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The influence of reaction temperature on synthesis activity, product yield and nucleophile specificity for α-chymotrypsin and subtilisin Carlsberg were studied. The enzymes were immobilized on Celite and used in acetonitrile with a water content of 10%. Acyl-transfer reactions with Ac-PheOEt as acyl donor and 11 different amino acid amides and 3 dipeptides as nucleophiles were studied. The decreas
Differential scanning calorimetry was the method to investigate the thermostability of chymotrypsin. The transition temperature decreased by approx. 30°C when the dry enzyme became highly hydrated. High degree of hydration corresponded to extensive conformational changes during protein denaturation, reflected by large enthalpy values. Sorbitol, lyophilized together with the enzyme, caused the dest
The thermal inactivation of lyophilized chymotrypsin was studied at controlled water activities. At 60 °C the enzyme showed good stability except at aw 0.97, whereas at 75 °C considerable inactivation occured at most water activities. Increasing the amount of buffer on the preparation decreased the stability significantly. The optimal temperature of enzymatic activity was increased 14 °C, when the
Acyl migration in 2-monoolein dissolved in solvents under conditions common in lipid modification reactions has been studied. The effects on acyl migration of solvent, incubation temperature, water activity, polar additives and solid additives have been investigated. Extensive acyl migration occured in aliphatic hydrocarbons and water-miscible alcohols under dry conditions. The acyl migration rate
Methods used for the regeneration of cofactors in organic media are reviewed. Substrate-driven regeneration methods include the use of a second substrate of the same enzyme and the use of a second enzyme and its substrate. The use of mediators in oxidoreductions is described and examples of photochemical and electrochemical regeneration methods are presented. General problems and possibilities of
Synthesis of partial glycerides in a solvent-free system has been investigated with various acyl donors and glycerol as substrates and a 1,3-specific immobilized lipase to catalyze the reaction. Capric acid was the most efficient acyl donor, compared with ethyl caprate and tricaprin. However, to obtain a high yield of dicaprin and a low amount of tricaprin, ethyl caprate was the acyl donor of choi
α-Chymotrpysin (EC 3.4 21.1) was immobilized by deposition on celite and subsequent cross-linking with glutaraldehyde. The effects of different mixtures of aqueous buffer and acetonitrile on the immobilized preparation were evaluated using a dipeptide synthesis as model reaction. The initial reaction rate at 6-95% of water increased with increasing water content. The maximum yield of peptide had t
A depeptide synthesis was drastically influenced by the reaction temperature, in the range from −30° to 25°C. This article shows the kinetic reasons of this effect. α‐Chymotrypsin was immobilized on celite and used in four different water‐miscible solvents containing small amounts of water‐miscible solvents containing small amounts of water. The reaction studied was the aminolysis of N‐acetyl‐L‐ph
The effect of the addition of sorbitol on the activity and stability of enzymes was examined by monitoring transesterification reactions performed in organic media at various water activities (aw = 0.08 to 0.97). Lipases from Chromobacterium viscosum and Candida rugosa immobilized on celite, and chymotrypsin, free or immobilized on celite, were used. When the sorbitol‐containing enzymes were emplo
A novel total enzymatic synthesis of [Leu]- and [Met]-enkephalin derivatives was accomplished in low-water content systems at a preparative scale. α-Chymotrypsin, papain, thermolysin and bromelain adsorbed on Celite were used as catalysts. Organic solvents such as acetonitrile and ethyl acetate with small amounts of buffer added or at specific water activity were used as reaction media. Simple rea
Lipase-catalyzed transesterification of high-oleic-acid rapeseed oil with stearic acid or methyl stearate was investigated. High yields of 1,3-distearoyl-2-monooleyl glycerol (36%) and 1(3)-2-dioleyl-1(3)-monostearoyl glycerol (27%) with small incorporation of stearic acid in the 2-position were obtained by using lipase from Rhizopus arrhizus immobilized on polypropylene powder and ethyl stearate
Noncovalent complexes were formed by lyophilization of aqueous solutions containing horse liver alcohol dehydrogenase, NAD+ and a polymer [ethyl cellulose or poly(vinyl butyral)]. The complexes expressed higher specific catalytic activity in organic solvents as compared to a corresponding amount of enzyme deposited on to Celite or lyophilized enzyme powder. The noncovalent complexes were soluble i
In order to evaluate whether there are differences with regard to functionality in starch gel modification between 1‐and 2‐monoglycerides, the gelatinisation of potato starch in the presence of monolaurin, monopalmitin and monoolein has been examined. When the temperature was increased by 1°C/min from 20°C to 80°C there was a significant difference in gel volume between samples containing 1‐monola
