Qiya Yang

Ascorbic Acid Enhances Oxidative Stress Tolerance and Biological Control Efficacy of Pichia caribbica against Postharvest Blue Mold Decay of Apples

The effect of ascorbic acid (VC) on improving oxidative stress tolerance of Pichia caribbica and biocontrol efficacy against blue mold caused by Penicillium expansum on apples was investigated. P. caribbica showed susceptibility to the oxidative stress in vitro test, and 250 μg/mL VC treatment improved its oxidative stress tolerance. The higher viability exhibited by VC-treated yeast was associated with a lower intracellular ROS level. The activities of antioxidant enzymes of P. caribbica were improved by VC treatment, including catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPX). Additionally, VC-treated yeast exhibited greater biocontrol activity against P. expansum and faster growth when stored at 25 and 4 °C, respectively, compared to the performance of the non-VC-treated yeast. In response to the VC treatment under oxidative stress, several differentially expressed proteins were identified in P. caribbica, and most of the poteins were confirmed to be related to basic metabolism. Therefore, the application of ascorbic acid is a useful approach to improve oxidative stress tolerance of P. caribbica and its biocontrol efficacy on apples.

Biological Control of Patulin by Antagonistic Yeast: A case study and possible model

Abstract The occurrence of patulin in fresh apples and apple products is a great burden from health, safety and economic perspectives. Attempts to prevent patulin accumulation in fruits might lead to the excessive use of fungicides. Therefore, guaranteeing the safety of apple foods is crucial for the international apple industry. Recently, literature revealed that application of antagonistic yeasts and other BCAs have been able to disrupt the process of fungal infection and patulin production in apples. Although, over the years the effect of interaction between BCAs and fungi on patulin production has been reported, the exact mechanism(s) of their action remain unclear. Here, the review focused on toxicology and occurrence of PAT; research advances made over the past few years on the interaction between antagonistic yeast, fruits and patulin-producing fungi; the prevalence of patulin in apple fruits and products and the implications of synthetic-fungicide applications. In addition, attention was focused on the mechanism(s) and the enhancement of the biocontrol efficacy of antagonistic for patulin control.

The Possible Mechanisms Involved in Degradation of Patulin by Pichia caribbica

In this work, we examined the mechanisms involved in the degradation of patulin by Pichia caribbica. Our results indicate that cell-free filtrate of P. caribbica reduced patutlin content. The heat-killed cells could not degrade patulin. However, the live cells significantly reduced the concentration of the patulin. In furtherance to this, it was observed that patulin was not detected in the broken yeast cells and cell wall. The addition of cycloheximide to the P. caribbica cells decreased the capacity of degradation of patulin. Proteomics analyses revealed that patulin treatment resulted in an upregulated protein which was involved in metabolism and stress response processes. Our results suggested that the mechanism of degradation of patulin by P. caribbica was not absorption; the presence of patulin can induce P. caribbica to produce associated intracellular and extracellular enzymes, both of which have the ability to degrade patulin. The result provides a new possible method that used the enzymes produced by yeast to detoxify patulin in food and feed.

Biodegradation of zearalenone by Saccharomyces cerevisiae: Possible involvement of ZEN responsive proteins of the yeast.

UNLABELLEDnThe mycotoxin zearalenone, also known as F-2 mycotoxin or RAL is a potent estrogenic metabolite produced by some Gibberella and Fusarium species. It is a common contaminant of cereal crops, livestock and poultry products. However, detoxification of zearalenone (ZEN) remains a challenge. Recently, biological approach for ZEN detoxification is being explored. In this study, we investigated the biodegradation of ZEN by using Saccharomyces cerevisiae and the possible mechanisms involved. The findings revealed that, after 48h of incubation of S. cerevisiae in combination with ZEN, the ZEN was completely degraded by S. cerevisiae. On the contrary, heat-killed cells and cell-free culture filtrates of S. cerevisiae could not degrade ZEN. Furthermore, addition of cycloheximide to S. cerevisiae combined with ZEN at time 0h prevented ZEN degradation, while addition of cycloheximide at 12h significantly slowed down degradation. The results also indicated cellular proteomics of S. cerevisiae. Several differential proteins were identified, most of which were related to basic metabolism.nnnBIOLOGICAL SIGNIFICANCEnThe findings revealed that, after 48h of incubating ZEN together with S. cerevisiae, ZEN was completely degraded by S. cerevisiae. The mechanisms involved in the degradation of ZEN by S. cerevisiae may be the production of associated intracellular and extracellular enzymes, which have the ability to degrade ZEN. In addition, there were some functional proteins produced by S. cerevisiae, indicating that the basic metabolism of S. cerevisiae was improved when ZEN was added. This novel discovery by the authors, will greatly contribute to the field of biodegradation of mycotoxin by antagonists. The authors also believed this innovation will open the grounds for further research and improvement of S. cerevisiae in the field of biodegradation.

Phytic Acid Enhances Biocontrol Activity of Rhodotorula mucilaginosa against Penicillium expansum Contamination and Patulin Production in Apples

The effect of Rhodotorula mucilaginosa in combination with phytic acid (PA) on blue mold decay and patulin contamination of apples was investigated. Results from this study show that different concentrations of PA were effective in reducing the disease incidence of apples and that PA at concentration of 4 μmol/mL, decreased the incidence of blue mold decay in apples from 86.1 to 62.5%, and showed higher control efficacy compared to untreated, control fruit during storage at 20°C. However, R. mucilaginosa combined with PA (4 μmol/mL) showed better control efficacy of blue mold decay than R. mucilaginosa used as single treatment, the disease incidence was reduced to 62.5% and lesion diameter on apples was reduced to 16.59 cm. In in vitro experiments, the addition of PA enhanced the biocontrol effect of R. mucilaginosa against the growth of Penicillium expansum and reduced patulin level when compared with either R. mucilaginosa or PA used separately. R. mucilaginosa together with PA, improved the inhibition of patulin production in wounded apples, decreasing the content of patulin by 89.6% compared to the control, under experimental conditions. Both R. mucilaginosa and R. mucilaginosa in combination with PA degraded patulin in vitro. In conclusion, the appropriate combination of R. mucilaginosa and PA may provide an effective biocontrol method for reducing postharvest decay of apples.

Preparation, characterization and antibacterial activity of octenyl succinic anhydride modified inulin

Octenyl succinic anhydride modified inulin (In-OSA) was synthesized via chemical modification of inulin with octenyl succinic anhydride (OSA). The esterification of inulin with OSA was confirmed by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and degree of substitution (DS) calculation. Antibacterial activity of In-OSA against Staphylococcus aureus and Escherichia coli was investigated by minimum inhibitory concentration (MIC) and inhibition rate determination. The results showed that inhibition rates against both E.coli and S. aureus increased with the increase of the In-OSA concentration. And the MICs against E. coli and S. aureus were 1% and 0.5% (w/v), respectively. The antibacterial mechanism was analyzed with the results of the proteins and nucleic acids leakage, SEM and negative staining transmission electron microscopy (TEM). Both the leakages of proteins and nucleic acids increased with the increase of the In-OSA concentration. The leakage occurred mainly in the early stage which indicated that cell membrane and wall were destroyed by In-OSA quickly. The images of SEM and negative staining TEM suggested that the cell membranes and cell walls of S. aureus were damaged more severely and even destroyed completely; but only pores appeared on the surface of E. coli.

Burdock fructooligosaccharide enhances biocontrol of Rhodotorula mucilaginosa to postharvest decay of peaches

The influence of adding burdock fructooligosaccharide (BFO) in the culture media on the efficacy of Rhodotorula mucilaginosa in controlling postharvest decay of peaches and its possible mode of action were investigated. The antagonistic activity of R. mucilaginosa to Rhizopus decay and blue mold decay of peaches was greatly enhanced through cultivation in the nutrient yeast dextrose agar (NYDA) medium amended with BFO at the concentration of 0.32%, compared with that cultivated in NYDB without BFO. R. mucilaginosa at 1×10(8) cells/mL cultivation in the NYDB media did not reduce the natural decay incidence of peaches, compared with the control after 30 d at 4 °C followed by 7d at 20 °C. However, R. mucilaginosa cultivation in the NYDB media amended with BFO at the concentration of 0.32% reduced the natural decay incidence of peaches. The population of R. mucilaginosa harvested from NYDB amended with BFO at 0.32% increased rapidly in peach wounds compared to that harvested from NYDB without BFO no matter peaches were stored at 20 °C or 4 °C. The activities of chitinase and β-1,3-glucanase of cell-free culture filtrate of R. mucilaginosa harvested from NYDB amended with BFO at 0.32% were higher than that at other concentrations and the control.

Investigating Proteome and Transcriptome Defense Response of Apples Induced by Yarrowia lipolytica

A better understanding of the mode of action of postharvest biocontrol agents on fruit surfaces is critical for the advancement of successful implementation of postharvest biocontrol products. This is due to the increasing importance of biological control of postharvest diseases over chemical and other control methods. However, most of the mechanisms involved in biological control remain unknown and need to be explored. Yarrowia lipolytica significantly inhibited blue mold decay of apples caused by Penicillium expansum. The findings also demonstrated that Y. lipolytica stimulated the activities of polyphenoloxidase, peroxidase, chitinase, l-phenylalanine ammonia lyase involved in enhancing defense responses in apple fruit tissue. Proteomic and transcriptomic analysis revealed a total of 35 proteins identified as up- and down-regulated in response to the Y. lipolytica inducement. These proteins were related to defense, biotic stimulus, and stress responses, such as pathogenesis-related proteins and dehydrin. The analysis of the transcriptome results proved that the induced resistance was mediated by a crosstalk between salicylic acid (SA) and ethylene/jasmonate (ET/JA) pathways. Y. lipolytica treatment activated the expression of isochorismate synthase gene in the SA pathway, which up-regulates the expression of PR4 in apple. The expression of 1-aminocyclopropane-1-carboxylate oxidase gene and ET-responsive transcription factors 2 and 4, which are involved in the ET pathway, were also activated. In addition, cytochrome oxidase I, which plays an important role in JA signaling for resistance acquisition, was also activated. However, not all of the genes had a positive effect on the SA and ET/JA signal pathways. As transcriptional repressors in JA signaling, TIFY3B and TIFY11B were triggered by the yeast, but the gene expression levels were relatively low. Taken together, Y. lipolytica induced the SA and ET/JA signal mediating the defense pathways by stimulating defense response genes, such as peroxidase, thaumatin-like protein, and chitinase 4-like, which are involved in defense response in apple. [Formula: see text]

Chitin enhances biocontrol of Rhodotorula mucilaginosa to postharvest decay of peaches

Biological control using microbial antagonists is a promising alternative approach to synthetic fungicides. However, effective biological control requires enhancing the consistency and efficacy of the antagonists used to control postharvest diseases. This study investigated the effect of chitin on the biocontrol efficacy of Rhodotorula mucilaginosa against blue mold and Rhizopus decay of peaches and on the protein expression profiles of R. mucilaginosa. The antagonistic activity of R. mucilaginosa harvested from the nutrient yeast dextrose broth (NYDB) with 0.5% chitin added was significantly improved compared with culture in NYDB without chitin. The R. mucilaginosa population cultured in chitin-supplement NYDB and nutrient yeast chitin borth (NYCB) harvested from peach wounds was more than that of R. mucilaginosa cultured in NYDB without chitin throughout the storage period except at 1 d. The protein expression profiles findings revealed that there were several differentially expressed proteins of R. mucilaginosa in the 0.5% chitin-supplemented NYDB and NYCB compared with that of R. mucilaginosa in NYDB. Most of these were cellular proteomes relating to the primary metabolic reactions such as glycoside hydrolases, phosphoribosyl pyrophosphate, and NADH dehydrogenases. Some proteins were also related to signal transmission and stress response.

Ochratoxin A is degraded by Yarrowia lipolytica and generates non-toxic degradation products

The mycotoxin ochratoxin A (OTA) is a common contaminant of various plant-derived foods and feeds. However, methods for complete decontamination remain to be established. Recently, biological approaches for mycotoxin removal using various species of yeast have been explored. In the present study, we investigated the efficacy of OTA degradation by the yeast Yarrowia lipolytica under various conditions, altering yeast concentration, temperature, pH, and concentration of OTA in order to determine the optimal requirements of this species. At a yeast concentration of 108 cells/ml, the degradation rate was higher than that observed at any other concentration and, after 24 h, the OTA concentration was reduced to almost half of the initial level introduced to the culture. Further, Y. lipolytica cultured at 28 °C showed the highest level of OTA degradation. Similarly, the culture performed optimally at a pH of 4. The initial concentration of OTA also affected the ability of the yeast to degrade OTA, with the level...