Co-immobilization of amine dehydrogenase and glucose dehydrogenase for the biosynthesis of (S)-2-aminobutan-1-ol in continuous flow.

Reductive amination by amine dehydrogenases is a green and sustainable process that produces only water as the by-product. In this study, a continuous flow process was designed utilizing a packed bed reactor filled with co-immobilized amine dehydrogenase wh84 and glucose dehydrogenase for the highly efficient biocatalytic synthesis of chiral amino alcohols. The immobilized amine dehydrogenase wh84 exhibited better thermo-, pH and solvent stability with high activity recovery. (S)-2-aminobutan-1-ol was produced in up to 99% conversion and 99% ee in the continuous flow processes, and the space-time yields were up to 124.5 g L-1 d-1. The continuous reactions were also extended to 48 h affording up to 91.8% average conversions. This study showcased the important potential to sustainable production of chiral amino alcohols in continuous flow processes.

Effect of initial support particle size of MnO x /TiO2 catalysts in the selective catalytic reduction of NO with NH3.

A series of manganese-based catalysts supported by 5-10 nm, 10-25 nm, 40 nm and 60 nm anatase TiO2 particles was synthesized via an impregnation method to investigate the effect of the initial support particle size on the selective catalytic reduction (SCR) of NO with NH3. All catalysts were characterized by transmission electron microscopy (TEM), N2 physisorption/desorption, X-ray diffraction (XRD), temperature programmed techniques, X-ray photoelectron spectroscopy (XPS) and in situ diffuse reflectance infrared transform spectroscopy (DRIFTS). TEM results indicated that the particle sizes of the MnO x /TiO2 catalysts were similar after the calcination process, although the initial TiO2 support particle sizes were different. However, the initial TiO2 support particle sizes were found to have a significant influence on the SCR catalytic performance. XPS and NH3-TPD results of the MnO x /TiO2 catalysts illustrated that the surface Mn4+/Mn molar ratio and acid amount could be influenced by the initial TiO2 support particle sizes. The order of surface Mn4+/Mn molar ratio and acid amount over the MnO x /TiO2 catalysts was as follows: MnO x /TiO2(10-25) > MnO x /TiO2(40) > MnO x /TiO2(60) > MnO x /TiO2(5-10), which agreed well with the order of SCR performance. In situ DRIFTS results revealed that the NH3-SCR reactions over MnO x /TiO2 at low temperature occurred via a Langmuir-Hinshelwood mechanism. More importantly, it was found that the bridge and bidentate nitrates were the main active substances for the low-temperature SCR reaction, and bridge nitrate adsorbed on Mn4+ showed superior SCR activity among all the adsorbed NO x species. The variation of the initial TiO2 support particle size over MnO x /TiO2 could change the surface Mn4+/Mn molar ratio, which could influence the adsorption of NO x species, thus bringing about the diversity of the SCR catalytic performance.

Anti-tumor activity of the regenerated triple-helical polysaccharide from Dictyophora indusiata.

A triple helical polysaccharide (PD3) was isolated from Dictyophora indusiata. After denaturation in dilute NaOH solution (0.3 M) and renaturation by sequential dialysis, regenerated polysaccharide (RPD3) was obtained. The physico-chemical properties of RPD3 including intrinsic viscosity [η], molecular weight (Mw) and optical rotation were similar to those of PD3, which suggested that RPD3 also had a triple helical structure after denaturation-renaturation. However, different intrinsic viscosity dependence on the concentration of NaOH solution was noted in PD3 and RPD3, which indicated that RPD3 had lower chain tightness compared with PD3. The anti-tumor activity of this polysaccharide after denaturation-renaturation treatment was further investigated. Both PD3 and RPD3 showed no direct cytotoxicity against S-180 cells in vitro but behaved anti-tumor activity in vivo. Meanwhile, RPD3 in high-dose group showed much higher anti-tumor activity than that of PD3, suggesting that the denaturation-renaturation treatment improved the bioactivity of the polysaccharide from D. indusiata.

High quality gold nanorods and nanospheres for surface-enhanced Raman scattering detection of 2,4-dichlorophenoxyacetic acid.

Nearly monodisperse Au nanorods (NRs) with different aspect ratios were separated from home-synthesized polydisperse samples using a gradient centrifugation method. The morphology, size and its distribution, and photo-absorption property were analyzed by transmission electron microscopy, atomic force microscopy and UV-visible spectroscopy. Subsequently, using colloidal Au NRs (36.2 nm ×10.7 nm) with 97.4% yield after centrifugation and Au nanospheres (NSs) (22.9 ± 1.0 nm in diameter) with 97.6% yield as Au substrates, surface-enhanced Raman scattering (SERS) spectra of 2,4-dichlorophenoxyacetic acid (2,4-D) were recorded using laser excitation at 632.8 nm. Results show that surface enhancement factors (EF) for Au NRs and NSs are 6.2 × 10(5) and 5.7 × 10(4) using 1.0 × 10(-6) M 2,4-D, respectively, illustrating that EF value is a factor of ~10 greater for Au NRs substrates than for Au NSs substrates. As a result, large EF are a mainly result of chemical enhancement mechanisms. Thus, it is expected that Au NPs can find a comprehensive SERS application in the trace detection of pesticide residues.

Chemical analysis and antioxidant activity in vitro of a ß-D-glucan isolated from Dictyophora indusiata.

In this study, a water-soluble polysaccharide (PPS) from Dictyophora indusiata was purified and investigated through a combination of gel chromatography (Sephadex G-200), infrared (IR) spectroscopy, and gas chromatography-mass spectrometry (GC-MS). The results indicated that PPS has a backbone of ß-conformation, mainly consist of glucose (98.58%). And the antioxidant activities of PPS were investigated in vitro including reducing power, hydroxyl assay, superoxide radical assay and DPPH scavenge activity. The results showed that PPS has antioxidant activities in all these assay systems, suggesting it may be explored as a novel natural antioxidant with potential therapeutic properties in mammalian systems.