The ability of the commercial lipolytic enzyme Lipoprime 50T to catalyze the biotechnologically important synthesis of the biodegradable and environmentally acceptable trimethylolpropane (2-ethyl-2-(hydroxymethyl)-1,3-propanediol) ester of oleic acid was investigated. Simple and accurate thin-layer chromatography and computer analysis methods were used that enable one to follow changes of all reaction mixture components simultaneously. The processes of transesterification and esterification were compared. The effects of the molar ratio of the substrates, reaction temperature, time, and medium on the composition of the reaction mixture were analyzed. Esterification was determined to be more preferable than transesterification in both studied solvents. Under the optimal conditions identified (15% w/w water, temperature 60°C, trimethylolpropane to oleic acid molar ratio 1:3.5, and reaction time 72 h), the highest trimethylolpropane trioleate yield of around 62% and trimethylolpropane mono-, di-, and trioleate overall yield of about 83% were obtained. Although the yields are not high enough for industrial application, the process shows the potential to be optimized for higher yields in the near future as the conversions were obtained at ambient pressure, whereas many other processes described in the literature are conducted under vacuum at a specific pressure.
The lipase from Pseudomonas mendocina 3121-1 was found to be homogeneous with a molecular mass of 30 kDa by SDS/PAGE. It is composed of two identical subunits. A molecular mass of 62 kDa was determined by gel chromatography on a Toyopearl HW-55F column. Some physicochemical properties of the lipase were investigated using p-nitrophenyl butyrate (p-NPB), Tween 80 solution and Sigma olive-oil emulsion as substrates. The optimum temperature was determined to be 52 degrees C with p-NPB, in the range 50-60 degrees C with Tween 80 and in the range 50-65 degrees C with olive-oil emulsion. The optimum pH was determined to be in the pH range 7.2-7.5, both with Tween and the emulsion, but was unusually alkaline (pH 9.5) with p-NPB. The enzyme was activated for p-NPB hydrolysis by thermal treatment up to 60 min at 60 degrees C, pH 7.0-8.2, but was rapidly inactivated at 70-80 degrees C and at pH 7.0. The lipase was shown to be more thermolabile at 60 degrees C with respect to other two substrates. Using the emulsified substrate, no activity was obtained after preincubating the enzyme for 30 min at 70 degrees C. The enzyme was found to be pH-tolerant when stored at 20 degrees C, pH 6.3-10.3 (100 mM Briton-Robson buffer) as the half-life (t(1/2)) was more than 240 h when p-NPB was used as the substrate. By contrast, the pH-stability range was more narrow (pH 8.0-10.5) with olive-oil emulsion. The effect of various metal ions and EDTA depended on the nature of the substrate.
Magnetic properties of nanocrystalline spherical Fe 3 O 4 particles deposited on a chitin surface were investigated, and the mechanisms of precipitation and magnetization were explained. The main investigations were performed by means of Mö ssbauer spectroscopy and by measurements of the saturation magnetization. The size of chitin particles used as magnetic carriers was 0.05-0.25 mm, and the Fe 3 O 4 particles were precipitated from a ferrofluid. The experimental results agreed well with the theoretical model of the superferromagnetic state. The remaining magnetic properties in nanometric Fe 3 O 4 particles were explained by collective magnetic interactions. It has been found that the saturation magnetization of magnetic carriers --nanocrystalline Fe 3 O 4 particles deposited on a chitin surface --is two or three times lower than that of bulk Fe 3 O 4 crystals of the same amount.
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