The development of a facile and efficient approach to prepare high-toughness epoxy resin is vital but has remained an enormous challenge. Herein, we have developed a high-performance environment-friendly solid epoxy resin modified with epoxidized hydroxylterminated polybutadiene (EHTPB) via one-step melt blending. The characterization, mechanical performance, curing behavior, and thermal properties of EHTPB-modified epoxy resin were investigated. EHTPB-modified epoxy resin exhibited excellent toughness with a 100% increase in elongation at break of tensile than that of neat epoxy resin. The transfer stress and dissipated energy in the rubber phase were predominant mechanisms of toughening. The toughening effect of EHTPB on solid epoxy resin was better than that of some of the previously reported liquid epoxy resins. Meanwhile, at 10 wt % of EHTPB loading, the EHTPB-modified epoxy resin displayed high strength and 22 and 101% improvement of flexural strength and impact strength, respectively. Moreover, at 10 wt % of EHTPB loading, the activation energy of EHTPB-modified epoxy resin for curing reaction decreased from 73.89 to 65.12 kJÁmol −1 , which is beneficial for the curing reaction. Furthermore, EHTPB-modified epoxy resin had a good thermal stability and the initial degradation temperature increased from 249 to 313 C at 10 wt % of EHTPB loading. This work provides a simple-preparation and highly efficient and large-scale approach for the production of high-toughness environment-friendly solid epoxy resins.
Myriocin, which is produced by Bacillus amyloliquefaciens LZN01, can inhibit the growth of Fusarium oxysporum f. sp. niveum (Fon). In the present study, the antifungal mechanism of myriocin against Fon was investigated with a focus on the effects of myriocin on the cell membrane. Myriocin decreased the membrane fluidity and destroyed the membrane integrity of Fon. Significant microscopic morphological changes, including conidial shrinkage, the appearance of larger vacuoles and inhomogeneity of electron density, were observed in myriocin-treated cells. A membrane-targeted mechanism of action was also supported by transcriptomic and proteomic analyses; a total of 560 common differentially expressed genes (DEGs) and 285 common differentially expressed proteins (DEPs) were identified. The DEGs were further verified by using RT-qPCR. The combined analysis between the transcriptome and proteome revealed that the expression of some membrane-related genes and proteins, mainly those related to sphingolipid metabolism, glycerophospholipid metabolism, steroid biosynthesis, ABC transporters and protein processing in the endoplasmic reticulum, was disordered. Myriocin affected the serine palmitoyl transferase (SPT) activity as evidenced through molecular docking. Our results indicate that myriocin has significant antifungal activity owing to its ability to induce membrane damage in Fon.
Bacillus amyloliquefaciens LZN01 shows antagonistic behaviour against Fusarium oxysporum f. sp. niveum (Fon). This study aimed to analyze the antifungal activity and the functional components of cell-free supernatant from B. amyloliquefaciens LZN01 that inhibited Fon growth. The results showed that the cell-free supernatant (CFS) from the death phase had stronger antifungal activity against Fon compared to those from the exponential stage and stationary phase. The analyses from scanning and transmission electron microscopy demonstrated that treatment with CFS led to cellular morphological changes, including concave formations on the conidial surface, the disruption of cell walls and membranes, the leakage of intracellular contents and the aggregation of organelles. Confocal laser scanning microscopy revealed that the CFS damaged membrane integrity. Myriocin, sphingofungin E, sphingofungin F, 3-methyl-2-oxovaleric acid, gabapentin and sphingofungin C were confirmed as the major differential metabolites by ultrahigh-performance liquid chromatography-LTQ orbitrap (UHPLC-LTQ Orbitrap) MS analysis. Quantitative analysis showed that the myriocin content in the CFS was 0.6 lg/mL, and its minimum inhibitory concentration (MIC) was 1.25 lg/mL. It can be speculated that some antifungal compounds in the CFS, including myriocin, sphingofungin E, sphingofungin F and sphingofungin C, play major roles in inhibiting the growth of Fon and the synergistic effects among these antifungal compounds are important in suppressing Fon reproduction. This study suggests that B. amyloliquefaciens LZN01 is a promising biological agent against Fon as its CFS exerts antifungal activity by deforming conidial structures and damaging membranes and myriocin was one of the major functional components of the CFS.
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