Patulin Content Research Articles

Assessment of selenium-enriched deactivated probiotic yeast efficiency in patulin detoxification in apple juice

Patulin (PAT) contamination in fruits, particularly apples and their products, poses a significant health hazard. This research aimed to eliminate PAT from simulated juice solution and actual apple juice using live and ultrasonically deactivated (D) probiotic yeasts, specifically Saccharomyces cerevisiae (S.c) and Saccharomyces boulardii (S.b) yeasts enriched with selenium (Se). The Se-enriched yeasts were analyzed using various techniques including Fourier transform infrared spectrometer (FT-IR), energy-dispersive X-ray analysis (EDX), scanning electron microscopy (SEM), and Inductively coupled plasma–optical emission spectroscopy (ICP-OES). The study assessed the effects of yeast type, contact time (2–18 h), ultrasound treatment, and initial concentration of PAT (50–150 μg.L−1) on PAT adsorption. The most effective treatment involved the Se-S.b-D yeast strain, with an initial PAT concentration of 50 μg.L−1 for 10 h, exhibiting notable toxin removal percentages in both the apple juice simulator (98.27% reduction equivalent to 49.135 μg.L−1) and real apple juice (87.19%). The detoxification outcomes were consistent with pseudo-second-order kinetic and Langmuir isotherm models, indicating that Se-S.b-D is a biocompatible and low-cost strain with high efficiency to remove PAT in aqueous solutions.

Predictive modeling of patulin accumulation in apple lesions infected by Penicillium expansum using machine learning

Penicillium expansum causes blue mold in fruit, leading to the accumulation of patulin, a harmful toxin. Current detection methods for patulin are costly and complex, highlighting the need for a simplified approach. This study investigates the impact of P. expansum on ‘Golden Delicious’ and ‘Fuji’ apples, focusing on significant changes in lesion characteristics and fruit properties. Correlation analysis revealed strong positive associations between patulin content and lesion diameter, lesion depth, and fruit weight loss, while negative correlations were observed with apple firmness and flesh firmness. Of the four machine learning models used - Back Propagation Neural Network (BPNN), Random Forest (RF), Extreme Gradient Boosting (XGBoost) and Gradient Boosting Regression Tree (GBRT) - all showed good predictive performance without overfitting the data. BPNN outperformed the others in accurately predicting patulin accumulation (Golden Delicious: RMSE=0.72, MAE=0.217, R²=0.982; Fuji: RMSE=0.289, MAE=0.08, R²=0.994). Key features influencing patulin accumulation, identified using SHapley Additive exPlanation (SHAP) measures, included lesion diameter, lesion depth, and fruit weight loss. This research highlights the potential of machine learning to predict patulin accumulation based on these critical factors, providing a simplified detection method for postharvest fruit quality management.

Hannaella sinensis, a promising biocontrol agent for combating postharvest pear fruit diseases and patulin degradation

Postharvest pear fruits are susceptible to fungal decay and patulin (PAT) contamination during storage and transportation. PAT is a harmful mycotoxin contaminant of fruits and fruit products. Our team has identified a strain of Hannaella sinensis through preliminary research and validated its ability to degrade PAT in vitro. However, whether H. sinensis can effectively combat postharvest diseases of pears and control PAT within the fruit was yet unknown. Therefore, our current work aimed to determine the ability of H. sinensis to control blue mold decay and PAT contamination in postharvest pear fruit. The results showed that H. sinensis could effectively control postharvest blue mold decay, significantly reducing both the decay rate and lesion diameter in pear fruits and the PAT content in pear wounds. In addition, H. sinensis treatment had no negative impression on pear storage. H. sinensis was shown to have a better ability to adapt to the environment, occupy space, and utilize nutrients than pathogens, which provides favorable conditions for H. sinensis to colonize the wound and surface of pear fruit. The inhibitory effect of H. sinensis on PAT represents a new solution to control PAT contamination in food.

Emerging innovative pre‐ and post‐harvest management practices to mitigate patulin‐linked food safety risks in apple and its products

AbstractPatulin, a toxic secondary metabolite produced by certain molds (Penicillium, Aspergillus, and Byssochlamys), poses a significant health risk when present in apple juice products above permissible levels. Its presence is a major concern for both consumers and regulatory bodies due to its potential carcinogenic and mutagenic effects. Minimizing patulin concentration in apple juice products requires a multifaceted approach involving various stages of apple fruit production, from orchard management to processing and storage. This review explores the pre‐ and postharvest strategies associated with minimizing patulin concentration in apple juice products. It examines the role of good agricultural practices in reducing mold contamination in orchards and discusses the importance of proper postharvest handling, including fruit sorting and washing to remove contaminated apples before processing. During processing, factors such as temperature, pH, and processing time play crucial roles in minimizing patulin levels. Innovative processing technologies, such as pulsed electric fields (PEF), ultraviolet (UV) radiation, high‐pressure processing, enzymatic, and chemical degradation have shown promise in reducing patulin concentration while preserving the sensory and nutritional quality of the juice. Furthermore, effective storage practices, such as maintaining proper temperature and humidity levels, are essential for preventing patulin formation during storage. Continuous monitoring and analytical testing for patulin content throughout the production chain are necessary to ensure compliance with regulatory standards and to guarantee the safety of apple juice products. Despite advancements in technology and production practices, challenges remain in effectively minimizing patulin concentration. These include the need for further research to develop more efficient detection methods, the adoption of sustainable and eco‐friendly practices in orchard management, and the dissemination of knowledge and best practices to stakeholders across the apple juice supply chain. In conclusion, minimizing patulin concentration in apple juice products requires a holistic approach that integrates preventive measures, innovative processing technologies, and stringent quality control measures. By addressing these challenges, the apple juice industry can ensure the production of safe and high‐quality products that meet regulatory standards and consumer expectations.

Determination and analysis of patulin in apples, hawthorns, and their products by high-performance liquid chromatography.

This study aimed to establish a high-performance liquid chromatography (HPLC) method to investigate the residues of patulin in apples, hawthorns, and their products. A total of 400 samples were collected from online shopping plats and supermarkets in China, including apples (n = 50), hawthorns (n = 50), and their products (apple juice, apple puree, apple jam, hawthorn juice, hawthorn chips, and hawthorn rolls, n = 300). In this experiment, this method had good linearity and a recovery of 82.3-94.4% for patulin. The limit of detection (LOD) was 0.2µg/kg for liquid samples, while it was 0.3µg/kg for solid and semi-fluid samples. The frequencies of patulin were 79.8% in 400 samples, and the patulin concentration is from 0.6 to 126.0µg/kg. Two samples (0.5%) for patulin exceeded the regulatory limit (50µg/kg) in 400 samples. The frequencies of patulin in kinds of samples were 32.0-98.0% (p < 0.05), and the percentage of samples exceeding the limit was not more than 2.0%. The frequencies of patulin in domestic samples were 83.0%, while they were 57.7% in imported samples. Two domestic samples (0.6%) contained patulin above the regulatory limit, while none of the imported samples exceeded the limit. Among the online and offline samples, the frequencies of patulin were 76.4 and 82.1%. Two online samples (1.0%) for patulin exceeded the regulatory limit, whereas none of the offline samples exceeded the limit. These results showed it is important to monitor regularly the content of patulin in apples, hawthorns, and their products to ensure consumer food safety.

The Influence of Long-Term Storage on the Epiphytic Microbiome of Postharvest Apples and on Penicillium expansum Occurrence and Patulin Accumulation.

Patulin is a secondary metabolite primarily synthesized by the fungus Penicillium expansum, which is responsible for blue mold disease on apples. The latter are highly susceptible to fungal infection in the postharvest stages. Apples destined to produce compotes are processed throughout the year, which implies that long periods of storage are required under controlled atmospheres. P. expansum is capable of infecting apples throughout the whole process, and patulin can be detected in the end-product. In the present study, 455 apples (organically and conventionally grown), destined to produce compotes, of the variety "Golden Delicious" were sampled at multiple postharvest steps. The apple samples were analyzed for their patulin content and P. expansum was quantified using real-time PCR. The patulin results showed no significant differences between the two cultivation techniques; however, two critical control points were identified: the long-term storage and the deck storage of apples at ambient temperature before transport. Additionally, alterations in the epiphytic microbiota of both fungi and bacteria throughout various steps were investigated through the application of a metabarcoding approach. The alpha and beta diversity analysis highlighted the effect of long-term storage, causing an increase in the bacterial and fungal diversity on apples, and showed significant differences in the microbial communities during the different postharvest steps. The different network analyses demonstrated intra-species relationships. Multiple pairs of fungal and bacterial competitive relationships were observed. Positive interactions were also observed between P. expansum and multiple fungal and bacterial species. These network analyses provide a basis for further fungal and bacterial interaction analyses for fruit disease biocontrol.

A fluorescence aptamer sensor utilizing WS2 nanosheets for sensitive detection of patulin: enhanced specificity and wide applicability.

A tungsten disulfide (WS2) nanosheet-based aptamer sensor was developed to detect patulin (PAT). The 5'-end of the PAT aptamer was modified with a cyanine 3 (Cy3) fluorophore, which self-assembled on WS2 nanosheets. The interaction between the Cy3 fluorophore at the 5'-end of the PAT aptamer and the WS2 nanosheets resulted in reduced fluorescence (FL) intensity due to fluorescence resonance energy transfer (FRET). The introduction of PAT into this sensing system led to hybridization with the PAT aptamer, forming a G-quadruplex/PAT complex with low affinity for the WS2 nanosheet surface. This hybridization increased the distance between the Cy3 fluorophore and the WS2 nanosheets, inhibiting FRET and producing a strong FL signal. Under optimal experimental conditions, the FL intensity of the sensing system demonstrated an excellent linear correlation with PAT concentrations ranging from 0.5 to 40.0 ng mL-1, and it achieved a detection limit (S/N = 3) of 0.23 ng mL-1. This sensing system offers enhanced specificity for PAT detection and has the potential for broad application in detecting other toxins by substituting the sequence of the recognition aptamer.

Genetic identification, pathogenicity and patulin production of Penicillium species from apple blue mold in China

Abstract Objectives Blue mold is a common postharvest disease that leads to severe rot and patulin (PAT) contamination in fruits, which is a key factor endangering the storage and quality of apple products. However, the Penicillium species from apple blue mold in China and their pathogenicity and PAT production ability have not been well studied. Materials and Methods In this study, 62 strains of pathogenic Penicillium species were isolated from blue mold apples collected from different regions of China. The ITS, BenA, and CaM genes were sequenced for molecular identification. Results Penicillium strains were identified as three species, 57 P. expansum, 3 P. crustosum, and 2 P. polonicum. Twelve variants of the ITS sequence, 61 variants of BenA and 67 variants of CiaM genes were identified between Penicillium species. Fungal morphology was observed on potato dextrose agar (PDA). After 10 d of cultivation, P. expansum cultures were detected with PAT concentrations ranging from 457.98 to 1333.85 mg/kg, and two P. polonicum strains were 6.02 mg/kg and 6.30 mg/kg. The three P. crustosum strains could not produce PAT on PDA. In apple inoculation, P. expansum strains showed significantly faster infection rates than P. crustosum and P. polonicum strains. All P. expansum strains can produce PAT during infection, and the concentrations in the rot apple tissues were 2.31–88.67 mg/kg. The P. crustosum and P. polonicum strains could not produce PAT during infection. Conclusions This study provides data and information regarding the morphology, virulence and PAT production of Penicillium pathogens that will improve the understanding of apple blue mold and postharvest disease control.

Structural switching aptamer-based electrochemical sensor for mycotoxin patulin detection

In this study, an electrochemical and aptamer-based aptasensor was developed for the sensitive detection of patulin, a mycotoxin commonly found in fruits and fruit-based products. The aptasensor used an innovative structural switching signal-off platform for detecting patulin. The aptamer immobilization on screen-printed carbon electrodes was achieved through Au electrodeposition and thiol group (-SH) route. Response surface methodology was used to determine the optimal incubation times for the aptamer, blocking agent, and target molecule, which were found to be 180 min, 40 min, and 89 min, respectively. The response of the aptamer to different concentrations of patulin was measured using square wave voltammetry by exploiting the structural switching mechanism. The sensor response was determined by quantifying differences in the aptasensor's background current. The aptasensor exhibited a linear working range of 1–25 μM and a low detection limit of 3.56 ng/mL for patulin. The aptasensor's relative standard deviation and accuracy were determined to be 0.067 and 94.4%, respectively. A non-specific interaction was observed at low concentrations of two other mycotoxins, ochratoxin A and zearalenone. The interference from ochratoxin A in the measurements was below 10%. In real sample tests using apple juice, interference, particularly at low concentrations, had changed the recovery of patulin negatively with a significant effect on the structural switching behavior. Nevertheless, at a concentration of 25 ng/mL, the interference effect was eliminated, and the recovery standard deviation improved to 6.6%. The aptasensor's stability was evaluated over 10 days, and it demonstrated good performance, retaining 13.12% of its initial response. These findings demonstrate the potential of the developed electrochemical aptasensor for the sensitive detection of patulin in fruit-based products, with prospects for application in food safety and quality control.

Temperature-induced metabolic changes of apples infected with Penicillium expansum characterized by non-targeted high-resolution mass spectrometry

Blue mold caused by Penicillium expansum is a prevalent postharvest disease that affects quality of apples during storage and transportation and is responsible for considerable, economic losses to the apple industry. Patulin (PAT), a secondary metabolite of P. expansum, is toxic and widely found in apples and their products, which is hazardous to human health. In this study, Fuji apples were inoculated with P. expansum then subjected to both room-temperature storage and cold storage. Measurements of the lesion diameter and PAT content revealed that the growth rate of P. expansum was lower during cold storage but the PAT content was higher, even in samples with the same lesion diameter. Non-targeted high-resolution mass spectrometry was employed to examine the metabolic changes in the infected tissues for a fixed lesion diameter (after 24 d of cold storage and 7 d of room-temperature storage). Clear differences were observed in the contents of organic acids, lipids, flavonoids, sugars, and other metabolites. Compared with the apples stored at room temperature, downregulation of metabolic pathways related to disease resistance and upregulation of those related to PAT synthesis at cold storage. The obtained results further elucidate the effects of temperature on P.expansum infection and apple resistance, thus providing a theoretical basis for the prevention and control of this problematic plant pathogen.

Overexpression of the SDR gene improves the ability of Meyerozyma guilliermondii to degrade patulin in pears and juices.

The intracellular enzymes of antagonistic yeast are effective in controlling patulin (PAT) contamination. However, countless enzymes that have been revealed remain functionally uncharacterized. The study built on previous transcriptomic data obtained by our research group to amplify and express a gene encoding a short-chain dehydrogenase/reductase (SDR) in Meyerozyma guilliermondii. Overexpression of SDR increased the tolerance of M. guilliermondii to PAT and the ability to degrade PAT of the intracellular enzymes. Furthermore, MgSDR-overexpressed M. guilliermondii showed higher PAT degradation in juices (apple and peach) and controlled the blue mold of pears at 20°C and 4°C while significantly reduced the content of PAT and the biomass of Penicillium expansum in decayed tissues than wild-type M. guilliermondii. This study provides theoretical references for the subsequent heterologous expression, formulation, and application of the SDR protein from M. guilliermondii and contributes to elucidating the PAT degradation mechanism of antagonistic yeasts.

A novel ECL aptasensor for ultra-highly sensitive detection of patulin based on terbium organic gels as Co-reaction accelerator in a 3, 4, 9, 10-perylenetetracarboxylic acid/K2S2O8 system

Patulin (PAT), a fungal metabolite, which mainly exists in various moldy fruits, is greatly harmful to human. However, there are still many unsolved problems in the current detection of PAT. In the work, an ultra-highly sensitive and effective monitoring strategy for PAT was explored based on a novel electrochemiluminescence (ECL) aptasensor. Here, 3, 4, 9, 10-perylenetetracarboxylic acid (PTCA) was chosen as luminophore and terbium (Tb) metal organic gel (MOG) was prepared as a co-reaction accelerator. The MOG displayed a large surface area for immobilization of sufficient PTCA to catalyze co-reactant K2S2O8 to generate more sulfate radical anions (SO4• −), thus accelerating the electron-transfer (ET) rate to facilitate ECL efficiency. In the presence of PAT, the ECL signal was greatly quenched, which could be attributed to the specific binding effect between PAT aptamer and PAT. Based on this process, a wide range of PAT concentrations from 0.1 fg·mL−1 to 0.1 μg·mL−1 and a low detection limit of 0.02 fg·mL−1 (S/N = 3) were analyzed. The aptasensor showed excellent detection properties for trace patulin in terms of selectivity, sensitivity, stability, reproducibility and practicability. The designing ideas could serve as a model for the application of metal organic gels to design ultra-highly sensitive ECL platforms for food safety.

Fast Screening Test of Apple Juice and Surface Water for Patulin Recognition and Quantification

Since a high concentration of patulin causes cytotoxicity, a new approach to the determination of patulin plays an important role in the research and development of new control technologies. The main objective of the paper is to provide a fast screening method for obtaining clean water and high-quality apple juice. Square-wave voltammetry method using a modified Mn (OAP) Cl screen-printed carbon electrode was used for the fast screening test of apple juice and surface water for patulin recognition and quantification. A number of experimental parameters, such as scan rate, type of buffer solution, and pH, were studied and optimized. Thus, a linear concentration dependence was determined in the range 1.00 × 10–12 to 1.00 × 10–8 mol L–1, while the quantification limit was 1.00 × 10–12 mol L–1 and the detection limit was 3.33 × 10–13 mol L–1. High reliability was achieved at the assay of patulin in water and apple juice samples, with a recovery rate of 96.27–99.88%, relative standard deviation (RSD), and a bias value of less than 5.00%. Based on the remarkable outcomes, it can be inferred that the sensor holds promise as a robust instrument for point-of-care detection in the times ahead.

Aggressiveness and Patulin Production in Penicillium expansum Multidrug Resistant Strains with Different Expression Levels of MFS and ABC Transporters, in the Presence or Absence of Fludioxonil.

Penicillium expansum is the most common postharvest pathogen of apple fruit, causing blue mold disease. Due to the extensive use of fungicides, strains resistant to multiple chemical classes have been selected. A previous study by our group proposed that the overexpression of MFS (major facilitator superfamily) and ABC (ATP binding cassette) transporters constitute an alternative resistance mechanism in Multi Drug resistant (MDR) strains of this pathogen. This study was initiated to determine two main biological fitness parameters of MDR strains: aggressiveness against apple fruit and patulin production. In addition, the expression pattern of efflux transporters and hydroxylase-encoding genes that belong to the patulin biosynthesis pathway, in the presence or absence of fludioxonil and under in vitro and in vivo conditions were investigated. Results showed that the MDR strains produced higher concentrations of patulin but showed a lower pathogenicity compared to the wild-type isolates. Moreover, expression analysis of patC, patM and patH genes indicated that the higher expression levels do not correlate with the detected patulin concentration. The selection of MDR strains in P. expansum populations and the fact that they produce more patulin, constitutes a serious concern not only for successful disease control but also for human health. The above-mentioned data represent the first report of MDR in P. expansum associated with its patulin-production ability and the expression level of patulin biosynthesis pathway genes.

Implementation of the HACCP System for Apple Juice Concentrate Based on Patulin Prevention and Control.

Patulin (PAT) is a toxic secondary metabolite produced by Aspergillus sp. and Penicillium sp., which acts as a contaminant of most apples and their products. The internationally recognized HACCP system is selected as the theoretical basis to more effectively reduce the PAT in apple juice concentrate (AJC). Through field investigation of apple juice concentrate (AJC) production enterprises, we collected 117 samples from 13 steps of AJC production, including whole apple, apple pulp, and apple juice. PAT contents were analyzed via high-performance liquid chromatography (HPLC) and compared with samples from the different production processes. The result demonstrated that the PAT content was significantly (p < 0.05) influenced by five processes, receipt of raw apples, sorting of raw apples, adsorption step, pasteurization, and aseptic filling. These processes were determined as the CCPs. Monitoring systems for maintaining CCPs within acceptable limits were established, and corrective actions were proposed in case a CCP was surpassed. Based on the above-identified CCPs, critical limits, and control methods (corrective actions), a HACCP plan related to the production process of AJC was established. This study provided important guidance for juice manufacturers wishing to effectively control the PAT content in their products.

Efficient Biodegradation of Patulin by Aspergillus niger FS10 and Metabolic Response of Degrading Strain.

Patulin, a mycotoxin commonly found in fruits and derived products, causes serious health problems for humans and animals worldwide. Several microbial strains have been observed to possess the ability to effectively remove patulin. However, these methods are presently associated with disadvantages such as low degradation efficiency and an unclear biodegradation mechanism. In the current study, the characteristics of patulin degradation via Aspergillus niger FS10 were evaluated, and the mechanisms involved were analyzed using metabolomics technologies. The results showed that the suspension of A. niger FS10 could degrade 94.72% of patulin within 36 h. The moment concentration pf patulin was 0.116 μg/mL, and the detection limit value was 0.01 μg/mL. In addition, the patulin content was reduced to levels below the detection limit within 48 h. A. niger FS10 mainly degrades patulin by producing intracellular enzymes, which can convert patulin into ascladiol. This degradation method can effectively reduce the damage caused by patulin to HepG2 cells. In addition, the patulin treatment significantly affects the pentose phosphate pathway and the glutathione pathway. These two metabolic pathways are speculated to be closely related to patulin degradation via A. niger FS10. The incubation of A. niger FS10 with patulin-contaminated apple pomace can not only eliminate patulin but also increase the utilization of apple pomace. Therefore, our research results provide a new method for addressing patulin contamination in the food and feed industries.

A SIMPLE AND SELECTIVE METHOD FOR SIMULTANEOUS DETERMINATION OF PATULIN AND 5- HMF IN HONEY AND APPLE JUICE BY HPLC-UV

A selective and sensitive method using a high-performance liquid chromatography-UV detector (HPLC-UV) for the simultaneous determination of Patulin (PAT) and 5-(hydroxymethyl)furfural (5-HMF) in honey and apple juice was developed. The sample preparation technique QuEChERS was applied to increase the sensitivity and selectivity. The linear ranges for PAT and 5-HMF detected by the method were 2.0 ppb ÷ 200.0 ppb and 2.0 ppm ÷ 20 ppm. The results of method validation show that the recovery efficiency for PAT ranged from 92.8% ÷ 98.2% with % RSDr from 0.56% ÷ 0.63% and from 97.9% ÷ 101.2% with %RSD 0.39% ÷ 0.67% for 5-HMF and LOD and LOQ values of the method for PAT and 5-HMF detection were respectively: 0.6 and 2.0 ppb; 0.6 and 2.0 ppm. The influence of the matrix effect on the accuracy, repeatability, and recovery of the method was insignificant. The proposed method was applied to quantify the content of PAT, and 5-HMF in actual samples, collected in Ho Chi Minh City, Vietnam. The result showed that PAT was not found in honey samples but was detected in 5 of 10 apple juice samples. In addition, 5-HMF was detected in 3 of 10 honey samples and 10 of 10 apple juice samples.

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.

Small GTPases RasA and RasB regulate development, patulin production, and virulence of Penicillium expansum

Ras GTPases belong to one of the small G proteins, which regulate morphology and growth of filamentous fungi. However, whether Ras GTPases are involved in the biological process of Penicillium expansum remains unclear. In this study, RasA and RasB gene knockout mutants of P. expansum were constructed. ΔPeRasA and ΔPeRasB showed defective growth, insufficient spore development and malformed mycelium. Loss of PeRasA and PeRasB resulted in a markedly reduction of patulin content and a down-regulation genes expression involved in patulin biosynthesis. Deletion of PeRasA and PeRasB significantly down-regulated the expression of MAPK and cAMP signal regulators. Additionally, ΔPeRasA and ΔPeRasB exhibited attenuated virulence on apple and pear fruit and lower gene expression of cell wall degrading enzymes. In summary, PeRasA and PeRasB were involved in the development, patulin synthesis and virulence of P. expansum by controlling MAPK and cAMP signaling pathways.

Biological control of blue mold rot in apple by Kluyveromyces marxianus XZ1 and the possible mechanisms of action

The yeast Kluyveromyces marxianus was permitted for direct addition to food and shown antagonistic ability against some pathogens. However, the effect and detailed mechanism of K. marxianus on control blue mold disease and patulin accumulation in apple remain unknown. In our study, K. marxianus XZ1 reduced the disease incidence and patulin content in apple caused by Penicillium expansum at 3 d after incubation compared with the control, which is decreased by 51% and 52%, respectively. Studies on the potential mechanisms of action revealed that (1) K. marxianus XZ1 adhered well to the apple wound to gain a competitive advantage; (2) antibacterial substances produced by K. marxianus XZ1 under the stimulation of P. expansum to inhibit the growth of this fungus; (3) activity of catalase, peroxidase, polyphenoloxidase, chitinase, and phenylalanine ammonialyase was activated to participate in the defense of fruit against P. expansum; (4) the expression levels of some genes involved in plant hormone signal transduction, including salicylic acid, jasmonate acid and ethylene signaling pathway, were upregulated to strengthen the fruit's defense against mold. Taken together, our results indicated that K. marxianus XZ1 may serve as a potential biological agent against postharvest decay and patulin contamination caused by P. expansum in apple fruit, mainly attributed to its ability of competition for space and nutrients, secretion of antifungal components, parasitism and activation of plant hormone signal transduction.