基于界面活化的脂肪酶固定化方法研究进展

界面活化作用可以显著提高脂肪酶的催化活性,对脂肪酶在所有领域的应用均有重要影响。因此,在脂肪酶固定化方法的设计过程中,应该要考虑到界面活化作用的重要性。本文综述了国内外基于界面活化的脂肪酶固定化方法研究进展,并结合绿色高效型生物催化剂的发展要求对新型脂肪酶固定化方法的研究方向及发展前景提出了展望。

Facile preparation of nanocrystal-assembled hierarchical mordenite zeolites with remarkable catalytic performance

The present study reports a novel strategy to fabricate nanocrystal-assembled hierarchical MOR zeolites. This is the first demonstration of hierarchical MOR without preferential growth along the c-axis, which facilitates mass transfer in the 12-membered ring channels of MOR zeolite for the conversions involving bulky molecules. The facile method involves the combined use of tetraethylammonium hydroxide （TEAOH） and commercial surfactants, in which TEAOH is essential for the construction of nanocrystal assemblies. The surfactant serves as a crystal growth-inhibiting agent to further inhibit nanocrystalline particle growth, resulting in enhanced mesoporosity. The hierarchical MOR assembled particles, constructed of 20-50-nm crystallites, exhibit superior catalytic properties in the alkylation of benzene with benzyl alcohol compared with the control sample, as the hierarchical MOR possesses a larger external surface area and longer c-axis dimension. More importantly, the material shows improved activity and stability in the dimethyl ether carbonylation to methyl acetate reaction, which is a novel route to produce ethanol from syngas.

Synthesis and Surface Activity of Heterogemini Imidazolium Surfactants

A series of heterogemini imidazolium surfactants with two-methylene spacer groups （[Cm- 2-Cnim]Br2, m, n=8, 10, 12, 14, 16; m≠n） have been synthesized and characterized by 1H NMR and ESI-MS spectroscopy. The effects of various reaction parameters, including stoichiometry, reaction temperature and time, were investigated. In addition, the surface activity study about heterogemini imidazolium surfactants was carried out and the influences of dissymmetric degree on the surface properties were also discussed.

Preparation of Surfactant-Free Pt and PtRu Nanoparticles with High Activity for Methanol Oxidation

A simple and green approach to synthesize highly active electro-catalysts for methanol oxi- dation reaction （MOR） without using any organic agents is described. Pt nanoparticles are directly deposited on the pre-cleaned and pre-oxidized multiwall carbon nanotubes （MWC- NTs） from Pt salt by using CO as the reductant. MOR activity has been characterized by both cyclic voltammetry and chronoamperometry, the current density and mass specific current at the peak potential （ca. 0.9 V vs. RHE） reaches 11.6 mA/cm^2 and 860 mA/mgpt, respectively. After electro-deposition of Ru onto the Pt/MWCNTs surface, the catalysts show steady state mass specific current of 20 and 80 mA/mgpt at 0.5 and 0.6 V, respectively.

Effects of Preparation Parameters on Paraffin Wax Microemulsion

The paraffin wax microemulsion was prepared from fully refined paraffin wax No.58-60 in the presence of a nonionic surfactant and an anionic surfactant.The influence of manufacturing parameters on the particle diameter of paraffin wax microemulsion included the quantity of the emulsifier,the temperature and emulsification time,the stirring speed,the pH value and the auxiliary ingredient(cosurfactant).The test results showed that the temperature of emulsification had little effect on the particle size of paraffin wax microemulsion in a temperature range of 75-85 ℃.Other manufacturing parameters all had a great effect on the particle size of paraffin wax microemulsion.The optimum preparation conditions included:a w(emulsifier) of 6%,an emulsification temperature of 80 ℃,an emulsification time of 40 min,a pH value of about 8,and a stirring speed of 600 r/min,with n-amyl alcohol serving as the co-surfactant.Under these conditions,a translucent and baby blue paraffin wax emulsion was prepared with its particle size equating to 97 nm.

Technological Properties of Yeast Produced Surface Active Compounds in Connection with Their Application in Clean-Up Technologies

Biologically produced surfactants （SACs） can mobilize and solubilize non-aqueous phase liquids （NAPL） adsorbed onto soil constituents. The interest in microbial surfactants has increased during recent years due to their lower toxicity, higher biodegradability, selectivity and specific activity under extreme conditions than synthetic SACs. Main output of the project represents preparation of this yeast biosurfactant intended for washing of matrices contaminated by NAPL. The influence of cultivation media composition on biosurfactant production was studied and basic properties （critical micelle concentration （CMC）, minimum surface tension） of isolated biosurfactants were compared with properties of synthetic surfactant with surface tension measurement. The interracial tension of the systems containing aqueous solutions of different concentrations and non-polar substances was measured with petroleum compounds （kerosene Jet A-l）, aromatic and aliphatic hydrocarbons （represented by toluene and hexane）. The solution of biosurfactant Yarrowia lipolytica （YAR） in the concentration range of 0-500 mg/L reduced interracial tension by 80% in all representative systems with model contaminants; biosurfactant Candida bombicola （CAN） was less efficient. Solubilization properties were proved with toluene and hexachlorocyclohexane （HCH） isomers alpha and gamma, and effective concentration of biosurfactants was determined as 100 mg/L for toluene and HCH. SACs produced by lipophilic yeast with non-toxic and non-pathogenic status （Yarrowia lipolytica, Candida sp., etc.） seem to be very promising. The results obtained will be used for the application of biosurfactants in the clean-up technologies as agents for the mobilization of non-polar contaminants as well as for stimulation of bioremediation processes.

Influence of surfactants on the morphology and photocatalytic activity of Bi_2WO_6 by hydrothermal synthesis

The flower-like microsphere Bi2WO6 with an average diameter of 2.5 μm is synthesized by a simple hydrothermal method in the presence of surfactant sodium dodecyl sulfate （SDS） or polyvinylpyrrolidone （PVP）. The crystalline phase, compositions, morphology, microstructure, surface area and band gap energy of the Bi2WO6 are characterized by X-ray diffraction, X-ray energy-dispersive spectrum, scanning electron microscopy, transmission electron microscopy and absorption spectra. It is found that surfactant has a significant influence on the microstructure and properties of the samples. The surfaetant SDS en- hances the surface area and photocatalytic activity of Bi2WO6, while the surfactant PVP has an opposite effect. Under Xe lamp irradiation, the Bi2WO6 sample prepared in the presence of SDS can degrade dye Rhodamine B （RhB） effectively.