MOF-Based Active Packaging Materials for Extending Post-Harvest Shelf-Life of Fruits and Vegetables.

Active packaging that can extend the shelf-life of fresh fruits and vegetables after picking can assure food quality and avoid food waste. Such packaging can prevent the growth of microbial and bacterial pathogens or delay the production of ethylene, which accelerates the ripening of fruits and vegetables after harvesting. Proposed technologies include packaging that enables the degradation of ethylene, modified atmosphere packaging, and bioactive packaging. Packaging that can efficiently adsorb/desorb ethylene, and thus control its concentration, is particularly promising. However, there are still large challenges around toxicity, low selectivity, and consumer acceptability. Metal-organic framework (MOF) materials are porous, have a specific surface area, and have excellent gas adsorption/desorption performance. They can encapsulate and release ethylene and are thus good candidates for use in ethylene-adjusting packaging. This review focuses on MOF-based active-packaging materials and their applications in post-harvest fruit and vegetable packaging. The fabrication and characterization of MOF-based materials and the ethylene adsorption/desorption mechanism of MOF-based packaging and its role in fruit and vegetable preservation are described. The design of MOF-based packaging and its applications are reviewed. Finally, the potential future uses of MOF-based active materials in fresh food packaging are considered.

Identification of differentially expressed genes associated with aluminum resistance in the soybean plant.

Aluminum (Al) toxicity is a major limitation to crop production in countries where acidic soil is abundant. In China, soybean production is constrained by Al stress-induced toxicity. As such, there is growing interest to develop Al-resistant varieties. In the present study, we sought to determine potential genes, functions and pathways for screening and breeding of Al-resistant varieties of soybean. First, we mined the E-GEOD-18517 dataset and identified 729 differentially expressed genes (DEGs) between untreated and Al-treated groups. Next, we performed Gene Ontology and Kyoto Encyclopedia of Genes and Genome pathways enrichment analysis and observed that most of the screened genes were mainly enriched in defense response, plasma membrane and molecular transducer activity. They were also enriched in three important pathways, the phenylpropanoid biosynthesis, plant-pathogen interaction, and cutin, suberine and wax biosynthesis. Utilizing weighted gene co-expression network analysis of 815 DEGs screened by Venn diagram, we identified DEGs that were the most disparate between treated and untreated groups. LOC100793667 (probable protein phosphatase 2C 60, GLYMA_17G223800), LOC100780576 (ethylene-responsive transcription factor 1B, GLYMA_02G006200), and LOC100785578 (protein ESKIMO 1, GLYMA_02G258000) were the most differentially expressed, which were consistent with the qRT-PCR results. As these genes are known to participate in essential functions, such as cell junction and phenylpropanoid biosynthesis, these genes may be important for breeding Al-resistant varieties. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12298-021-01018-x.

Transcriptome analysis of two soybean cultivars identifies an aluminum respon-sive antioxidant enzyme GmCAT1.

This study investigated the antioxidant defense system involved in the tolerance of soybean (Glycine max) to aluminum (Al) stress. Physiological assays showed that the amount of superoxide free radicals (O2 -), hydrogen peroxide (H2O2), and malondialdehyde (MDA) were significantly lower in an Al-resistant soybean cultivar (cv. PI416937) than in an Al-sensitive soybean cultivar (cv. Huachun18). Comparative analysis of microarray data from both genotypes following Al-stress treatment revealed that the expression of a series of antioxidant enzymes genes was induced in the Al-resistant cultivar. The quantitative real time-PCR (qRT-PCR) assay showed that the transcript levels of genes encoding antioxidant enzymes, including GmCAT1, GmPOD1, GmGST1, GmAPX, GmGSH1, and GmSOD, were higher in the Al-resistant cultivar than in the Al-sensitive cultivar in Al-stress conditions. Furthermore, GmCAT1-overexpressing Arabidopsis plants had improved tolerance to Al-stress and lower O2 -, H2O2, and MDA contents than wild-type plants. Therefore, providing evidence that the antioxidant defense system is essential for Al tolerance in soybean. ABBREVIATIONS: Al: aluminum; O2 -: superoxide free radicals; ROS: reactive oxygen species; H2O2: hydrogen peroxide; MDA: malondialdehyde; qRT-PCR: quantitative reverse transcription polymerase chain reaction; GO: gene ontology; WT: wild type; MS medium: Murashige and Skoog medium.

The effects of hydroxide and epoxide functional groups on the mechanical properties of graphene oxide and its failure mechanism by molecular dynamics simulations.

Graphene oxide (GO) could be assembled via amphiphilic interface adhesion into nano-composites. The deformation behaviors and mechanical properties of the composites are sensitive to the functional species absorbed on GO, which are investigated by molecular dynamics simulations. It is found that the ultimate stress and elastic modulus decreases greatly as the density of function groups absorbed on GO increase from 10% to 50%, but independent on the group type of hydroxide or epoxide ones. Fracture of GO is always initiated and preferentially propagated along the path on which hydroxide or epoxide groups are distributed. Essentially, hydroxide or epoxide groups will weaken the adjacent C-C bonds and induce structure transformation from honeycomb to diamond-like structure as result of hybridization transition from sp2 to sp3. The findings provide us a guidance for the design of GO based composites.

Circular torsion induced fan-blade shaped wrinkling in two-dimensional nano-rings.

Molecular dynamics (MD) simulations are conducted to study the deformation behavior and strain distribution in two-dimensional (2D) nano-rings of graphene, single-layer black phosphorus (SLBP) and single-layer MoS2 (SLMoS2) under circular torsion. Interestingly, fan-blade shaped wrinkling is generated, in which the maximum torsion angle (Δθ) and the potential energy change per atom (ΔPe) increase with increasing inner radius but decrease with increasing temperature. As the inner radius is increased, the wave number of wrinkling increases but the wave amplitude decreases. The geometrical characteristics of wrinkling are closely related to the intrinsic elastic modulus (E) and Poisson's ratio (ν). Specifically, the graphene nano-rings possess the largest Δθ and ΔPe but the smallest wave amplitude, while the SLBP nano-rings exhibit the smallest Δθ and ΔPe but the largest wave amplitude. Furthermore, the strongly anisotropic E and ν values of SLBP result in orientation-dependent geometrical characteristics of wrinkles, and fan-blade shaped wrinkling with a strain vortex is induced, which might substantially enhance the pseudomagnetic fields and optical funnel effect for the separation of photon-induced electron-hole pairs, and thus be exploited to improve the photoelectric properties of 2D materials.