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The purpose of this research is to solve the problem of debonding of polyacrylonitrile (PAN) fibers in asphalt to improve the property of asphalt materials. A simple layer-by-layer self-assembly method was employed, in which a chitosan (CS)/phytanic acid (PA) coating was first constructed on the fiber surface. This coating immobilized Fe3O4 nanoparticles on the fiber surface by electrostatic adsorption and coordination, resulting in a robust active surface to obtain Fe3O4-PA-CS-PAN fibers, which were used to laminate styrene–butadiene–styrene (SBS)-modified asphalt. Dynamic shear rheometer (DSR) tests confirmed that the Fe3O4-PA-CS-PAN fiber-modified asphalt possessed superior viscoelastic properties and rutting resistance. At 64 °C, the viscosity modulus (G′) and viscous modulus (G′′) of the 1.5% Fe3O4-PA-CS-PAN fiber-modified asphalt increased by 18.23% and 26.19%, respectively, compared with that of the same dosage of PAN fiber-modified asphalt. This can be ascribed to the effective enhancement of the bonding of the interface between the modified PAN fibers and the asphalt. This research contributes to the development and improvement of future road materials. [ABSTRACT FROM AUTHOR]

As an important five-carbon platform chemical to synthesize polyesters and polyamides, glutaric acid is widely used in numerous biochemical fields such as consumer goods, textile, and footwear industries. However, the application of glutaric acid is limited by the low yield of its bio-production. In this study, a metabolically engineered Escherichia coli LQ-1 based on 5-aminovalerate (AMV) pathway was used for glutaric acid fed-batch fermentation. Given the significance of nitrogen source in the bio-production of glutaric acid by AMV pathway, a novel nitrogen source feeding strategy feedbacked by real-time physiological parameters was proposed after evaluating the effects of nitrogen source feeding (such as ammonia and ammonium sulfate) on glutaric acid bio-production. Under the proposed nitrogen source feeding strategy, a significantly improved glutaric acid production of 53.7 g L–1 was achieved in a 30 L fed-batch fermentation by the metabolically engineered E. coli LQ-1, which was an improvement of 52.1% over pre-optimization. Additionally, a higher conversion rate of 0.64 mol mol–1 (glutaric acid/glucose) was obtained compared with the previously reported bio-production of glutaric acid with E. coli. These results indicated that the nitrogen source feeding strategy proposed in this study will be useful for achieving the efficient and sustainable bio-based production of glutaric acid. [ABSTRACT FROM AUTHOR]

Degumming is the vital and critical step in the preparation of hemp fiber for textile application. However, the traditional chemical degumming processes use large amounts of harmful chemicals, especially strong alkalis, which have caused severe challenges to the environment. The reaction conditions of alkaline pectinase and alkaline pectinase were studied in this research, and the alkaline pectinase-xylanase system was successfully applied to the degumming of hemp fibers in mild conditions (T = 55 °Cand pH = 8.0) without strong alkali. A comparative analysis of hemp fibers treated under different conditions showed that the alkaline pectinase-xylanase system degummed up to about 50% gum removal within 5.5 h, making the fibers smoother and stronger. After alkaline pectinase-xylanase system treatment (0.6 g pectinase, 0.3 g xylanase, 55 °C, pH 8.0, 5.5 h), the removal ratio of pectin and hemicellulose reached 75% and 40%, respectively. And linear density and tenacity of the fiber were 17.4 dtex and 5.62 cN/dtex, respectively. SEM, FT-IR and XRD analysis furthermore demonstrated the excellent effects of the proposed process. The degumming fiber had better water retention performance (513%) and moisture sorption (8.9%), which has more excellent application prospects in the textile industry. Moreover, the method abandons the use of acid and alkali and can provide an eco-friendly degumming process for hemp fiber. [ABSTRACT FROM AUTHOR]

To optimize the rheological properties of warm-mix asphalt and analyze its ultraviolet (UV) aging behaviors, organic montmorillonite was selected to modify the Sasobit warm-mix asphalt. 3% Sasobit was added into the hot mix asphalt to prepare warm-mix asphalt; and then, three different contents of organic montmorillonite (1%, 2%, and 3%) were added to modify the warm-mix asphalt compositely. Subsequently, the road performance and UV aging behaviors of prepared asphalt were evaluated by some rheological indicators; and then, the modification mechanism was investigated by micro testing methods, including Fourier transform infrared spectroscopy (FTIR) test and Fluorescent microscope (FM) test. Results show that with the introduction of Sasobit, construction workability and high-temperature properties of hot mix asphalt were improved, while its fatigue performance and low-temperature properties were decreased. Fortunately, adding organic montmorillonite into the prepared warm-mix asphalt can significantly optimize its fatigue performance while having little influence on its low-temperature properties. UV aging test results show that DSRFn is the most sensitive indicator to characterize the UV aging behaviors of asphalt. Meanwhile, DSRFn aging indexes of warm-mix asphalt and those with 1%–3% organic montmorillonite were reduced by 28.88%, 46.41%, 48.55%, and 46.15%, respectively, compared with that of hot mix asphalt, indicating that Sasobit warm-mix asphalt has superior aging resistance than hot mix asphalt and that the addition of organic montmorillonite can further improve this ability. Microscope test results confirm that the intercalated structure or exfoliated structure may be formed in the asphalt binders, thereby enhancing the rheological properties. In accordance with the presented results, it is recommended that the optimum content of montmorillonite is 2%, which can promote the prepared asphalt samples to obtain excellent rheological properties. [ABSTRACT FROM AUTHOR]

To improve the performance of desulfurized rubber modified asphalt (DRMA), especially its high‐temperature performance, three modifiers (including polyphosphoric acid [PPA], styrene‐butadiene‐styrene [SBS], and rock asphalt) were selected to modify DRMA respectively. The conventional performance, rheological properties, chemical composition, and thermal decomposition were characterized to analyze the performance and modification mechanism of DRMA and its composites. Test results show that, the addition of PPA, SBS, and rock asphalt can all improve the high temperature of DRMA, among which the desulfurized rubber/rock asphalt compound modified asphalt (DRMA‐ROCK) has the best high‐temperature performance; however, its construction workability, storage stability, and low‐temperature performance are poor. In contrast, desulfurized rubber/PPA compound modified asphalt (DRMA‐PPA) not only has better high‐temperature performance, but also has excellent low‐temperature performance, storage stability, and fatigue performance. Fourier infrared spectroscopy (FTIR) test confirms that the modification process of DRMA by these modifiers is chemical modification, and the characteristic peak indexes obtained from FTIR also prove that DRMA‐ROCK has better high‐temperature performance but poor construction workability from the microscopic point of view. Furthermore, thermogravimetric analysis‐differential scanning calorimetry test shows that the addition of rock asphalt improves the thermal stability of DRMA, while PPA and SBS decrease its thermal stability. From the above results, it can be concluded that DRMA‐PPA has excellent comprehensive properties. [ABSTRACT FROM AUTHOR]

Cadaverine has the potential to become an important platform chemical for the production of nylon. Previously, a system that overexpresses the Klebsiella oxytoca lysine decarboxylase in Escherichia coli was engineered. The system was optimized by codon optimization, and tuning the expression level of the gene by testing various promoters and inducer concentrations. Here, we further improved the system by optimizing the sequence located in the region of the ribosome-binding site in order to enhance translation efficiency. We also identified mutant lysine decarboxylase enzymes that demonstrated enhanced cadaverine-production ability. Together, these modifications increased cadaverine production in the system by 50%, and the system has a yield of 80% from lysine-HCl under the conditions we tested. This is the first time that a system to produce cadaverine using the lysine decarboxylase from K. oxytoca performed at a level that is competitive with the traditional systems using the E. coli lysine decarboxylases in both lab-scale and batch fermentation conditions. [ABSTRACT FROM AUTHOR]

Cadaverine, as a biogenic amine, is an important platform chemical for the production of industrial polymers, such as polyamides, polyurethanes, and nylon. Previous efforts focused on the bio-based production of cadaverine using two lysine decarboxylases of Escherichia coli CadA and LdcC. In this study, we report the biotransformation of cadaverine using a lysine decarboxylase from Klebsiella oxytoca. Codon optimization of the gene encoding this enzyme was carried on for the heterologous expression in E. coli, which led to a system that converted more than 24% lysine-HCl to cadaverine compared to the same system expressing CadA. The system was further optimized by using three different inducible promoters to control the expression of lysine decarboxylase gene of K. oxytoca in E. coli. The final optimized system converted lysine-HCl to cadaverine at a conversion rate of 0.133%/min/g. When the optimized system described above is coupled to an industrial process, the combined process has the potential to produce cadaverine with high conversion efficiency (46%) from sugar. [ABSTRACT FROM AUTHOR]