An efficient immobilizing technique of penicillin acylase with combining mesocellular silica foams support and <Emphasis Type="Italic">p</Emphasis>-benzoquinone cross linker

To improve the performance of covalently immobilized penicillin acylase (PA), the immobilization was carried out in mesocellular silica foams (MCFs) using p-benzoquinone as cross linker. The characterizations of the immobilized enzyme were studied carefully. The results showed that the relative activity of the immobilized PA was increased to 145% of that of free enzyme. The activity was 3.7 folds of that of PA on the silica nanoparticles. The enzyme in MCFs presented a turnover equal to that of free enzyme. It was also found that the optimum pH of the immobilized PA shifted to pH 7.5 and the optimum reaction temperature rose from 45 to 50 degrees C. Furthermore, the stability of PA was ameliorated greatly after immobilization. Fourier transform infrared spectroscopy showed no major secondary structural change for PA confined in MCFs. The proposed covalent immobilizing technique would rank among the potential strategies for efficient immobilization of PA.     

Solvent-free synthesis of chiral Schiff-base ligands based on ferrocene under microwave irradiation and application to enantioselective nitroaldol (Henry) reaction

Chiral Schiff-bases 3a-f based on ferrocene were designed and synthesized using solvent-free methods by mixing ferrocene carbaldehyde 1 with amino alcohols and amines 2a-f under microwave irradiation and classical method for the enantioselective nitroaldol (Henry) reaction. The Schiff-bases were obtained in shorter reaction times and improved yield under microwave irradiation method over classical method. The highest enantioselectivity was observed in ligand 3e (95% ee) when CH(2)Cl(2) was used as solvent.     

Selective enzymic esterification of free fatty acids with n-butanol under microwave irradiation and under classical heating

Selective enzymic esterification of free fatty acids, obtained from blackcurrant oil by chemical saponification, with n-butanol using four immobilized lipases under microwave irradiation and under classical heating was studied. A positive effect of microwave irradiation on chemical yields of the products of the enzymic reactions and specificity of lipases were observed in comparison with a controlled heating in an incubator equipped with shaking (classical heating) applied during the identical enzyme-mediated processes. The maximum quantity of -linolenic acid (30%) was obtained with Lipozyme used as biocatalyst of the reaction under microwave irradiation. The maximum quantity of butyl -linolenate (20%) was obtained by a Pseudomonas cepacia lipase catalyzed esterification under classical heating.