[Catalytic properties of lipase adsorbed on nanocarbon-containing mesoporous silica in esterification and transesterification reactions].

Nanocarbon-containing mesoporous silica covered with a varying amounts of nanostructured carbon of different morphologies were used as supports to immobilize Thermomyces lanuginosus lipase. The catalytic properties of the prepared biocatalysts were studied in both the transesterification of vegetable (linseed) oil in the presence of ethyl acetate and the esterification of the fatty acid (capric C10:0) in the presence of secondary (isopropyl or isoamyl) alcohols. The physico-chemical characteristics, such as the amount of adsorbed lipase, its specific activity, and the dependence of the activity and stability of the prepared biocatalysts on the support type were evaluated. The Michaelis-Menten kinetics was studied in the esterification of capric acid with isoamyl alcohol. The prepared biocatalysts were shown to retain up to 90% activity for >1000 h in the synthesis of isoamyl caprate. The half-time of the biocatalysts inactivation in the transesterification of linseed oil was found to be more than 700 h at 40°C.

[Recombinant strain producing thermostable lipase from Thermomyces lanuginosus immobilized into nanocarbon silica matrices and properties of the prepared biocatalyzers].

Multicomponent composite biocatalyzers with lipolytic activity have been studied. These biocatalyzers were prepared through the immobilization of a recombinant producer strain of thermostable lipase from Thermomyces lanuginosus into SiO2 xerogel, which contains a nanocarbon component, i.e., multilayered carbon nanotubes with varying diameters, and also bulblike structured carbon nanospheres ("nanobulb"). The properties of lipase were studied both in cell suspensions of a recombinant producer strain constructed based on E. coli BL21(DE3) and in the immobilized state with regard to the structure and dispersibility of the nanocarbon component used in the composition of the biocatalyzers. It was shown that the recombinant intracellular lipase exerted its activity in a reaction of tributirin hydrolysis on average comprising 50 U/mg of dried cells and had a high level of thermostability. Upon heating in olive oil at 100 degrees C, the inactivation constant and the period of semi-inactivation comprised 6 x 10(-3) min(-1) and 2 h, respectively, exceeding by one order the thermostability of lipase in a buffer solution. Biocatalyzers that contained aggregated "thick" nanotubes with a diameter of 20-22 nm had the maximum initial activity-250 U/g.

[Immobilization of a recombinant strain producing glucose isomerase on SiO2-xerogel and properties of prepared biocatalysts].

An original method of immobilization of nongrowing microorganism cells on xerogel of silicon dioxide containing insoluble hydroxyl compounds of cobalt(III) has been developed. A recombinant strain producing glucose isomerase has been constructed on the basis of Escherichia coli with the use of a gene of Arthrobacter nicotianae. It was revealed that glucose isomerase activity and stability of biocatalysts prepared on the basis of the recombinant E. coli strain was 3-5 times greater compared with the biocatalysts prepared with the use of the donor strain A. nicotianae. Under conditions of continuous hydrolysis of 3 M fructose at 62-65 degrees C in a fixed bed reactor, time of half-inactivation of the biocatalysts prepared from the recombinant strain and A. nicotianae was -60 and -25 days, respectively.

[Catalytical properties of Arthrobacter nicotianae cells, a producer of glucose isomerase, immobilized in xerogel of silicium dioxide].

Arthrobacter nicotinanae cells, producers of glucose isomerase, were immobilized in xerogel of silicium dioxide, and properties of the resulted heterogeneous biocatalysts were investigated in the process of isomerization of monosaccharide (glucose and fructose). The glucose isomerase activity of the resulted biocatalysts was shown to be 10 U/g, on average, taking into account the loss of the activity upon the immobilization, which amounted to 50% of the cell activity in suspension. The rate of the fructose isomerization increased linearly in the range of 55-80 degrees C with the temperature coefficient 1.3. The biocatalysts were stable in this range; they were rapidly inactivated, however, at increasing temperature. The half-inactivation time was six to seven h and five min or less at 80 degrees C and 85 degrees C, respectively. The half-inactivation time of heterogeneous biocatalysts was 50-90 h in the periodic process of isomerization of 2 M monosaccharides at 60 degrees C in the presence of the immobilized Arthrobacter nicotinanae cells.

[Glucose isomerase activity in suspension of Arthrobacter nicotianae cells and adsorption immobilization of the microorganisms on inorganic carriers].

Kinetics of monosaccharide isomerization has been studied in suspensions of intact, non-growing Arthrobacter nicotianae cells. Under the conditions of the study, glucose and fructose were isomerized at the same maximum rate of 700 micromol/min per 1 g dried cells, which increased with temperature (the dependence was linear at 60-80 degrees C). The proposed means of adsorption immobilization of A. nicotianae cells involve inorganic carriers differing in macrostructure, chemical nature, and surface characteristics. Biocatalysts obtained by adsorbing the cells of A. nicotianae on carbon-containing foam ceramics in the coarse of submerged cultivation were relatively stable and retained original activity (catalysis of monosaccharide isomerization) throughout 14 h of use at 70 degrees C. Maximum glucose isomerase activity (2 micromol/min per 1 g) was observed with biocatalysts prepared by adsorption of non-growing A. nicotianae cells to the macroporous carbon-mineral carrier Sapropel and subsequent drying of the cell suspension together with the carrier.

[Catalytic properties of glucoamylase immobilized on the synthetic carbon material Sibunit].

Glucoamylase (commercial preparation Glucavamorin) was immobilized by sorption on a carbon support Sibunit. Starch saccharification by the resulting biocatalyst (dextrin hydrolysis) was studied. Investigation of the effect of adsorptional immobilization on kinetic parameters of glucoamylase, including the rate constant of thermal inactivation, showed that immobilization of Glucavamorin on Sibunit resulted in a thousandfold increase in glucoamylase stability in comparison with the dissolved enzyme. Presence of the substrate (dextrins) in the reaction mixture had a considerable stabilizing effect. Increase in dextrin concentration increases the thermostability of the immobilized enzyme. The overall factor of glucoamylase stabilization adsorbed on Sibunit with the presence of 53% dextrin solutions in comparison with the dissolved enzyme approximated 10(5). The biocatalyst for starch saccharification made on the base of Subunit-adsorbed Glucavamorin had a high operational stability. Its half-inactivation time at 60 degrees C exceeded 30 days.

[Immobilized glucoamylase: A biocatalyst of dextrin hydrolysis].

Heterogeneous biocatalysts of starch conversion based on glucoamylase and carbon-containing carriers were obtained, and their biocatalytic properties in enzymatic hydrolysis of corn dextrins were studied. It was shown that the morphology of the surface carbon layer of carriers markedly affected the properties of biocatalysts. Glucoamylase that was immobilized by adsorption on the surface of carriers covered with a layer of catalytic fibrous or pyrolytic carbon had the maximum enzymatic activity and stability, whereas the biocatalysts prepared on the basis of carriers that had no carbon layer or were covered with graphite-like surface carbon had a low activity and stability.

[Immobilized yeast membranes as biocatalysts for sucrose inversion].

Yeast membranes were obtained by autolysis of various strains with relatively high invertase activity. Heterogeneous biocatalysts for sucrose inversion were made of the yeast membranes and granulated carbon-containing supports made of common natural materials: expanded clay aggregate (ECA), sapropel, and lignin. The properties of these biocatalysts were studied. It was shown that the biocatalyst activity and stability of the immobilized yeast membranes increased with reference to the initial ECA, independent of the structure of the carbon layer synthesized on the support surface. Heterogeneous biocatalysts prepared by adsorption of yeast membranes on sapropel had the greatest activity and stability, whereas lignin-based biocatalysts were relatively unstable.