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.

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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.

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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.

This paper deals with the accumulation of lipids, carbohydrates and proteins in the biomass of the green algae Chlorella vulgaris that is cultivated in the municipal wastewater of Vilnius City. The growth rate of the culture on different chemical compositions of media was investigated. Dependence of lipid, carbohydrate and protein content on total phosphorus and nitrogen initial concentrations in wastewater and removal of nutrients was investigated. Data showed that the higher amount of total nitrogen is the main factor leading to a higher rate of biomass increase. The study showed that Chlorella vulgaris is capable of very efficient nutrient removal from wastewater (up to 86% of total nitrogen and 87% phosphorus was removed). Data showed that there is strong correlation between the initial concentration of nitrogen, and in some cases phosphorus, in the media and content of proteins and carbohydrates in the biomass. A higher amount of nitrogen in the starting media leads to a higher amount of proteins and a lower amount of carbohydrate in the biomass. There was no correlation found between the initial nitrogen or phosphorus concentration in the media and content of lipids in the biomass.

Lipases of different origin were screened for substrates and different reactions from the practical approach to search for the optimal conditions for biodiesel component production. The commercial lipases under analysis were shown to be specific to p-nitrophenyl fatty acid esters of medium chain length, although Lipolase100 LEX also showed a relatively high hydrolytic activity on p-nitrophenyl palmitate. The soluble Enterobacter aerogenes lipase was shown also to be the most active when hydrolysing medium-chain-length p-nitrophenyl fatty acid esters. The specificity of immobilized commercial lipases did not change as compared with soluble analogues. The immobilized Enterobacter aerogenes lipase showed no significant differences of activity towards p-nitrophenyl butyrate and medium-chain p-nitrophenyl fatty acid esters versus the attached enzyme on polyurethane and chitosan and also showed the highest hydrolytic activity on p-nitrophenyl caprylate as for soluble lipase. Enterobacter aerogenes lipase-catalyzed esterification of oleic acid with oleoyl alcohol was a long-lasting process still in progress after 91 hours. The lipase showed the highest catalytic activity when esterifying oleic acid with ethanol and 1.2-ethanediol. The enzyme slightly esterified the acid with 1.3-propanediol and was almost inactive for esterification with 2-hydroxyethyl ether. Enterobacter aerogenes lipase more efficiently hydrolysed camelina oil than rapeseed oil, considering the former to be an alternative source to be converted into biodiesel components. Methanolysis of rapeseed oil catalyzed by the lipase adsorbed on chitin was also a long-lasting process still in progress during 124 hours. The optimal glycerol-tricaprylate-to-methanol ratio was 1 : 1 for methanolysis of the substrate catalysed by Resinase HT lipase immobilized on a polyurethane support. The lipase was completely depressed at the ratio 1 : 3.

The goal of obtaining enzyme forms with higher catalytic activity, greater stability, and improved reusability has been pursued for the last few decades. Various novel biocatalyst designs have been created, and protein-coated microcrystals (PCMCs) are one of them. PCMC is an enzyme immobilization method based on simultaneous precipitation of protein and carrier, forming micron-sized enzyme-coated crystals. Highly active Rhizomucor miehei lipase (RML) PCMCs were prepared by immobilizing the protein onto K2SO4 as a carrier salt in acetone as a precipitating solvent. The formation of RML PCMCs was confirmed by scanning electron microscopy. Preparation of RML PCMCs was optimized by response surface methodology (RSM). Obtained PCMCs were found to be more active and stable during p-nitrophenyl palmitate hydrolysis in n-hexane, compared to liquid RML. The enzymatic activity and temperature optimum increased from 0.011 U/mg(soluble) lipase to 8.70 U/mg(immobilized) lipase and from 30 to 37 °C, respectively. Additionally, the ability of RML PCMCs to catalyze flavor ester 2-phenethyl octanoate synthesis was investigated. Some reaction parameters were optimized, resulting in 80 % conversion within 1 h with an enhanced reusability, compared to commercial immobilized RML preparation. Thus, PCMCs offer a cheap and effective technology for obtaining highly active lipase preparations for biocatalysis in organic media.