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Enantioselective Hydrolysis (enantioselective + hydrolysis)
Selected AbstractsChemInform Abstract: Enzyme-Mediated Enantioselective Hydrolysis of Cyclic Carbonates Bearing an Unsaturated Substituent.CHEMINFORM, Issue 49 2002Kazutsugu Matsumoto Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Enzymatic Production of l -Menthol by a High Substrate Concentration Tolerable Esterase from Newly Isolated Bacillus subtilis ECU0554ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 3 2009Gao-Wei Zheng Abstract Enzymatic preparation of l -menthol has been attracting much attention in the flavor and fragrance industry. A new ideal strain, Bacillus subtilis ECU0554, which exhibited high hydrolytic activity and excellent enantioselectivity towards l -menthyl ester, has been successfully isolated from soil samples through enrichment culture and identified as Bacillus subtilis by 16S rDNA gene sequencing. The esterase extracted from B. subtilis ECU0554 (BSE) showed the best catalytic properties (E>200) for dl -menthyl acetate among the five menthyl esters examined. Enantioselective hydrolysis of 100,mM dl -menthyl acetate at 30°C and pH,7.0, using crude BSE as biocatalyst and 10% ethanol (v/v) as cosolvent, resulted in 49.0% conversion (3,h) and 98.0% ee for the l -menthol produced, which were much better than those using commercial enzymes tested. Moreover, BSE exhibited strong tolerance against high substrate concentration (up to 500,mM), and the concentration of l -menthol produced could reach as high as 182,mM, and more importantly, the optical purity of l -menthol produced was kept above 97% ee, which were not found in previous reports. These results imply that BSE is a potentially promising biocatalyst for the large-scale enzymatic preparation of l -menthol. Using this excellent biocatalyst, the enzymatic production of l -menthol will become a mild, efficient, inexpensive and easy-to-use "green chemistry" methodology. [source] Newly isolated Streptomyces spp. as enantioselective biocatalysts: hydrolysis of 1,2-O-isopropylidene glycerol racemic estersJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2005F. Molinari Abstract Aims:, To identify microbial strains with esterase activity able to enantioselectively hydrolyse esters of (R,S)-1,2-O-isopropylidene glycerol. Methods and Results:, The microbial hydrolysis of various racemic esters of 1,2-O-isopropylidene glycerol (IPG) was attempted by screening among Streptomyces spp. previously selected on the basis of their carboxylesterase activity. The best results were observed in the hydrolysis of butyrate ester and two strains appeared promising as they showed opposite enantioselectivity: Streptomyces sp. 90852 gave predominantly (S)-IPG, while strain 90930 mostly gave the R -alcohol. Streptomyces sp. 90930 was identified as Streptomyces violaceusniger, whereas Streptomyces sp. 90852 is a new species belonging to the Streptomyces violaceus taxon. The carboxylesterase belonging to strain 90852 gave a maximum value of enantiomeric ratio (E) of 14,16. This strain was lyophilized and used as dry mycelium for catalysing the synthesis of isopropylidene glycerol butyrate in heptane showing reaction rate and enantioselectivity (E = 6·6) lower than what observed for the hydrolysis. Conclusions:, A new esterase with enantioselective activity towards (R,S)-IPG butyrate has been selected. The best enantioselectivity is similar or even better than the highest reported value in the literature with commercial enzymes. The enzyme is produced by a new species belonging to the S. violaceus taxon. Significance and Impact of the Study:, New esterases from streptomycetes can be employed for the enantioselective hydrolysis of chiral esters derived from primary alcohols, not efficiently resolved with commercial enzymes. [source] Production and Characteristics of an Enantioselective Lipase from Burkholderia sp.CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 2 2008GXU5 Abstract The lipase production of Burkholderia sp. GXU56 was influenced by carbon and nitrogen sources, inorganic salts, initial pH of the medium and cultivation temperature. The maximum lipase production was 580.52,U/mL and reached 5,times the level of the basic medium in the optimum medium at pH 8.0, 32,°C, 200,rpm and 40,48,h. The lipase was purified 53.6,fold to homogeneity and the molecular weight was 35,KDa on SDS-PAGE. The optimum pH and temperature of the lipase were 8.0 and 40,°C, respectively, and it was stable in the range of pH 7,8.5 and at temperatures below 45,°C. The lipase activity was strongly inhibited by Zn2+, Cu2+, Co2+, Fe2+, Fe3+ ions and SDS, while it was stimulated by Li+ and Ca2+ ions and in presence of 0.1,% CTAB, 0.1,% Triton X-100 and 10,% DMSO. Km and Vmax of the lipase were calculated to be 0.038,mmol/L, and 0.029,mmol/L min,1, respectively, with PNPB as the substrate. The GXU56 lipase showed enantioselective hydrolysis of (R,S)-methyl mandelate to (R)-mandelic acid, which is an important intermediate in the pharmaceutical industry. [source] | ||||||||||