In the previous study, we found natural wax esters to be hydrolyzed by the particular commercial lipase preparations when an organic solvent was present in the reaction mixture. In all cases of vegetable wax esters, lipase activity required to bring about the same degree of hydrolysis differed signicficantly according to the enzyme source. The present study was carried out to clarify the above phenomenon, using a rice bran wax with two lipases from Candida cylindracea (Can.) and Rhizopus chinensis (Rh.). To obtain reaction products for the same degree (11%) of hydrolysis of a rice bran wax in each case, Can. lipase was required in an amount that would provide 5000 U of lipase activity, while for Rh. lipase, the amount that would give 150 U under the same reaction conditions. An assay of the above reaction products indicated Rh. lipase liberate the saturated longer-chain fatty acids constituting the rice bran wax more than Can. lipase, although no significant difference was observed in alcohol specificity under the reaction conditions tested. Also Can. lipase was inactivated much faster in the reaction mixture with the organic solvent than Rh. lipase which had previously been identified as fairly thermostable. Thus, differences in the degree of hydrolysis of the wax ester caused by both enzymes may primarily arise from those in stability and substrate specificity of the two enzymes. It is thus concluded that at least three properties of an enzyme, thermostability, stability in the reaction mixture with an organic solvent, and reactivity on long chain monoesters, are critical indexes for the screening of an appropriate enzyme or microorganism producing an enzyme which applicable to the industrial hydrolysis of natural wax esters.
The pyrolysis characteristics of 14 kinds of commercial refined oils and fats (vegetable 12, animal 2) were investigated by thermogravimetry (TG), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC). 1) When determined under a stream of air, the weight of perilla oil slowly increased from about 120 °C to 180 °C. However, the weight gains of sunflower, soybean, cottonseed and rapeseed oils were insignificant, and less than that of perilla oil. 2) The TG and DTG curves of each oil or fat showed characteristic patterns of weight reduction in the temperature range from about 300 °C to 500 °C. These patterns could be classified into four groups, based on fatty acid composition. 3) The temperatures at initial, 25%, 50% and 75% pyrolysis did not correlate to saponification values but to iodine values and the highest correlation coefficient (0.942) was obtained at the temperature for 25% pyrolysis. For no samples was correlation observed between temperature and acid or peroxide value, both being very low. 4) The initial temperature of weight reduction on the TG and DTG curves was correlated to the smoke point as determined by the Cleveland open cup method (C.O.C. method) (γ=0.887). The initial ignition temperature, found from the DTG and DSC curves as a clear peak, was correlated to the flash point determined by the C.O.C. method. However, the regression line for lard, beef tallow, palm, coconut and palm kernel oils differed from that for the other vegetable oils. Thus, it seems that the ignition temperature of the oil of known type may be used for determining the flash point.
The synergistic effects of tocopherol (Toc) and 19 kinds of amino acids on the oxidative deterioration of emulsified fatty foods were investigated. Margarine, as an emulsified fatty food, was prepared from aqueous phase with amino acids, insoluble to fat, and lard with vitamin A, β-caroctene and the mixture of d-Toc (m-Toc). Its stability toward oxidative deterioration was evaluated on the basis of change in POV and content of vitamin A and β-carotene during storage at 25 °C. 1) All amino acids contributed to enhance the effects of m-Toc on the oxidative deterioration of margarine. In particular, the addition of L-histidine (His) along with m-Toc caused its effect on margarine to be strongest, followed by those of L-tryptophan (Trp), L-lysine (Lys) and L-methionine (Met), whose effects were superior to that of dibutyl hydroxytoluene alone. 2) During storage at 25 °C, all amino acids showed the somewhat protective effect of Toc on oxidative decomposition in margarine, particularly the effect of His was strongest, followed by those of Trp, Lys and L-phenylalanine. 3) During storage at 25 °C, Met was oxidized most rapidly in margarine, and could no longer be detected after 9 months. However, methionine sulfoxide, the oxidative product of Met, appeared relatively stable and served to enhance the protective effects of m-Toc on the oxidative deterioration of margarine.
Some Aluminum salts of long-chain alkylphosphates (Al-DHP) form stiff gels in the presence of nonpolar oils such as isooctane, n-heptane, cyclohexane, p-xylene, benzene and n-hexadecane. The mechanism of gelation of the Al-DHP-hydrocarbon system and association state of Al-DHP in this system were investigated by measurement of gel hardness, differential scanning calorimetry (DSC), scanning electron microscopic observation (SEM) and polarizing technique. Above the gel/jelly transition temperature (Tc), the gel converted into a highly viscous solution, indicating the formation of linear polymeric molecules of Al-DHP. Cooling down under Tc caused this viscous solution to become a hard and staff gel. Uunder Tc, a flexible Al-DHP polymer changes to linear micro crystals. The stabilization of the gel is considerd due to formation of a well dispersed three dimensional network structure consisting of linear microcrystals. SEM observation of the gel indicated formation of a fiber network, thus supporting the above assumption. The hardness of the gel varied according to the solubility parameter (S.P.) of the solvent. The gel became hardest when the S.P. of the solvent was 8.2 to 8.75. Tc was lowest when the gel was hardest. It is thus evident that gelation is closely related to the dissolution of Al-DHP to the solvent.
Two series of new crown compounds [4 : CpAsp (n), CpGlu (n), p=10-16, n=5, 6] were prepared by the cyclization of oligoethylene glycol ditosylates with the dicaesium salt of N-acyl-aspartic or -glutamic acids (Scheme-1). The yields of CpGlu (n) were generally better than those of CpAsp (n) (Table-1). The yield and specific rotation ([α]25D of the cyclization products depended on reaction temperature (2080 °C), type of alkali metal cation (M : Li, Na, K, and Cs), and leaving group (X : TsO, Cl, and Br) in the ω, ω′-disubstituted oligoethylene glycols. The results for the synthesis of C10Glu (5) are as follow : 1) under M =Cs and X=TsO, the reaction at 40 °C gave a good yield (41%) and that at 20 °C, the largest [α]25D, 2) at M=Cs and 60 °C, the dibromide gave the best yield (74%) and the dichloride, a larger [α]25D. All the products except C10, 12 Asp (6) were water-insoluble. The cloud point, cmc (critical micelle concentration), and surface tension at cmc (cmc) were determined for the aqueous solution of C12 Asp (6). These values were lower than those of the corresponding open chain compound, C12Asp (6) OH, indicating a decrease in hydrophilicity caused by cyclization of oxyethylene chains. C16Asp (5, 6) was highly efficient as a phase transfer catalyst in the halogen-exchange reaction.
The following oligomers containing ether linkages on their backbone were prepared by ring opening polymerizations of the corresponding oxirane derivatives : poly (sodium glycidate) (PG), poly (sodium 3, 4-epoxybutanoate) (PEB), poly (sodium glycidylthioacetate) (PGTA), poly (sodium glycidyloxyacetate) (PGOA), poly (disodium glycidyloxymalonate) (PGOM) and poly (disodium epoxysuccinate) (PES). Their building performance in detergents and biodegradability were examined and compared with those of sodium tripolyphosphate (STPP), disodium 3-oxapentanedioate (ODA) and trisodium citrate. Polycarboxylate oligomers containing ether linkages showed better building performances than those of ODA and trisodium citrate. Oligomers containing a malonate group (PGOM) showed the best, but were slightly inferior to those of STPP and sodium acrylate oligomers. These polycarboxylate oligomers containing ether linkages showed better biodegradability with activated sludge or soil bacteria. PG was biodegraded 25% and PES, more than 40% the initial oligomer within 5 days. It was found that the introduction of ether linkages to the backbone of acrylate oligomers promoted their biodegradability.