Octanal enhances disease resistance in postharvest citrus fruit by the biosynthesis and metabolism of aromatic amino acids.

Octanal was found to be able to reduce green mold incidence in citrus fruit by a defense response mechanism. However, the underlying mechanism remains largely unclear. Herein, the metabolomics, RNA-seq and biochemical analyses were integrated to explore the effect of octanal on disease resistance in harvested citrus fruit. Results showed that octanal fumigation at 40 µL L-1 was effective in controlling citrus green mold. Metabolomics analysis showed that octanal mainly led to the accumulation of some plant hormones including methyl jasmonate, abscisic acid, indole-3-butyric acid, indoleacetic acid (IAA), salicylic acid, and gibberellic acid and many phenylpropanoid metabolites including cinnamyl alcohol, hesperidin, dihydrokaempferol, vanillin, quercetin-3-O-malonylglucoside, curcumin, naringin, chrysin, coniferin, calycosin-7-O-ß-D-glucoside, trans-cinnamaldehyde, and 4',5,7-trihydroxy-3,6-dimethoxyflavone. Particularly, IAA and hesperidin were dramatically accumulated in the peel, which might be the contributors to the resistance response. Additionally, transcriptome analysis showed that octanal greatly activated the biosynthesis and metabolism of aromatic amino acids. This was further verified by the accumulation of some metabolites (shikimic acid, tryptophan, tyrosine, phenylalanine, IAA, total phenolics, flavonoids and lignin), increase in some enzyme activities (phenylalanine ammonia-lyase, tyrosine ammonia-lyase, 4-coumarate CoA ligase, cinnamic acid 4-hydroxylase, polyphenol oxidase, and peroxidase), up-regulation of some genes (tryptophan pyruvate aminotransferase, aldehyde dehydrogenase, shikimate kinase and shikimate dehydrogenase) expressions and molecular docking results. Thus, these results indicate that octanal is an efficient strategy for the control of postharvest green mold by triggering the defense response in citrus fruit.

Berberine hydrochloride delays citrus sour rot mainly by disrupting carbohydrate and energy metabolism of Geotrichum citri-aurantii spores.

Citrus sour rot is a common postharvest citrus disease caused by Geotrichum citri-aurantiiti, which has led to enormous economic losses, particularly during rainy seasons. In this study, we aimed to clarify the impact of berberine hydrochloride (BH), the hydrochloride form of an isoquinoline alkaloid, on the control efficiency of citrus sour rot and its antifungal mode against G. citri-aurantii. Results demonstrated that BH markedly impede the propagation of G. citri-aurantii by delaying the spores development from dormant stage into swollen and germinating stages, with the MIC and MFC value of 0.08 and 0.16 g L-1, respectively. When the artificially inoculated citrus fruit in control group were totally rotted, the disease incidence of BH-treated groups decreased by 35.00%-73.30%, which effectively delayed the disease progression and almost did not negatively affect fruit quality. SEM observation, CFW and PI staining images revealed that BH caused significant damage to both the cell membrane and cell wall of G. citri-aurantii spores, whereas only the cell membrane of the mycelium was affected. The impact of cell wall was related to the block of chitin and ß-1,3-glucan synthesis. Transcriptome results and further verification proved that 0.5 × MIC BH treatment affected the glycolysis pathway and TCA cycle mainly by inhibiting the production of acetyl-CoA and pyruvate. Subsequently, the activities of key enzymes declined, resulting in a further decrease in ATP levels, ultimately inhibiting the germination of spores. In conlusion, BH delays citrus sour rot mainly by disrupting carbohydrate and energy metabolism of G. citri-aurantii spores.

Integrated transcriptomic-metabolomic analysis reveals that cinnamaldehyde exposure positively regulates the phenylpropanoid pathway in postharvest Satsuma mandarin (Citrus unshiu).

Previously, wax + cinnamaldehyde (WCA) was proven to be able to effectively alleviate fruit decay and induce resistance in harvested Satsuma mandarin (Citrus unshiu). However, the potential molecular mechanism is largely unknown. In the present study, transcriptomics, metabolomics and biochemical analyses were combined to clarify this process. Transcriptomic analysis revealed that the expression of genes involved in secondary metabolites and related to pathogenesis and the phenylpropanoid pathway were significantly influenced by WCA treatment. In addition, metabolite profiling revealed that metabolites in the phenylpropanoid pathway were also predominantly impacted after WCA treatment. Correspondingly, enzymatic activities and gene expression involved in the phenylpropanoid pathway were positively regulated, especially in the first 24 h, resulting in increased levels of total phenolics, flavonoids and other secondary metabolites. Fruit inoculation experiments showed that WCA treatment significantly reduced the development of citrus green mold and sour rot while having no adverse effects on the edible quality of the tested citrus fruit. Our study confirms the potential role of WCA exposure in citrus to induce resistance through the phenylpropanoid pathway.

γ-Cyclodextrin encapsulated thymol for citrus preservation and its possible mechanism against Penicillium digitatum.

The volatility of essential oils greatly limits their industrial applications. Here, we successfully prepared γ-cyclodextrin (γ-CD) inclusion compounds (γ-CDTL) containing thymol (TL) for the control of green mold caused by Penicillium digitatum (P. digitatum) in citrus fruit. In vitro experiment showed that the minimum fungicidal concentration (MFC) of γ-CDTL against the hyphae growth of P. digitatum was 2.0 g/L, and 8 × MFC treatment significantly reduced the occurrence of green mold in citrus fruit and had no adverse effect on fruit quality in vivo test compared to prochloraz. Scanning electron microscopy (SEM), x-ray diffraction (XRD), fourier transform-infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), physical properties and sustained release properties were also performed, results indicated that the hydrogen bonds between TL and γ-CD were the basis for the formation of γ-CDTL. We further investigated the inhibition mechanism of γ-CDTL. SEM and TEM experiments showed that γ-CDTL treatment caused severe damage to the hyphal morphology and cells in 30 min and disrupted the permeability of P. digitatum mycelial cell walls by increasing the chitinase activity, thus accelerating the leakage of intracellular lysates. However, the integrity of the cell membrane was obviously damaged only after 60 min of treatment. In conclusion, we prepared a novel inclusion complex γ-CDTL with obvious antifungal effects and preliminarily elucidated its inclusion mechanism and antifungal mechanism. γ-CDTL might be a potent alternative to chemical fungicides for controlling the postharvest decay of citrus.

A combination of cinnamaldehyde and citral greatly alleviates postharvest occurrence of sour rot in citrus fruits without compromising the fruit quality.

One of the most troublesome postharvest diseases of citrus fruits is sour rot, caused by Geotrichum citri-aurantii. Sour rot reduces the shelf life of the fruits leading to massive economic losses. This study investigated the potential for a combination of cinnamaldehyde and citral (CC; 1: 2, v/v) at reducing the incidence of sour rot postharvest and its possible effect on fruit quality. Our findings show that CC could totally inhibit germination of G. citri-aurantii spores, with the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) both being 0.80 mL L-1. The combination (CC) acted against G. citri-aurantii by targeting the chitin content of the cell wall. Wax + CC (WCC; 1 × MFC) treatment also showed high efficiency in reducing the incidence of sour rot, which was 40% lower than in the control group by day 8 when all the fruits in the latter were rotten. Apart from vitamin c (Vc) content which was higher in the test group than in the control group, WCC treatment did not have any significant effect on the quality of the citrus fruits, the examined fruit quality parameters being weight loss rate, coloration index, firmness, pH, total soluble solid (TSS) content, Vc content, as well as solid acid ratio. These results indicate that the combination of cinnamaldehyde and citral (CC, 1: 2, v/v) can be used as a natural preservative to alleviate the progress of sour rot in citrus fruits postharvest.

Cinnamaldehyde promotes the defense response in postharvest citrus fruit inoculated with Penicillium digitatum and Geotrichum citri-aurantii.

Induced resistance in harvested fruit and vegetables is a superior strategy to reduce postharvest decay. In the present study, Cinnamaldehyde (CA) was applied to investigate for its induced resistance against Penicillium digitatum and Geotrichum citri-aurantii. The results showed that 5250 mg CA/L wax was effective concentration in inducing the resistance of citrus fruit to green mold and sour rot. Wax+ CA (WCA) reduced significantly green mold and sour rot incidences at different exposure times, with 24 h being the optimal exposure time. The host reactions under infection with different pathogens were similar. During initial exposure, treatment with 5250 mg CA/L wax enhanced significantly the activities of phenylalanine ammonia-lyase (PAL), peroxidase (POD), polyphenol oxidase (PPO), ß-1, 3-glucanase (GLU) and chitinase (CHT) in the presence of direct contact with the pathogen. Simultaneously, WCA induced an increase in total phenolic, flavanone and dihydroflavonol, flavone and flavonol, and lignin contents. Thus, our results suggest that treatment using 5250 mg CA/L wax can be applied early to control diseases by provoking response reactions in citrus fruit.

Effect of applying cinnamaldehyde incorporated in wax on green mould decay in citrus fruits.

BACKGROUND: Green mould caused by Penicillium digitatum is the most damaging postharvest diseases of citrus fruit. Cinnamaldehyde (CA) is a food additive that has potential use in controlling postharvest disease of fruits and vegetables. In this study, the effectiveness of wax with CA (WCA) in controlling Ponkan (Citrus reticulata Blanco) green mould was investigated. RESULTS: The mycelial growth of P. digitatum was inhibited by CA in a dose-dependent manner. The minimum inhibitory concentration and minimum fungicidal concentration (MFC) were both 0.50 mL L-1 . In vivo tests demonstrated that WCA (1 × and 10 × MFC) applied to Ponkan fruits inoculated with P. digitatum could significantly decrease the incidence of green mould for up to 5 days. The WCA treatment increased the activities of catalase, superoxide dismutase, peroxidase, phenylalanine ammonia lyase, polyphenol oxidase, as well as the total phenols and flavonoids contents. Meanwhile, the treatment remarkably decreased the weight loss rate of fruits and maintained fruit quality. These results indicated that WCA treatment might induce defence responses against green mould in citrus fruit. CONCLUSION: Our findings suggest that WCA might be a promising approach in controlling green mould of citrus fruits. © 2017 Society of Chemical Industry.

Antifungal mechanism of sodium dehydroacetate against Geotrichum citri-aurantii.

This study investigated the potential anti-fungal mechanisms of sodium dehydroacetate (SD) against Geotrichum citri-aurantii. The results showed that the cell wall integrity of G. citri-aurantii was not affected, whereas the membrane permeability of G. citri-aurantii mycelia was visibly altered by SD. Dramatic morphological changes of the mycelia, such as loss of cytoplasm, plasmolysis, and dissolution of intracellular substances, were observed by scanning electron microscopy and transmission electron microscopy analyses, indicating that the mycelium is severely damaged by the SD treatment. Furthermore, SD apparently induced a decrease in the intracellular ATP content before 30 min of exposure. An increase in the activity of the Na+/K+-ATPase was also observed, indicating that Na+ ions might enter the cell and thus disturb the energy supply. Taken together, this study's findings suggest that the anti-fungal activity of SD against G. citri-aurantii can be attributed to the disruption of cell membrane permeability and energy metabolism.

Transcriptional profiling analysis of Penicillium digitatum, the causal agent of citrus green mold, unravels an inhibited ergosterol biosynthesis pathway in response to citral.

BACKGROUND: Green mold caused by Penicillium digitatum is the most damaging postharvest diseases of citrus fruit. Previously, we have observed that citral dose-dependently inhibited the mycelial growth of P. digitatum, with the minimum inhibitory concentration (MIC) of 1.78 mg/mL, but the underlying molecular mechanism is barely understood. RESULTS: In this study, the transcriptional profiling of the control and 1/2MIC-citral treated P. digitatum mycelia after 30 min of exposure were analyzed by RNA-Seq. A total of 6355 genes, including 2322 up-regulated and 4033 down-regulated genes, were found to be responsive to citral. These genes were mapped to 155 KEGG pathways, mainly concerning mRNA surveillance, RNA polymerase, RNA transport, aminoacyl-tRNA biosynthesis, ABC transporter, glycolysis/gluconeogenesis, citrate cycle, oxidative phosphorylation, sulfur metabolism, nitrogen metabolism, inositol phosphate metabolism, fatty acid biosynthesis, unsaturated fatty acids biosynthesis, fatty acid metabolism, and steroid biosynthesis. Particularly, citral exposure affected the expression levels of five ergosterol biosynthetic genes (e.g. ERG7, ERG11, ERG6, ERG3 and ERG5), which corresponds well with the GC-MS results, the reduction in ergosterol content, and accumulation of massive lanosterol. In addition, ERG11, the gene responsible for lanosterol 14α-demethylase, was observed to be the key down-regulated gene in response to citral. CONCLUSION: Our present finding suggests that citral could exhibit its antifungal activity against P. digitatum by the down-regulation of ergosterol biosynthesis.

Plasma membrane damage contributes to antifungal activity of citronellal against Penicillium digitatum.

The antifungal activity of citronellal, a typical terpenoid of plant essential oils, against Penicllium digitatum and the possible action mode involved were investigated. Results showed that the mycelial growth and spores' germination of P. digitatum were inhibited by citronellal in a dose-dependent manner. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) were determined to be 1.60 µL/mL and 3.20 µL/mL, respectively. It was found that the plasma membrane of citronellal-treated P. digitatum spores was damaged, as confirmed by the propidium iodide stain results, as well as a higher extracellular conductivity and release of cell constituents in citronellal-treated samples than those of control samples. Moreover, in vivo test results demonstrated that wax + citronellal (WC; 10 × MFC) treatment effectively reduced the incidence of green mold after 5 days of storage at 25 ± 2 °C. These findings suggested that the plasma damage mechanism contributed to the antifungal activity of citronellal against P. digitatum. In addition, citronellal was suggested to be a potential alternative to fungicidal agents in controlling green mold of citrus fruit.

Effect of octanal on the mycelial growth of Penicillium italicum and P. digitatum.

The present study investigated the antifungal activity of octanal against Penicillium italicum and P. digitatum. Results showed that octanal exhibited strong antifungal activity against the test pathogens in a dose-dependent manner. Scanning electron microscopy observation revealed that octanal obviously altered the morphology of P. italicum and P. digitatum hyphae by causing the loss of cytoplasm and distortion of mycelia. A rapid increase in the membrane permeability of P. italicum and P. digitatum was observed after treated with octanal at minimum inhibitory concentration or minimum fungicidal concentration, evidenced by the release of cell constituents, the extracellular conductivity and the extracellular potential of hydrogen. In addition, octanal apparently induced a decrease in total lipid contents of P. italicum and P. digitatum cells. These results suggested that the antifungal activity of octanal against P. italicum and P. digitatum can be attributed to the disruption of the cell membrane integrity and the leakage of cell components.

Integration of covalent organic frameworks and molecularly imprinted polymers for selective extraction of flavonoid naringenin from grapefruit (Citrus × paradisi Macf.) peels.

Grapefruit (Citrus × paradisi Macf.) peel, a by-product of the citrus-processing industry, possesses an important economic value due to the richness of bioactive compounds. In this study, boron-linked covalent organic frameworks integrated with molecularly imprinted polymers (CMIPs) were developed via a facile one-pot bulk polymerization approach for the selective extraction of naringenin from grapefruit peel extract. The obtained CMIPs possessed a three-dimensional network structure with uniform pore size distribution, large surface areas (476 m2/g), and high crystallinity. Benefiting from the hybrid functional monomer APTES-MAA, the acylamino group can coordinate with the boronate ligands of the boroxine-based framework to form B-N bands, facilitating the integration of imprinted cavities with the aromatic skeleton. The composite materials exhibited a high adsorption capacity of 153.65 mg/g, and a short adsorption equilibrium time of 30 min for naringenin, together with favorable selectivity towards other flavonoid analogues. Additionally, the CMIPs captured the template molecules through π-π* interaction and hydrogen bonding, as verified by FT-IR and XPS. Furthermore, they had good performance when employed to enrich naringenin in grapefruit peels extract compared with the common adsorbent materials including AB-8, D101, cationic exchange resin, and active carbon. This research highlights the potential of CMIPs composite materials as a promising alternative adsorbent for naringenin extraction from grapefruit peel.

Inhibitory Mechanisms of trans-2-Hexenal on the Growth of Geotrichum citri-aurantii.

Geotrichum citri-aurantii (G. citri-aurantii) is one of the most important postharvest pathogens leading to a postharvest loss of citrus by causing sour rot. In this study, the antifungal activity of trans-2-hexenal, a natural component of essential oil, against G. citri-aurantii was evaluated. Trans-2-hexenal treatment inhibited the mycelia growth of G. citri-aurantii with a minimum inhibitory concentration and minimum fungicidal concentration of trans-2-hexenal at 0.50 and 1.00 µL/mL, respectively. Moreover, trans-2-hexenal efficiently reduced the incidence of sour rot of Satsuma fruit inoculated with G. citri-aurantii. Ultrastructural observations and Fourier transform infrared (FT-IR) results showed that trans-2-hexenal treatment affected the cell wall and cell membrane instructions of G. citri-aurantii. The content of ß-1,3-glucan was significantly decreased after trans-2-hexenal treatment, but the cell wall permeability was not changed. The decrease in lipid and ergosterol contents might be responsible for this antifungal activity. Several important genes, FKS1, ERG1, ERG7, and ERG11, showed decreasing expression levels after trans-2-hexenal treatment. Molecule-docking results also indicated that trans-2-hexenal could join with the protein of FKS1, ERG1, ERG7, and ERG11 to impact enzyme activities. These results demonstrated that trans-2-hexenal is a promising fungicide for controlling sour rot of harvested citrus fruit by damaging the membrane integrity of G. citri-aurantii.

Carotenoid accumulation in postharvest "Cara Cara" navel orange (Citrus sinensis Osbeck) fruits stored at different temperatures was transcriptionally regulated in a tissue-dependent manner.

UNLABELLED: The main objective of this work was to investigate the effect of storage temperature (4 and 20 °C) on carotenoid accumulation and on the expression levels of seven carotenoid biosynthetic genes (Psy, Pds, Zds, Lcyb, Lcye, Hyb and Zep) in postharvest 'Cara Cara' navel orange (C. sinensis Osbeck) fruits. Storage at 20 °C rapidly increased the carotenoid content in the peel, whereas the content remained unchanged in the pulp before 35 days of storage. By contrast, storage at 4 °C maintained the carotenoid content in the peel before 35 days of storage, after which it slightly increased as time progressed. However, the content in the pulp gradually increased over the entire storage period. In the peel, the gene expressions of Psy and Lcyb were up-regulated at 20 °C but remained unchanged at 4 °C. In addition, the gene expressions of Zds, Hyb, and Zep were repressed at both temperatures before the early storage, followed by a rapid increase only at 20 °C. Then the expressions remained constant level at both temperatures, with the expression level at 20 °C higher than that at 4 °C. Low temperature (4 °C) apparently induced the expression of all the test carotenoid biosynthetic genes in the pulp, in contrast to the nearly stable level at 20 °C. Our present study suggests that the carotenoid biosynthesis in postharvest 'Cara Cara' fruits is transcriptionally regulated, and storage temperature affects the carotenoid accumulation and gene expression in a tissue-dependent manner. KEY MESSAGE: Temperature could affect the carotenoid biosynthesis in postharvest 'Cara Cara' fruits in a tissue-dependent manner. The carotenoid biosynthesis in postharvest 'Cara Cara' fruits was transcriptionally regulated by correlated genes.

γ-Cyclodextrin-Encapsulated Cinnamaldehyde for Citrus Preservation and Its Potential Mechanisms against Penicillium digitatum.

In this study, a γ-cyclodextrin-cinnamaldehyde inclusion compound (γ-CDCL) was prepared to control green mold caused by Penicillium digitatum (P. digitatum) in citrus. The results showed that the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of γ-CDCL against the mycelial growth of P. digitatum were 2.0 g L-1 and 4.0 g L-1, respectively. Simultaneously, eight × MFC γ-CDCL could effectively reduce the incidence of green mold in citrus fruit without impairment of the fruit qualities, meanwhile, eight × MFC γ-CDCL was comparable to Prochloraz in controlling fruit under natural storage conditions. The structure of γ-CDCL was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), and nuclear magnetic resonance (NMR) analyses. Results showed that the successful preparation of γ-CDCL was due to the spatial interaction between H-4,8 of cinnamaldehyde and H-5' of γ-cyclodextrin. Meanwhile, the cell membrane permeability of P. digitatum was impaired by γ-CDCL through massive accumulation of reactive oxygen species, whereas the cell wall integrity was barely affected. These results indicated that γ-CDCL might inhibit the growth of P. digitatum through a membrane damage mechanism and it is a promising alternative to chemical fungicides in controlling the post-harvest citrus decay.

Screening of Oxygenated Aromatic Compounds for Potential Antifungal Activity against Geotrichum citri-aurantii through Structure-Activity Relationship Analysis.

Sour rot caused by Geotrichum citri-aurantii (G. citri-aurantii) is responsible for huge economic losses during citrus fruit storage. However, the availability of chemical fungicides for controlling this disease is rather limited. In the present study, the antifungal activities of 25 oxygenated aromatic compounds against the mycelial growth of G. citri-aurantii were determined, and their corresponding structure-activity relationships were illustrated. Salicylaldehyde (pMIC = 2.689) possessed the strongest inhibitory effect on G. citri-aurantii growth, followed by thymol (pMIC = 2.478) and o-phthalaldehyde (pMIC = 2.429). Molecular electrostatic potential and molecular orbital analysis showed that the antifungal efficiency of test compounds was determined by the number and location of hydroxyl and aldehyde groups and the length of the ester chain. All compounds were selected for quantitative structure-antifungal activity relationship (QSAR) analysis. A three-dimensional-QSAR model of G. citri-aurantii inhibitors was established and demonstrated good predictive capability [comparative molecular field analysis, q2 = 0.532, optimum number of components (ONC) =10, R2 = 0.996, F = 560.325, standard error of estimation (SEE) = 0.034, and two descriptors; comparative similarity index analysis, q2 = 0.675, ONC = 6, R2 = 0.989, F = 263.354, SEE = 0.054, and five descriptors]. QSAR analysis showed that substitution at position 1 with hydrophilic and electron-withdrawing groups produced a hydrogen donor and thus improved the antifungal activity. In contrast, substitution at positions 4 or 5 with hydrophilic and electron-donating groups decreased its antifungal activity. These findings can provide theoretical guidance for preparing effective antifungal drugs for controlling sour rot in citrus.

Exogenous Application of Melatonin to Green Horn Pepper Fruit Reduces Chilling Injury during Postharvest Cold Storage by Regulating Enzymatic Activities in the Antioxidant System.

Chilling injury (CI) caused by exposure to low temperatures is a serious problem in the postharvest cold storage of pepper fruit. Melatonin (MT) has been reported to minimize CI in several plants. To evaluate the effectiveness of MT to minimize CI in green horn pepper and the possible mechanism involved, freshly picked green horn peppers were treated with MT solution at 100 µmol L-1 or water and then stored at 4 °C for 25 d. Results showed that MT treatment reduced CI in green horn pepper fruit, as evidenced by lower CI rate and CI index. MT treatment maintained lower postharvest metabolism rate and higher fruit quality of green horn peppers, as shown by reduced weight loss and respiratory rate, maintened fruit firmness and higher contents of chlorophyll, total phenols, flavonoids, total soluble solids and ATP. Additionally, the contents of hydrogen peroxide, superoxide radical, and malondialdehyde were kept low in the MT-treated fruit, and the activities of the enzymes peroxidase, superoxide dismutase, and catalase were significantly elevated. Similarly, the ascorbate-glutathione cycle was enhanced by elevating the activities of ascorbate peroxidase, glutathione reductase, dehydroascorbate reductase, and monodehydroascorbate reductase, to increase the regeneration of ascorbic acid and glutathione. Our results show that MT treatment protected green horn pepper fruit from CI and maintained high fruit quality during cold storage by triggering the antioxidant system.

Fabrication of γ-cyclodextrin-Based metal-organic frameworks as a carrier of cinnamaldehyde and its application in fresh-cut cantaloupes.

Cinnamaldehyde (CA) is a promising antimicrobial agent for the preservation of fruits and vegetables due to its excellent antibacterial activity. The application is however, limited by its unstable and volatile properties. A biocompatible carbon dots hybrid γ-cyclodextrin-based metal organic framework (CD/MOF) was developed by the seed-mediated method to improve the encapsulation and sustained continuous release of CA. CD/MOF-0.5 exhibited a CA loading efficiency of 28.42% and a sustained release duration time of more than 15 days at 8 oC. The release kinetics results showed that the release behavior of CD/MOF-0.5 fitted well with the Korsmeyer-Peppas release kinetics model, indicating that its sustained release is mainly controlled by diffusion. Both the Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses revealed that CD/MOF-0.5 and CA molecules were linked by hydrogen bonds. Due to the high sustained release performance, CA-loaded CD/MOF-0.5 considerably inhibited the growth of Escherichia coli, hence preventing the spoilage of fresh-cut cantaloupes. CD/MOF-0.5/CA treatment also maintained the qualities of the fresh-cut cantaloupes, prolonging their edibility to five days. This work provides a promising strategy for the prevention of spoilage in food industry.

Isolation and characterization of a Pichia anomala strain: a promising candidate for bioethanol production.

A yeast strain designated as Y-1 was isolated and characterized from wine yeast ("Jiuqu"). Based on the morphological and biochemical results, along with the rDNA internal transcribed spacer region (ITS), Y-1 was identified to be a Pichia anomala strain. Y-1 is an ethanol-tolerant strain, enduring ethanol concentrations of up to 14 %. Y-1 growth medium conditions were optimized, results showing good growth in medium with pH ranges from 3.5-6.5, temperature ranges from 25-30 °C, and inoculums range of 8 %-12 %, while optimum growth conditions were reached at a temperature of 30 °C, pH 5.0, and inoculums of 10 %. Furthermore, when the alkaline hydrolyzed Shatian pummelo peel solutions were inoculated with 10 % Y-1 and fermented at 30 °C for 6 d, 4.7 % pure ethanol (w/w) was produced, as evidenced by gas chromatography analysis. Our present study shows potential for the Y-1 strain to be a promising candidate for bioethanol production.

Antofine inhibits postharvest green mold due to imazalil-resistant Penicillium digitatum strain Pdw03 by triggering oxidative burst.

The emergence of imazalil (IMZ) resistance in Penicillium digitatum has become a great threat for controlling citrus green mold. In this paper, we investigated the antifungal efficiency and mechanism of an alkaloid antofine against an IMZ-resistant P. digitatum strain Pdw03. Results showed that antofine exhibited a strong antifungal activity against the mycelial growth of strain Pdw03, with a minimum inhibitory concentration (MIC) and the minimum fungicidal concentration (MFC) of 1.56 × 10-3 and 1.25 × 10-2  g/L, respectively. In vivo application of antofine effectively delayed the disease progress and reduced the incidence of green mold in citrus fruit. The disease incidence of 10 × MFC antofine-treated fruit after 6 days of storage was only 11% ± 4%, which was significantly lower than that of the control (100% ± 0%). Antofine treatment altered mycelial morphology of strain Pdw03 without affecting the cell wall integrity. Although the ergosterol contents remained stable, a decrease in the total lipid content induced by lipid peroxidation was observed at 30 min of exposure, indicating disruption of cell membrane permeability of strain Pdw03. In addition, the mitochondrial membrane potential (MMP) and adenosine triphosphate (ATP) contents were also decreased at 60 min of exposure. These results indicated that antofine inhibited the growth of strain Pdw03 by disrupting cell membrane permeability and impairing energy metabolism induced by oxidative burst. PRACTICAL APPLICATIONS: One of the most economically important postharvest diseases of citrus fruit is green mold caused by Penicillium digitatum. The pathogen is mainly controlled by using imazalil, but the prolonged and extensive application of this chemical fungicide has led to emergence of numerous IMZ-resistant strains among P. digitatum isolates. Consequently, new and safe strategies for controlling citrus green mold caused by IMZ-resistant P. digitatum strains are urgently needed. In this study, an alkaloid antofine effectively inhibited the growth of IMZ-resistant P. digitatum strain Pdw03 and significantly decreased green mold incidence in the affected citrus fruits. Antofine induced membrane lipid peroxidation of Pdw03 mycelia, resulting in damage to the cell membrane and impairment of energy metabolism. Antofine is therefore a potential antifungal agent for the control of green mold, which provide theoretical guidance for the food industry.