Lactic acid bacteria (LAB) starter cultures can be processed by many drying techniques, among which spray drying has great potential. However, injuries of LAB during spray drying lead to a low survival rate. The microbial injuries of LAB during spray drying are specifically induced by dehydration inactivation, thermal inactivation, and balance between the two. To reduce the drying temperature, new drying techniques based on spray drying were tried; that is, low-temperature vacuum–spray drying and spray–freeze drying. 相似文献
An ordered mesoporous LTA zeolites (MLTA) have been synthesized in presence of the bridged polysilsesquioxane monomer (BS-1) as mesoporogen. The relatively well-defined small-angle X-ray diffraction peaks and nitrogen sorption isotherms with narrow pore size distribution centered at around 2.2 nm both indicated the presence of uniformly mesopores in MLTA samples. The scanning electron microscopy and transmission electron microscopy observations further confirmed that the uniform and partially interconnected intracrystal mesopores were randomly distributed throughout the globular particles with rugged surfaces. Interestingly, removal of the BS-1 resulted in uniform mesopore diameters that are nearly consistent with the molecular size of BS-1 (1.8 nm). 29Si MAS NMR revealed that the BS-1 was linked to MLTA zeolite crystal surface through 2 Si–O bonds and 3 Si–O bonds before calcinations. Nitrogen sorption analysis showed that the mesoporosity in MLTA samples could be adjusted by adding different amounts of BS-1 in starting gels. Relative to conventional mesoporous materials, one obvious feature of MLTA is that the resultant mesopores were structured by the bridged polysilsesquioxane monomer instead of commercial polymers or micelles, which broad the routes in synthesizing of various mesoporous materials with controllable pore size distribution, adjustable mesopore volume, and large surface area. 相似文献
The effects of five layered double hydroxides (LDHs) with different zinc ratio on the physical and rheological properties, chemical components, and anti-UV aging performance of asphalt were evaluated. Results show that LDHs improve the deformation resistance of asphalt at high temperature. After UV aging, LDH-modified asphalts show the smaller changes of physical and rheological properties and chemical components in comparison with asphalt, indicating the improved UV aging resistance. By comparison, the LDHs with higher ratio of zinc in the layers have the more outstanding UV reflection ability, leading to a beneficial effect in improving UV aging resistance of asphalt. 相似文献
This study focuses on the effects of the tetrahydrofuran-soluble fraction of direct coal liquefaction residue as a modifier to modify asphalt with formaldehyde. The properties and carbonization behavior of matrix asphalt and the modified asphalts were studied. The results indicate that the ductility properties of modified asphalts have been effectively improved. The morphology of modified asphalts without the addition of formaldehyde is a set of uniform distribution point, and it is converted from linear distribution to clustered distribution observed in fluorescence microscope images with the increase of the adding amount of formaldehyde. 相似文献
Dynamic reductive kinetic resolutions of racemic 3‐arylalkanones have been performed by the proper combination of an alcohol dehydrogenase and a basic anionic resin. The best results were found for the bioreduction with the alcohol dehydrogenase type A from Rhodococcus ruber DSM 44541 overexpressed in Escherichia coli (E. coli/ADH‐A) and the commercially available evo‐1.1.200, while the Amberlite IRA‐440 C and the DOWEX‐MWA‐1 resins allowed efficient in situ racemizations. Reaction conditions were optimized in terms of enzyme source and loading, type and amount of resin, pH, temperature and reaction times, obtaining a series of (R,R)‐substituted propan‐2‐ols with good conversions and both diastereoselectivity and stereoselectivity. As a proof of concept, the subsequent intramolecular cyclization of a selected propan‐2‐ol substrate afforded a valuable isochroman heterocycle without any loss of the optical purity.
Copper‐catalyzed aerobic coupling of thiols and alcohols affords sulfinates and thiosulfonates. These products are assumed to form via sulfinyl radicals which are not commonly found in oxidative coupling reactions of thiols. A reaction mechanism involving sulfinyl radicals is proposed, and mass and electron paramagnetic resonance (EPR) experimental results are provided.
The palladium‐catalyzed ketone‐directed dual sp2 C H activation and sp3 C H functionalization has been applied for fullerene functionalization for the first time. The sec‐alkyl aryl ketones have been exploited to react with [60]fullerene (C60) to provide the novel and scarce C60‐fused tetralones. The combined use of a highly active cationic palladium(II) catalyst and trifluoromethanesulfonic acid is crucial for the improvement of the reaction yield. A plausible reaction mechanism leading to the observed products has been proposed, and the electrochemistry of the fullerene products has also been investigated.
A metal‐free aerobic autoxidative nitrooxylation of alkenyl oximes mediated by tert‐butyl nitrite is described. Molecular oxygen is used as the oxidizing reagent, avoiding use of organic trapping reagents such as 2,2,6,6‐tetramethylpiperidine 1‐oxyl (TEMPO). The desired products were obtained in generally high yields.
An intramolecular palladium(II)‐catalyzed dearomative arylation reaction of indoles via C H bond functionalization was developed, providing access to structurally novel spiroindolenines with moderate to good yields. A one‐pot process for the synthesis of spiroindoline derivatives was also realized.
