulin, roquefortine C and griseofulvin. Among them, griseofulvin is known for its antifungal and antiproliferative activity, and has received interest in many sectors, from medicine to agriculture. The biosynthesis of SM is finely regulated by filamentous fungi and can involve global regulators and pathway specific regulators, which are usually encoded by genes present in the same gene cluster as the backbone gene and tailoring enzymes. In the griseofulvin gene cluster, two putative transcription factors were previously identified, encoded by genes gsfR1 and gsfR2, and their role has been investigated in the present work. Analysis of P. griseofulvum knockout mutants lacking either gene suggest that gsfR2 forms part of a different pathway and gsfR1 exhibits many spectra of action, acting as regulator of griseofulvin and patulin biosynthesis and influencing conidia production and virulence on apple. The analysis of gsfR1 promoter revealed that the regulation of griseofulvin biosynthesis is also controlled by global regulators in response to many environmental stimuli, such as carbon and nitrogen. The influence of carbon and nitrogen on griseofulvin production was further investigated and verified, revealing a complex network of response and confirming the central role of gsfR1 in many processes in P. griseofulvum.

Effective Adsorption of Patulin from Apple Juice by Using Non-Cytotoxic Heat-Inactivated Cells and Spores of Alicyclobacillus Strains

Patulin (PAT) is a major threat to many food products, especially apple and apple products, causing human health risks and economic losses. The aim of this study was to remove PAT from apple juice by using the heat-inactivated (HI) cells and spores of seven Alicyclobacillus strains under controlled conditions. The HI cells and spores of seven strains adsorbed PAT effectively, and the HI cells and spores of Alicyclobacillus acidocaldarius DSM 451 (A51) showed maximum PAT adsorption capacity of up to 12.621 μg/g by HI cells and 11.751 μg/g by HI spores at 30 °C and pH 4.0 for 24 h. Moreover, the PAT adsorption process followed the pseudo-first order kinetic model and the Freundlich isotherm model; thermodynamic parameters revealed that PAT adsorption is a spontaneous exothermic physisorption process. The results also indicated that PAT adsorption is strain-specific. The HI cells and spores of Alicyclobacillus strains are non-cytotoxic, and the bioadsorption of PAT did not affect the quality of the juice. Furthermore, the cell wall surface plays an important role in the adsorption process.

Penicillium Species and Their Associated Mycotoxins

Penicillium are very diverse and cosmopolite fungi, about 350 species are recognized within this genus. It is subdivided in four subgenera Aspergilloides, Penicillium, Furcatum, and Biverticillium; recently the first three has been included in Penicillium genus, and Biverticillium under Talaromyces. They occur worldwide and play important roles as decomposers of organic materials, cause destructive rots in the food industry where produces a wide range of mycotoxins; they are considered enzyme factories, and common indoor air irritants. In terms of human health are rarely associated as human pathogen because they hardly growth at 37°, while the main risk is related to ingestion of food contaminated by mycotoxins produced by several species of Penicillium. Various mycotoxins can occur in foods and feeds contaminated by Penicillium species, the most important are ochratoxin A and patulin; for which regulation are imposed in a number of countries, and at a less extent cyclopiazonic acid. In this chapter we summarize the main aspect of the morphology, ecology and toxigenicity of Penicillium foodborne mycotoxigenic species which belong mainly in subgenus Penicillium sections Brevicompacta, Chrysogena, Fasciculata, Penicillium, and Roquefortorum.

Patulin adsorption of a superior microorganism strain with low flavour-affection of kiwi fruit juice

The aim of this study was to isolate a microbial strain with higher patulin adsorption capability and lower flavour-affection on kiwi fruit juice, and study patulin adsorption behaviour effects on cell morphology and adsorption kinetics. Electronic-nose and physicochemical analysis methods were combined to evaluate the flavour and quality of treated kiwi fruit juice. The results showed that yeasts had a good performance on biomass, patulin adsorption and flavour maintenance. Besides, patulin adsorption behaviour and kinetic study of yeast strain N-10 was investigated, the results showed that patulin adsorption capability was influenced by cell morphology, its adsorption behaviour followed pseudo-first-order reaction kinetics, and equilibrium experiments fit the Langmuir isotherm model. The investigation revealed that patulin adsorption is a spontaneous endothermic physic-sorption behaviour. During adsorption, patulin moved from the liquid to the adsorbent surface and the capability of adsorbents was associated with their cell surface morphology. This study provides a basis for the selection of strains with improved patulin adsorption from kiwi fruit juice and provides the experimental foundation and theoretical basis for future studies of patulin adsorption in fruit juice, it has great potential application for the control of patulin in the juice processing industry.

Effect of Yeast Cell Morphology, Cell Wall Physical Structure and Chemical Composition on Patulin Adsorption

The capability of yeast to adsorb patulin in fruit juice can aid in substantially reducing the patulin toxic effect on human health. This study aimed to investigate the capability of yeast cell morphology and cell wall internal structure and composition to adsorb patulin. To compare different yeast cell morphologies, cell wall internal structure and composition, scanning electron microscope, transmission electron microscope and ion chromatography were used. The results indicated that patulin adsorption capability of yeast was influenced by cell surface areas, volume, and cell wall thickness, as well as 1,3-β-glucan content. Among these factors, cell wall thickness and 1,3-β-glucan content serve significant functions. The investigation revealed that patulin adsorption capability was mainly affected by the three-dimensional network structure of the cell wall composed of 1,3-β-glucan. Finally, patulin adsorption in commercial kiwi fruit juice was investigated, and the results indicated that yeast cells could adsorb patulin from commercial kiwi fruit juice efficiently. This study can potentially simulate in vitro cell walls to enhance patulin adsorption capability and successfully apply to fruit juice industry.

Accumulation of the mycotoxin patulin in the presence of gluconic acid contributes to pathogenicity of Penicillium expansum

Penicillium expansum, the causal agent of blue mold rot, causes severe postharvest fruit maceration through secretion of D-gluconic acid (GLA) and secondary metabolites such as the mycotoxin patulin in colonized tissue. GLA involvement in pathogenicity has been suggested but the mechanism of patulin accumulation and its contribution to P. expansum pathogenicity remain unclear. The roles of GLA and patulin accumulation in P. expansum pathogenicity were studied using i) glucose oxidase GOX2-RNAi mutants exhibiting decreased GOX2 expression, GLA accumulation, and reduced pathogenicity; ii) IDH-RNAi mutants exhibiting downregulation of IDH (the last gene in patulin biosynthesis), reduced patulin accumulation, and no effect on GLA level; and iii) PACC-RNAi mutants exhibiting downregulation of both GOX2 and IDH that reduced GLA and patulin production. Present results indicate that conditions enhancing the decrease in GLA accumulation by GOX2-RNAi and PACC-RNAi mutants, and not low pH, affected patulin accumulation, suggesting GLA production as the driving force for further patulin accumulation. Thus, it is suggested that GLA accumulation may modulate patulin synthesis as a direct precursor under dynamic pH conditions modulating the activation of the transcription factor PACC and the consequent pathogenicity factors, which contribute to host-tissue colonization by P. expansum.

Adsorptive removal of patulin from apple juice using Ca-alginate-activated carbon beads

This study aimed to investigate the adsorption of patulin from apple juice by Ca-alginate-activated carbon (Ca-alginate-AC) beads. The capacity of patulin was determined by high-performance liquid chromatography. The results showed that Ca-alginate-AC beads have significant ability to reduce patulin from contaminated apple juice. Furthermore, the adsorption process did not affect the quality of apple juice. The effects of contact time, initial patulin concentration, adsorbent dose, and temperature were assessed. The removal percentage of patulin increased with contact time, adsorbent dose, and temperature. A reduction was also noted to bind patulin at increased levels of contamination. The equilibrium data were fitted to Langmuir, Freundlich, and Temkin isotherm models and the isotherm constants were calculated at different temperatures. The adsorption equilibrium was best described by the Freundlich isotherm (R(2) > 0.990). The pseudo 1st-order model was found to describe the kinetic data satisfactorily. Thermodynamic parameters such as standard Gibbs free energy (ΔG◦◦), standard enthalpy (ΔH◦), and standard entropy (ΔS◦) were evaluated. The results showed that the adsorption was spontaneous and endothermic nature.

Genetic structure and natural variation associated with host of origin in Penicillium expansum strains causing blue mould

Blue mould, caused by Penicillium expansum, is one of the most economically damaging postharvest diseases of pome fruits, although it may affect a wider host range, including sweet cherries and table grapes. Several reports on the role of mycotoxins in plant pathogenesis have been published, but few focussed on the influence of mycotoxins on the variation in host preference amongst producing fungi. In the present study the influence of the host on P. expansum pathogenicity/virulence was investigated, focussing mainly on the relationship with patulin production. Three P. expansum strain groups, originating from apples, sweet cherries, and table grapes (7 strains per host) were grown on their hosts of isolation and on artificial media derived from them. Strains within each P. expansum group proved to be more aggressive and produced more patulin than the other two groups under evaluation when grown on the host from which they originated. Table grape strains were the most aggressive (81% disease incidence) and strongest patulin producers (up to 554μg/g). The difference in aggressiveness amongst strains was appreciable only in the presence of a living host, suggesting that the complex pathogen-host interaction significantly influenced the ability of P. expansum to cause the disease. Incidence/severity of the disease and patulin production proved to be positively correlated, supporting the role of patulin as virulence/pathogenicity factor. The existence of genetic variation amongst isolates was confirmed by the High Resolution Melting method that was set up herein, which permitted discrimination of P. expansum from other species (P. chrysogenum and P. crustosum) and, within the same species, amongst the host of origin. Host effect on toxin production appeared to be exerted at a transcriptional level.