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Vernonia galamensis is an annual herb whose seed oil contains high levels of an epoxy fatty acid, vernolic (cis-12,13-epoxy cis-9-octadecenoic) acid. The seed also contains lipase activity in the dormant state. A lipase was purified from the seed and its substrate specificity studied in isooctane. The lipase shows pronounced selectivity for the native triacylglycerol, trivernolin. The rate of hydr
Drinking water is delivered from the treatment plant to the consumer through kilometres of pipes. Lining these pipes are communities of bacteria living as biofilms. Little is known about the microbial ecology of these biofilms, as access to drinking water pipes for sampling is often limited to pipes sporadically removed for repair or replacement. Bacteria are constantly exchanged between the biofi
Lipases were investigated with respect to their ability to catalyse the incorporation of fatty acids into phosphatidylcholine (PC) by interesterification reactions. The enzymes were dried onto solid support materials and the conversions were carried out in water-saturated toluene. Three lipases (two fungal and one plant enzyme) had the desired activity; immobilized lipase from Mucor miehei (Lipozy
Purified hydroxynitrile lyase (HNL) from Manihot esculenta was crystallized by the sitting-drop vapour-diffusion method. The bipyramidal crystals formed (10-20 μm) were cross-linked with different amounts of glutaraldehyde and used as biocatalyst for the synthesis of optically active cyanohydrins. The cross-linked crystals were more stable than Celite-immobilized enzymes when incubated in organic
Enzymatic transglycosylation of lactose into oligosaccharides was studied using wild-type β-glucosidase (CelB) and active site mutants thereof (M424K, F426Y, M424K/F426Y) and wild-type β-mannosidase (BmnA) of the hyperthermophilic Pyrococcus furiosus. The effects of the mutations on kinetics, enzyme activity, and substrate specificity were determined. The oligosaccharide synthesis was carried out
A model was developed which describes simultaneous reaction and internal diffusion for kinetically controlled, immobilized α-chymotrypsin-catalyzed, oligopeptide synthesis in acetonitrile medium. The model combines the equations that describe the intrinsic kinetics of four different reactions and the physical characteristics of three different support materials, as determined experimentally, to pr
The transglucosylation reaction catalyzed by wild-type β-glucosidase CelB from hyperthermophilic Pyrococcus furiosus and active site mutants (M424K, F426Y, M424K/F426Y) was studied. The conversion of pentyl-β-glucoside to hexyl-β-glucoside in hexanol was used as a model transglucosylation reaction. Hydrolysis to glucose was a side reaction. The activity (rates of hydrolysis and transglucosylation)
The maximal production of galactooligosaccharides (GOS) from lactose by (β-glycosidases from the hyperthermophilic archaea, Sulfolobus solfataricus (LacS) (derived from lacS gene) and Pyrococcus furiosus (CelB) (derived from celB gene) was optimized. The performance of these enzymes under extreme reaction conditions, temperatures up to 95°C and lactose concentrations up to 90% (w/v), were studied.
The aim of this study was to thoroughly investigate the possibility of using enzyme catalyzed hydrolysis and alcoholysis of ester bonds in vitamin A and E esters to facilitate their determination in different food formulas. Two vitamin esters, retinyl palmitate and α-tocopheryl acetate were used as model compounds and two food formulas, milk powder and infant formula, were used as model matrices.
The stability of hydroxynitrile lyase from Hevea brasiliensis has been studied in organic solvents. In dry solvents, the enzyme had half-lives in the range 1400-2500 hours. The enzyme half-life was one order of magnitude lower if the medium was water saturated. The substrates, aldehyde and hydrogen cyanide, were found to promote enzyme deactivation. The deactivation increased with substrate concen
The selectivity of preparations of α-chymotrypsin immobilized on Celite or polyamide and carrying out syntheses of di- and tripeptides in acetonitrile medium were studied. The study concerns the effect of mass- transfer limitations on three different kinds of selectivity: acyl donor, stereo- and nucleophile selectivities, defined respectively as the ratio of initial rates with different acyl donor
The addition of polyethyleneimine with a molecular weight of 2000 to chloroperoxidase from Caldariomyces fumago dramatically improved the stability of the enzyme towards peroxide dependent inactivation. The rate constant for the H 2 O 2 -dependent inactivation of chloroperoxidase decreased from 0.0016s -1 to 1.1 * 10 -5 s -1 in the presence of 1% polyethyleneimine. The stabilising effect towards
The hydrolysis and transphosphatidylation of lysophosphatidylcholine (LPC), with a partially purified preparation of phospholipase D (PL D) from Savoy cabbage, was investigated. These reactions were about 20 times slower than the hydrolysis of phosphatidylcholine (PC) in a micellar system. For the transfer reaction, 2 M glycerol was included in the media, which suppressed the hydrolytic reaction.
Sequence analysis of Candida rugosa lipase 1 (LIP1) predicts the presence of three N-linked glycosylation sites at asparagine 291, 314, 351. To investigate the relevance of sugar chains in the activation and stabilization of LIP1, we directed site mutagenesis to replace the above mentioned asparagine with glutamine residues. Comparison of the activity of mutants with that of the wild-type (wt) lip
