Recent studies on enzyme reactions in organic solvents are reviwed. The reactions are classified into three categories : heterogeneous, biphasic, and homogeneous systems. The following subjects are described and discussed about the heterogeneous system : 1) the maximal expression of enzyme activity in organic solvents in terms of water content, hydration of enzyme, and equilibrium of water between enzyme and substrate solution, 2) solvent effect on the catalytic power of enzyme, 3) thermostability and thermoreactivity, and 4) applications of the enzyme reactions to synthetic chemistry.
Direct conversion of methane to desirable fuels and chemicals by its partial oxidation is an attractive subject from both academic and industrial points of view. In the last decade oxidative coupling of methane has been extensively investigated and the recent progress on refinement of catalyst for this reaction brings about a possibility of establishment of a economical process for production of gasoline from natural gas through oxidative coupling. In this paper a current R & D of catalytic chemistry for direct conversion of methane to ethylene and higher hydrocarbons is reviewed as well as the cross-coupling between methane and other hydrocarbons to valuable hydrocarbons using methane as C1 source with examples taken from our recent studies.
The rates of keto-enol tautomerization of 2- (p-ubstituted benzoyl) acetophenones in the absence of catalyst in methanol containing 20 vol% water at 2030°C were spectrophotometrically measured. Absorption curves of pure keto and enol forms were obtained by analysis of obtained absorbance and wavelength with a personal computer. Conversion percentage was obtained from calibration curves. The reactions obeyed the reversible first-order rate equation : Rate=k1 (a-c-x) -k-1 (c+x), where, k1 and k-1 are first-order rate constants for ketonization and enolization : a, c and x are concentrations of the whole tautomers, keto form at the initial time and consumed enol form at time t, respectively. Each entropy in the ketonization or enolization seems to indicate the presence of transition state with aggregated water molecule. A plot of log k1 (or log k-1) vs. log CH2O gave a straight line with a slope of ca. 3 for the ketonization and enolization as well. These findings support a mechanism in which a hydrogen bonding annular complex is produced by three molecules of water between enol hydrogen and the methine carbon in ketonization and/or methylen hydrogen and benzoyl oxygen in enolization.
The amounts of sterols in vegetable oils were measured by a simple enzymatic method. The applicability of the enzymatic method to determination of various sterols was investigated. 4-Desmethylsterols were oxidized quantitatively by cholesterol oxidase to give satisfactory analytical result. However, 4-mono and 4, 4-dimethylsterols could not be oxidized by cholesterol oxidase. It was also possible to analyze unsaponifiable matter in vegetable oils by this method due to the quite low content of 4-methylsterols.
Useful methods for the stabilization of lipase (EC 184.108.40.206) in an aqueous solution and in the immobilized insoluble state are presented. (NH4)2SO4 was found to have no effect on lipase stabilization in a range up to 10%. However, such effect was quite prominent at 20% concentration to give 66% of the initial activity indicated (200 units per mL) after 100 days of storage at 35°C (Fig.-2). The intensity of this effect became 1.5 times as much following the addition of a small amount of Na2SO3 (0.25%). Essentially the same results were observed for solution mixtures of 20% Na2SO4 and 0.25% Na2SO3 (Fig.-3). This salt effect was exerted to a greater extent than in the case of polyols and their derivatives (Table-1). A number of carriers which adsorb lipase were tested for lipase activity (Table-2). Among them, Amberlite CG-50 on which lipase was bound covalently in 50% yield based on lipase activity was found to maintain about 60% the initial activity with 270 days of storage at 35°C (Fig.-4). Basically the same was noted for the lipase absorbed on Amberlite CG-50 in 42.8% yield (Fig.-4). The reason for the high stability of lipase immobilized on Amberlite CG-50 may possibly be the suitable carrier structure on which lipase is adsorbed without losing its three dimensional enzyme moiety and also the balanced hydrophilic and lipophilic carrier properties which facilitate the approach of the substrate (olive oil) onto the carrier surface. The two practical and simple methods of lipase stabilization presented in this report may serve to promote the field of biotechnology in which lipases are used.
The detergency performance of sodium and various alkylamine salts of spiculisporic acid (4, 5-dicarboxy-4-pentadecanolide; S-acid) and the corresponding open-ring acid of analogous compound (3-hydroxy-1, 3, 4-tetradecanetricarboxylic acid; O-acid) were studied for a comparison with those of commercially available synthetic detergents such as sodium dodecylbenzenesulfonate, hexaethyleneglycol monodecyl ether, and sodium laurate. The di-meutralized n-hexylamine salts of S-acid and O-acid were found to have the highest ability for soil removal. This parameter of monosodium salt of S-acid exceeded that of disodium salt and was essentially the same as those of synthetic detergents. Soil removal ability of the detergent was shown to be closely correlated to interfacial tension at oil-water interface. The detergent having lower interfacial tension showed better detergency performance.
The qualitative characteristics of household margarine for cooking purpose, recently noted as a new field of household margarine by manufacturers, were clarified on the basis of various chemical and physical parameters of 12 brands of margarine (vegetable fat type 6; milkfat blend type 2 and vegetable-animal mixed fat type 4). 1) Analytical results for sterols and fatty acid composition showed the vegetable-animal mixed fat type to contain hardened fish oil as animal fat, and the other types, hardened vegetable oils. Six brands among the tested margarine contained low erucic rapeseed oil. 2) The content of total tocopherols in the household margarine was 16.840.8 mg/100 g (x27.6 mg/100 g), this being less than that for margarine for spreading previously as reported elsewhere. Tocopherol, labelled on the packages of eight brands, including all vegetable-animal mixed fat type, might be added as an antioxidant, since the γ-form is present in a much greater amount than the α-form in all the brands. 3) In an oven test at 60°C, the oxidative stability of the milkfat blend type was relatively quite good, but peroxide value of the margarine, whose percentage of 18 : 2 fatty acid exceeded 15%, rose more rapidly than that of any other type. Prooxidant metals, such as iron, copper or nickel were present in only trace amounts, this being not related to increase in peroxide values. 4) From the curves of hardness index and solid fat content, different types of the tested margarines were shown to be harder in the order of vegetable fat type<vegetable-animal mixed fat type<milkfat blend type, particularly in the lower temperature region. The margarine for cooking purpose oiled-off with relative difficulty even at room temperature (about 20°C).