Expansum Growth Research Articles

The Biophysical Properties of the Fruit Cuticles of Six Pear Cultivars during Postharvest Ripening

Pears are abundant in bioactive compounds, which exert favorable effects on human health. The biophysical attributes of fruit cuticles are pivotal in determining fruit quality, storability, and susceptibility to mold growth. This study aimed to elucidate the biophysical properties of six pear cultivars, ‘Conference’, ‘Celina’, ‘Abate Fetel’, ‘Packham’s Triumph’, ‘Sweet Sensation’, and ‘Williams’. Two maturity stages, unripe and fully ripened, were investigated. Furthermore, the efficacy of trimethyl-chitosan-coated pear surfaces in preventing Penicillium expansum (P. expansum) growth was assessed. Basic maturity indices (CIE color, ethylene evolution, firmness, soluble solids), cuticle contact angle, roughness, and zeta potential were analyzed. Surface roughness was measured using an optical profilometer, hydrophobicity was measured via profilometry, and zeta potential was quantified using an electrokinetic analyzer. The ‘Celina’ cultivar exhibited the highest roughness, whereas ‘Williams’ had the lowest roughness. All the cultivars’ cuticles demonstrated hydrophilic characteristics, with contact angles ranging between 65° and 90°. For pH values exceeding 3.5, all pear surfaces exhibited a negative zeta potential. P. expansum growth was the slowest on the ‘Packham’s Triumph’ and ‘Conference’ cultivars. Treatment with trimethyl chitosan effectively inhibited P. expansum growth in the initial hours of incubation. In conclusion, diverse pear cultivars manifest distinct biophysical surface properties and varying susceptibility to P. expansum growth. The growth of P. expansum correlates positively with roughness, contact angle, and zeta potential. These differences can significantly impact shelf life potential and the overall postharvest quality of pears.

A glycoside hydrolase superfamily gene plays a major role in Penicillium expansum growth and pathogenicity in apples

Penicillium expansum is an important postharvest pome fruit pathogen causing massive spoilage of stored fruits and high economic losses. The present study aimed to identify an essential gene of P. expansum and to investigate its effect in postharvest apple infection. Cytoscape and RNA-sequencing analysis identified a P. expansum PeBgl1 gene which was a hub gene and also upregulated expression at three key time points (1, 3, and 6 h) during apple infection. The PeBgl1 gene was 798 bp in length, encoded 265 amino acids and had high homology with glycoside hydrolase superfamily of P. expansum. The PeBgl1 gene affected the colony morphology especially the colony color and delayed fungal growth both of P. expansum both in vivo and in vitro. This gene also decreased the pathogenicity of P. expansum in apples. Based on these results, we conclude that PeBgl1 is responsible for growth and pathogenicity in P. expansum.

Inhibitory effect and mechanism of curcumin-based photodynamic inactivation on patulin secretion by Penicillium expansum

Patulin (PAT) contamination caused by Penicillium expansum growth in postharvest fruit brings safety problems. This study investigated the inhibitory effect and mechanism of curcumin (CUR)-based photodynamic inactivation (PDI) on PAT secreted by P. expansum in vitro using a multifunctional light source instrument. After being treated with photosensitive CUR, the growth of mycelium was completely inhibited on potato dextrose agar medium, and the maximum PAT reduction of 93.06% can be achieved (330.0 J/cm2, 300 μM CUR) in liquid medium. The inherent mechanism was that PDI causes the reactive oxygen species accumulation in cells, which destroyed the antioxidant defense system and induced severe oxidative damage, resulting in the loss of cell integrity. Furthermore, mycelial apoptosis caused up-regulation of five genes, including PatB, PatE, PatG, PatI, and PatL, but down-regulated ten genes in the PAT biosynthetic pathway. These findings suggest that CUR-based PDI can inhibit fungal infection and toxin secretion. Industrial relevanceThis study found that photosensitized curcumin can significantly inhibit mycelial growth and the secretion of patulin by Penicillium expansum. Curcumin-based photodynamic inactivation has the feasibility of the application on fresh fruits and vegetables, such as apples or oranges, and can avoided excessive waste of resources in picking, transporting, storing, and selling.

The necrosis-inducing protein (NIP) gene contributes to Penicillium expansum virulence during postharvest pear infection

Penicillium expansum is the causative fungus of blue mold decay in postharvest pears resulting in substantial economic losses. Investigating P. expansum-pear fruit interactions is necessary to help develop P. expansum control strategies for effective and safe pear production. Investigating the P. expansum gene expression alterations and essential gene functions during the infection process is indispensable. Based on our results, the necrosis-inducing protein (NIP) gene was closely associated with genes related to plant cell wall degrading enzymes (CWDEs) and involved in P. expansum virulence. The NIP has high homology with other already-known fungal NIPs. To evidence the role of NIP in P. expansum virulence, NIP mutant (including knockout (ΔNIP) and complementation mutant (cNIP)) P. expansum were generated. Despite the NIP deletion did not affect the basic morphology and structure of P. expansum, it slowed down the fungal growth and hyphal production, thus reducing P. expansum's sporulation and patulin (PAT) accumulation. Furthermore, the deletion of NIP reduced the pathogenicity of P. expansum in pear. The complementation of NIP (cNIP) restored the growth, conidia production, PAT accumulation, and virulence of ΔNIP to the level of wild-type P. expansum. In addition, PAT can cause decay and aggravate the disease severity of wild-type P. expansum and ΔNIP on pears. Our results confirmed NIP plays a crucial role in P. expansum's growth, hyphal production, and pathogenicity in pears.

Apple-based coatings incorporated with wild apple isolated yeast to reduce Penicillium expansum postharvest decay of apples

The aim of this work has been to prevent the growth of Penicillium expansum on the surface of apples by means of the use of biocontrol agents in combination with edible coatings. For that, Metschnikowia pulcherrima yeast isolated from wild apples was incorporated in edible film matrices based on pectins, cellulose ethers with and without the addition of liquid culture medium (yeast extract and glucose) and apple pomace residues.The viability and biocontrol activity of the yeast incorporated in the films were evaluated after film drying process and after being stored for 21 days at 10 °C. Furthermore, the matrix that exhibited the best results was applied as a coating on apples artificially inoculated with P. expansum in order to evaluate its antifungal activity against P. expansum during storage and to prevent the production of its mycotoxin, the patulin. M. pulcherrima remained viable in films after drying step and after 21 days storage, but viability depended on the matrix composition, being lower in pectin films and higher in apple pomace films. The highest antimicrobial activity in vitro was observed in methylcellulose films supplemented with yeast extract and glucose (YEG), and in apple pomace residues films, matrix which was therefore selected to be applied as coatings on apples inoculated with P. expansum. The results proved that bioactive coatings significantly reduce P. expansum growth and patulin production during storage. The results obtained in this work give added value to the apple industry residues which, in combination with apple isolated M. pulcherrima can be applied as coatings on apples to provide protection against blue mold and its mycotoxin as an alternative of postharvest disease management.

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.

Cinnamon Oil Inhibits Penicillium expansum Growth by Disturbing the Carbohydrate Metabolic Process.

Penicillium expansum is a major postharvest pathogen that mainly threatens the global pome fruit industry and causes great economic losses annually. In the present study, the antifungal effects and potential mechanism of cinnamon oil against P. expansum were investigated. Results indicated that 0.25 mg L−1 cinnamon oil could efficiently inhibit the spore germination, conidial production, mycelial accumulation, and expansion of P. expansum. In addition, it could effectively control blue mold rots induced by P. expansum in apples. Cinnamon oil could also reduce the expression of genes involved in patulin biosynthesis. Through a proteomic quantitative analysis, a total of 146 differentially expressed proteins (DEPs) involved in the carbohydrate metabolic process, most of which were down-regulated, were noticed for their large number and functional significance. Meanwhile, the expressions of 14 candidate genes corresponding to DEPs and the activities of six key regulatory enzymes (involving in cellulose hydrolyzation, Krebs circle, glycolysis, and pentose phosphate pathway) showed a similar trend in protein levels. In addition, extracellular carbohydrate consumption, intracellular carbohydrate accumulation, and ATP production of P. expansum under cinnamon oil stress were significantly decreased. Basing on the correlated and mutually authenticated results, we speculated that disturbing the fungal carbohydrate metabolic process would be partly responsible for the inhibitory effects of cinnamon oil on P. expansum growth. The findings would provide new insights into the antimicrobial mode of cinnamon oil.

Efficacy of methyl thujate in inhibiting Penicillium expansum growth and possible mechanism involved

Abstract Fungal infection causes severe diseases on fruits and vegetables, eventually leading to postharvest loss, and thus it is urgent to explore safe substances to control postharvest diseases and elucidate the underlying antimicrobial mechanisms. Here, it was found that a monoterpenoid substance, methyl thujate, was effective in inhibiting mycelial growth of Penicillium expansum and reducing its virulence on harvested fruit dose-dependently. Moreover, dual-fluorescence staining and flow cytometry assay suggested that methyl thujate significantly decreased cell vitality, impaired membrane integrity, induced ROS accumulation and abolished mitochondrial membrane potential in P. expansum. As a consequence, membrane peroxidation and cytoplasmic content leakages occurred. In summary, methyl thujate could inhibit mycelial growth of P. expansum and reduce its virulence on harvested fruit, which is promising for controlling postharvest decay.

A natural strategy to improve the shelf life of the loaf bread against toxigenic fungi: The employment of fermented whey powder

Whey powders are used as food ingredients in many applications, from bakery goods, soups and sauces to baby food. The objective of the study was to evaluate the antifungal property of a whey‐based medium (WM) fermented by lactic acid bacteria. The antifungal activity of the WM was evaluated using antifungal tests on solid and liquid media. MIC and MFC ranged from 15.6 to 250 mg/mL and 62.5 to 250 mg/mL, respectively. Using fermented WM for dough preparation produced a reduction of Penicillium expansum growth of 0.5–0.6 log CFU/g and an improvement in shelf life of 1–2 days in relation to control bread.

Spatial distribution of flavor components and antioxidants in the flesh of ‘Conference’ pears and its relationship with postharvest pathogens susceptibility

The spatial distribution of dry matter, ethylene production, respiration rate, organic acids, sugars, antioxidants, volatiles and fungal (Penicillium expansum and Rhizopus stolonifer) growth was evaluated analyzing four different slices of ‘Conference’ pear flesh taken along an equatorial radius. A common spatial distribution trend was found for ethylene emission, CO2 production, antioxidant capacity and total phenolic compounds with a minimum in the slice under the skin and a maximum in the slice near the core. Fructose, which was the dominant sugar followed by sucrose and glucose, showed a quasi-linear decreasing profile from the outer slice towards the core. Malic and ascorbic acid had the highest content in the outer slice while citric remained practically constant over the different slices. Twenty-nine volatile organic compounds (VOCs) were identified using solid-phase microextraction (SPME), yet only six of them showed significant differences between flesh slices. The content in VOCs was further related to the tissue susceptibility to the above-mentioned postharvest pathogens using a multivariate approach. Fruit flesh from inner sections was more prone to P. expansum whereas flesh from the slice under the skin presented the highest incidence of R. stolonifer. A Partial Least Square (PLS) model showed that P. expansum growth was negatively correlated with malic acid, dry matter content, 2-ethyl-hexanal and butyl hexanoate concentrations and R. stolonifer was negatively correlated to sucrose and some volatiles such as hexanal and 1-butanol. Based on the results from the PLS, selected volatiles naturally present in the pear flesh were tested in vitro, at different concentrations, in order to investigate their effectiveness to control blue mold caused by P. expansum and soft rot caused by R. stolonifer. A completely control of P. expansum was found with 2-ethyl-hexanal application and hexanal while 1-butanol showed a total fungicide effect against R. stolonifer. This study is a step towards a better understanding of how biochemical compounds are spatially distributed among different slices of ‘Conference’ pears as well as in the development of natural compounds to fight major postharvest pathogens in pear fruit.

Double-bottom antimicrobial packaging for apple shelf-life extension

A package was created that extends apple shelf-life by slowing Penicillium expansum growth. The package consisted of a peelable lid and a tray with a double bottom with inclusion complexes (ICs) of ß-cyclodextrin (ß-CD) containing the essential oils of palmarosa (ICp) or of star anise (ICsa). Oil amounts required for antimicrobial activity were obtained from in vitro assays. After 12 days at 23 °C, P. expansum-inoculated apples in both of the double-bottom antimicrobial packages (DBAP) had 1/3 less fungal growth, less than 50% weight loss and ethylene and CO2 production, and less than 25% firmness loss, TA and SSC increase, and pH decrease compared to controls. The DBAP with ICsa performed better than with ICp in reducing ethylene production, respiration rate, firmness loss, TA increase, and pH decrease. This demonstrates DBAP containing ICp or ICsa can maximize the shelf-life of apples injured by P. expansum, validating a novel type of antimicrobial packaging.

Meyve Sularında Patulin Kirlenmesi ve Kontrol Önlemleri

Patulin is a mycotoxin produced by some Penicillium, Aspergillus, and Byssochlamys mold species . It has been found to impose many adverse health effects, and frequently detection in commercial fruit juices and apple products makes it a public health concern. The most important organism responsible for the patulin contamination in apple and derived products is Penicillium expansum ( P . expansum ) . There have been many studies on inhibition of P . expansum growth in apples/fruits and reduction of patulin contamination in fruit products, however, it still remains as a major contamination problem in these products all around the world. Patulin contamination in apple and other fruit derived products could be prevented by the use of various physical, chemical, and biological control methods. The preventive measures such as Good Pre-harvest and Post-harvest Practices in combination with processing hurdles could be the best solution to avoid the contamination. Research and development to improve the current technologies, understanding and optimization the novel technologies also could serve the best to eliminate the problem.

Inhibitory effect of chlorine dioxide (ClO2) fumigation on growth and patulin production and its mechanism in Penicillum expansum

The effect of chlorine dioxide (ClO2) on Penicillium expansum growth and patulin production in vitro and on its disease severity in apples was investigated. ClO2 treatment significantly reduced the lesion diameter in apples infected with P. expansum and inhibited mycelial growth and spore germination. After ClO2 treatment, P. expansum mycelial morphology was strongly affected, and a reduced spore plasma membrane integrity with an increased malondialdehyde (MDA) mycelial content was observed. Moreover, patulin production by P. expansum was reduced by ClO2 treatment, both in apples and in PDB meidium. These data showed new and precise clues to the inhibitory effect of ClO2 on P. expansum growth, and provided an effective method to ensure safety of apple products caused by P. expansum.

Bamboo leaf flavonoid enhances the control effect of Pichia caribbica against Penicillium expansum growth and patulin accumulation in apples

Patulin (PAT) mainly produced by Penicillium expansum is a very problematic mycotoxin, and its presence is often reported in different foods and food products. The prevention of these products from initial contamination and/or degradation is therefore of foremost importance in protecting consumer health. In this report, Pichia caribbica (1 × 108 cells mL−1) antagonistic yeasts incorporated with bamboo leaf flavonoid (0.01% w/v) were assessed for PAT degradation capabilities in in-vitro and in-vivo. Also the effects of treatments on wound lesion diameter, lignification and pH level were investigated. Clearly, the combined biocontrol agent (P. caribbica and bamboo leaf flavonoid) had the ability to degrade PAT in vitro with undetected level at 96 h of incubation in NYDB media. In apple fruits, PAT accumulation was significantly lower at 20 d (at 20 °C) of storage. Wound lignification was significantly enhanced from 0.31 to 0.27 after 15 d of storage, whereas pH was modified (>4.0) in host; which might lead to an increase in PAT breakdown. P. caribbica combined with bamboo leaf flavonoid could be a promising biocontrol agent for PAT degradation processes in apple fruits.

Patulin production byPenicillium expansum isolates from apples during different steps of long-term storage

Penicillium expansum is the principal cause of blue mould rot and associated production of patulin, a weak mycotoxin, in apples worldwide.P. expansum growth and patulin production is observed during improper or long-term storage of apples. We have investigated the extent to which each successive step during long-term storage contributes to patulin production in variousP. expansum isolates. Fungal isolates collected on apples from several Belgian orchards/industries were identified to species level. Random amplification of polymorphic DNA (RAPD) analysis and β-tubulin gene sequencing identifiedP. expansum andPenicillium solitum as the most prevalentPenicillium species associated with Belgian apples. All 27P. expansum isolates and eight reference strains were characterised for their patulin production capacity on apple puree agar medium for five days under classical constant temperature and atmosphere conditions. Under these conditions, a large range of patulin production levels was observed. Based on this phenotypic diversity, fiveP. expansum isolates and one reference strain were selected forin vitro investigation of patulin production under representative conditions in each step of long-term apple storage. Patulin accumulation seemed highly strain dependent and no significant differences between the storage steps were observed. The results also indicated that a high spore inoculum may lead to a strong patulin accumulation even at cold temperatures (1 °C) combined with controlled atmosphere (CA) (3% O2, 1% CO2), suggesting that future control strategies may benefit from considering the duration of storage under CA conditions as well as duration of deck storage.

In vitro antifungal activity of lactic acid bacteria against mycotoxigenic fungi and their application in loaf bread shelf life improvement

Food spoilage caused by mycotoxigenic fungi represents an important food safety problem. Lactic acid bacteria (LAB) are used as starter cultures in a larger number of food products. In this study, 16 strains of LAB were cultivated in MRS broth under anaerobiosis. Then, cell free supernatants were obtained by centrifugation and their antifungal activity against Aspergillus parasiticus and Penicillium expansum was tested using the disc-diffusion method. Furthermore, the LABs that showed in vitro antifungal activity were used in bread fermentation with yeast in order to study fungal growth inhibition and aflatoxin (AF) reduction in processed bread previously inoculated with A. parasiticus. The compounds present in the fermented medium of six LAB strains induced inhibition of P. expansum growth, whereas five probiotic strains produced antifungal compounds against A. parasiticus. The analysis by liquid chromatography coupled to mass spectrometry in tandem showed a reduction of the AF content in bread samples fermented with yeast and LABs. The reduction of AFs ranged from 84.1 to 99.9%. Moreover, bread sample studies showed a shelf life increase of about 3–4 days.

Isoepoxydon dehydrogenase (idh) gene expression in relation to patulin production by Penicillium expansum under different temperature and atmosphere

Penicillium expansum growth and patulin production occur mainly at post-harvest stage during the long-term storage of apples. Low temperature in combination with reduced oxygen concentrations is commonly applied as a control strategy to extend apple shelf life and supply the market throughout the year. Our in vitro study investigated the effect of temperature and atmosphere on expression of the idh gene in relation to the patulin production by P. expansum. The idh gene encodes the isoepoxydon dehydrogenase enzyme, a key enzyme in the patulin biosynthesis pathway. First, a reverse transcription real-time PCR (RT-qPCR) method was optimized to measure accurately the P. expansum idh mRNA levels relative to the mRNA levels of three reference genes (18S, β-tubulin, calmodulin), taking into account important parameters such as PCR inhibition and multiple reference gene stability. Subsequently, two P. expansum field isolates and one reference strain were grown on apple puree agar medium (APAM) under three conditions of temperature and atmosphere: 20°C — air, 4°C — air and 4°C — controlled atmosphere (CA; 3% O2). When P. expansum strains reached a 0.5 and 2.0cm colony diameter, idh expression and patulin concentrations were determined by means of the developed RT-qPCR and an HPLC-UV method, respectively. The in vitro study showed a clear reduction in patulin production and down-regulation of the idh gene expression when P. expansum was grown under 4°C — CA. The results suggest that stress (low temperature and oxygen level) caused a delay of the fungal metabolism rather than a complete inhibition of toxin biosynthesis. A good correlation was found between the idh expression and patulin production, corroborating that temperature and atmosphere affected patulin production by acting at the transcriptional level of the idh gene. Finally, a reliable RT-qPCR can be considered as an alternative tool to investigate the effect of control strategies on the toxin formation in food.

Modeling Penicillium Expansum Growth Response to Thyme Essential oil at Selected Water Activities and pH Values Using Surface Response Methodology

Our objective was to evaluate, using a full factorial design, the effects of selected water activities (0.990, 0.945, or 0.900), pHs (5, 4, or 3), and thyme essential concentration (TEO, 0, 25, 50, or 100ppm) oil on Penicillium expansum lag time (λ) and radial growth rate (μm) obtained by modeling mold response using Gompertz equation, and corresponding polynomial quadratic models. Potato-dextrose agar formulated with every studied factor combination was inoculated with 103 spores/ml, and incubated at 25°C up to 30 days. Mold colony diameter was periodically measured during incubation and adjusted with Gompertz equation to determine λ and μm. Decreasing aw and pH, and increasing TEO concentration decreased μm and increased λ. At low aw and pH, the increase in TEO concentration had a dramatic effect on P. expansum response since 25ppm of TEO inhibited its growth for 30 days at 25°C. Gompertz parameters exhibited that P. expansum was sensitive to the evaluated combined factors, allowing us to construct a secondary predictive growth model. TEO in combination with aw and pH reduction effectively inhibited P. expansum growth.

A study on the physicochemical parameters for Penicillium expansum growth and patulin production: effect of temperature, pH, and water activity.

Penicillium expansum is among the most ubiquitous fungi disseminated worldwide, that could threaten the fruit sector by secreting patulin, a toxic secondary metabolite. Nevertheless, we lack sufficient data regarding the growth and the toxigenesis conditions of this species. This work enables a clear differentiation between the favorable conditions to the P. expansum growth and those promising for patulin production. A mathematical model allowing the estimation of the P. expansum growth rate according to temperature, a W, and pH, was also developed. An optimal growth rate of 0.92 cm/day was predicted at 24°C with pH level of 5.1 and high a W level of 0.99. The model's predictive capability was tested successfully on artificial contaminated apples. This model could be exploited by apple growers and the industrialists of fruit juices in order to predict the development of P. expansum during storage and apple processing.

Residue levels and performance of potassium sorbate and thiabendazole and their co-application against blue mold of apples when applied as water dip treatments at 20 or 53 °C

The efficacy of potassium sorbate (K-sorb) as an antifungal, alone or combined with thiabendazole (TBZ), and hot water at 53°C, was studied against blue mold on apples. Results demonstrated the fungistatic effect of K-sorb: 2000mgL−1 significantly reduced Penicillium expansum growth, and a 24h delay in fungi development was observed in the amended liquid culture. K-sorb at 1% significantly diminished decay incidence, especially when applied at 53°C. The performance of TBZ was not improved by the co-application of K-sorb. Treatments efficacy was related to K-sorb distribution on fruit surface. ESEM and X-ray qualitative spectra analyses revealed an irregular distribution of K-sorb over the fruit surface and areas with salt accumulation. K-sorb residues remained quite unchanged until 3 d of storage then they declined progressively. Their degradation was influenced by water temperature: it was faster on fruit treated at 53°C. An inverse relation between P. expansum growth and K-sorb concentration was observed. After 72h of incubation, P. expansum depleted 99% of K-sorb from liquid culture media.The low efficacy of K-sorb treatments against blue mold decay on apple fruit may be ascribed to the low persistence of K-sorb residues, to the irregular spatial distribution of the salt on the fruit surface, and the ability of P. expansum to degrade the salt.