Engineering Corynebacterium glutamicum for de novo production of 2-phenylethanol from lignocellulosic biomass hydrolysate.

BACKGROUND: 2-Phenylethanol is a specific aromatic alcohol with a rose-like smell, which has been widely used in the cosmetic and food industries. At present, 2-phenylethanol is mainly produced by chemical synthesis. The preference of consumers for "natural" products and the demand for environmental-friendly processes have promoted biotechnological processes for 2-phenylethanol production. Yet, high 2-phenylethanol cytotoxicity remains an issue during the bioproduction process. RESULTS: Corynebacterium glutamicum with inherent tolerance to aromatic compounds was modified for the production of 2-phenylethanol from glucose and xylose. The sensitivity of C. glutamicum to 2-phenylethanol toxicity revealed that this host was more tolerant than Escherichia coli. Introduction of a heterologous Ehrlich pathway into the evolved phenylalanine-producing C. glutamicum CALE1 achieved 2-phenylethanol production, while combined expression of the aro10. Encoding 2-ketoisovalerate decarboxylase originating from Saccharomyces cerevisiae and the yahK encoding alcohol dehydrogenase originating from E. coli was shown to be the most efficient. Furthermore, overexpression of key genes (aroGfbr, pheAfbr, aroA, ppsA and tkt) involved in the phenylpyruvate pathway increased 2-phenylethanol titer to 3.23 g/L with a yield of 0.05 g/g glucose. After introducing a xylose assimilation pathway from Xanthomonas campestris and a xylose transporter from E. coli, 3.55 g/L 2-phenylethanol was produced by the engineered strain CGPE15 with a yield of 0.06 g/g xylose, which was 10% higher than that with glucose. This engineered strain CGPE15 also accumulated 3.28 g/L 2-phenylethanol from stalk hydrolysate. CONCLUSIONS: In this study, we established and validated an efficient C. glutamicum strain for the de novo production of 2-phenylethanol from corn stalk hydrolysate. This work supplied a promising route for commodity 2-phenylethanol bioproduction from nonfood lignocellulosic feedstock.

Stabilization and Reinforcement Effect of Fibers on a Bitumen Binder.

This study investigated fibers' stabilization and reinforcement effect on a bitumen binder. The fibers' microstructures were primarily observed using scanning electron microscopy, and laboratory tests, including the oven heating and mesh-basket draindown, were designed and carried out on three different fiber-bitumen binders (lignin, mineral, and carbon fiber) in this paper to evaluate the bitumen adsorption and thermal stability, respectively. Then, the cone sink experiment was performed to check the rheological properties of these fiber-bitumen binders. These results reveal that the stabilization and reinforcement effect increases with the fiber content increasing to the optimal value. The optimal fiber content depends on the performance of the fiber-bitumen binder, and the value found in this paper is 0.4 wt %. The results indicate that the fiber enhances the toughness of the bitumen effectively via its spatial framework, adhesion, and stabilization of the fiber-bitumen binder. The rheological properties and rutting resistance were tested by a dynamic shear rheometer, and the results suggested that the fiber could effectively enhance the flow resistance and the rutting resistance of the fiber-bitumen binder.

Iridoid Glycosides and Flavonoids Isolated from the Twigs and Leaves of Callicarpa nudiflora and Their Anti-Inflammatory Activities.

A new iridoid glycoside, named 6'-O-trans-feruloyl-8-epiloganic acid, together with fifteen known compounds were isolated from the twigs and leaves of Callicarpa nudiflora, a traditional Chinese medicine to treat inflammatory-related diseases. Their structures were identified by comprehensive spectroscopic analysis and comparison with reported data. Bioassay results revealed that twelve of the isolates could obviously inhibit nitric oxide (NO) production in lipopolysaccharide (LPS)-induced RAW 264.7 cell lines with IC50 values from 0.64 to 38.72 µM. Among them, compounds 1 (3.27 µM), 6 (5.23 µM), 13 (1.56 µM) and 14 (0.64 µM) exhibited significantly higher activities than that of the positive control (27.13 µM). Additionally, it was supposed that the presence of the carboxy group at the C-4 position of iridoid glycosides and glycosylation at C-3 position of flavonoids might impact their inhibitory activities against NO production.

Effects of Fiber Type on the Mechanical Properties of the Open-Graded Friction Course Mixture.

The open-graded friction courses (OGFCs) have a large number of interconnected voids, which may cause serious water damage to the pavement. Hence, the road performance needs to be investigated. In this study, the mechanical properties of OGFCs containing two different fibers (lignin and mineral fiber) were investigated. Based on the procedure proposed by the Chinese specification JTG F40-2004, OGFCs were designed with the asphalt content between 4.1 and 4.7 wt % to find the optimal asphalt content (OAC). The mesh-basket draindown test was used to check the fiber's stabilization and absorption of bitumen. OGFCs containing the lignin/mineral fiber with OAC would be preferred in terms of the bulk specific gravity. These results indicate that the fiber can bring higher air voids to the OGFCs, and the different specific gravities of fibers may primarily account for the result. Both the lignin and mineral fibers can bring much more asphalts padded in the pores of mineral aggregates and subsequently larger OAC in OGFCs due to their higher asphalt absorption. Performance experiments were carried out to check the dynamic stability and moisture susceptibility of OGFCs containing the lignin/mineral fiber. The study suggests that the lignin and mineral fiber can be used to adjust the internal environment of OGFCs, enhancing the moisture damage resistance and improving the rutting resistance of OGFCs at high temperatures.

Effect of Fibers on the Performance of a Porous Friction Course.

In this paper, the preparation of a porous friction course (PFC) with styrene-butadiene-styrene (SBS)-modified asphalt and fibers instead of a high-viscosity-modified asphalt was investigated. The aggregate gradation B was chosen to prepare the PFC, and the optimal asphalt content in the PFC containing lignin or basalt fibers was determined to be 4.5% by the Cantabro abrasion experiment and Schellenberg draindown experiment. The freeze-thaw split experiment and immersed Marshall experiment indicated that with the addition of the fiber, the residual stability increased by 7.6 and 2.4% for the PFC with the lignin and basalt fibers, respectively, indicating that fibers can enhance the moisture damage resistance of the PFC. Furthermore, the dynamic stability increased by 17.9 and 6.0% for the PFC with the lignin and basalt fibers, respectively, indicating that fibers can significantly enhance the rutting resistance of the PFC at high temperatures. These results prove that the PFC prepared by SBS-modified asphalt and lignin/basalt fibers reaches the standard of pavement performance.

Characterization of Limonoids Isolated from the Fruits of Melia toosendan and Their Antifeedant Activity against Pieris rapae.

The fruits of Melia toosendan Sieb. et Zucc. (Meliaceae) are a source of bioactive limonoids that can be used as effective pesticides. In this study, two novel limonoids, 6-acetylsendanal and 6-ketocinamodiol, were isolated together with fourteen known compounds, namely four protolimonoids, six trichilin-class limonoids, and four C-seco limonoids. The structures of the new compounds were determined by extensive spectroscopic analyses (HR-ESI-MS, UV, IR, 1D and 2D NMR). The bioassay results revealed that eleven of the extracted limonoids exhibited interesting antifeedant activities against the larvae of Pieris rapae with AFC50 values in the range of 0.11-1.79 mm. Particularly, mesendanin H, with an AFC50 value of 0.11 mm, exhibited a higher activity than the positive control toosendanin. Information on new bioactive limonoids may provide further insight into M. toosendan as a source of bioactive components.