Studies on enzymatic conversion of lipids and enzymes catalyzing lipids conversions that have been carried out by the author for these 20 years are reviewed. 1) Enzymatic conversions of lipids. Various conversions involving fats and oils catalyzed by lipases or by phospholipase D are described. These include; hydrolysis of partial glycerides contained in the crude product of chemical hydrolysis of fat; factors affecting of intraesterification of ω-hydroxyfatty acid in benzene; interesterification of olive oil by immobilized dry fungus; acidolysis of fish oil to increase n-3 poly unsatureted fatty acid content; glycerolysis of fats to produce monoacylglycerol; formation of pure phospholipids by the action of transphosphatidylation of phospholipase D. An unique liquid-liquid contact mode membrane bioreactor system that is useful for fats and oils conversions has been developed. A novel concept, 'micro aqueous', has been proposed. 2) Biochemistry, production, and genetic engineering for enzymes catalyzing lipids conversions. Two assay methods of lipase's hydrolysis activity have been reexamined. Lipase produced by Fusarium oxysporum has been purified and characterized. Esterase produced by Bacillus stearothermophilus has been purified and characterized, and it has been found that it is stabilized by SH-protecting agent. Protein engineering focusing on the role of two cysteine residues involved in the esterase has been studied. Both effective productions of Pseudomonas lipase and Bacillus esterase have been realized by automatic fed-batch cultures. Gene encoding phospholipase D of Streptomyces antibioticus has been cloned and characterized and proposed a domain that may be binding site of substrate.
Study was made to determine how the amounts of solubilized water depends on the concentration of dioleyldimethylammonium chloride in cyclohexane by Karl-Fisher titration at 25°C. Using 1H-NMR and near infrared spectroscopy, the states of water in solubilization regions were examined as a function of Rw (= [H2O] / [surfactant]) at various surfactant concentrations. Three types of water were found present in different amounts within reversed micelles, that in the region below Rw=3.3 was bound directly to polar groups of the surfactant ; that in Rw=3.3 to 12.3 was held by hydrated polar groups through hydrogen bonding and that above Rw=12.3 was bulk-like. These types are discussed in relation to the formation of reversed and swollen micelles or W/O microemulsions. The surfactant concentration and minimum Rw required for swollen micelle and W/O microemulsion formation were determined.
Activated carbons surface-improved by different organic compounds were prepared and the adsorption characteristics of low-molecular weight organic compounds on these activated carbons were examined in gas and liquid phases. Methane and phenol served as adsorbates in gas phase and liquid phase adsorption, respectively. Pore volume and specific surface area of the activated carbons decreased by the introduction of acyl groups. Triphenylsilyl group introduction failed to decrease pore volume or specific surface area. In low-molecular weight organc compounds adsorption, the introduction of organic groups did not enhance the methane gas adsorptivity of the activated carbon. Phenol adsorptivity of activated carbon from aqueous solution increased as a result of increase in the hydrophobicity of the activated carbon surface due to organic group introduction.
Substrate specificity of three lipases (from Porcine pancreas, Pseudomonas fluorescence and Candida cylindracea) and the effect of organic solvent on the substrate specificity were examined in the hydrolytic reaction at various kinds of fatty acid and alkyl esters. The substrate specificity to the carbon number of acid unit in fatty acidmethyl esters was different from that in triacylglycerols. The substrate specificity to the carbon number of alkyl group in alkyl butyrates was not dependent on the lipases used. The effect of the organic solvent on the substrate specificity was not observed.