Glycerolysis Reaction Research Articles

Microwave‐Assisted Chemistry of Carbohydrates

AbstractFor Abstract see ChemInform Abstract in Full Text.

Solvent engineering applied to lipase‐catalyzed glycerolysis of triolein

AbstractSolvent engineering was applied to lipase‐catalyzed glycerolysis of triolein for the selective synthesis of monoolein and diolein. The effect of different binary mixtures of n‐hexane and 2‐methyl‐2‐butanol (2M2B) on the selective production of mono‐ or diacylglyceride was established. Conditions for high selectivity toward monoolein synthesis were enhanced from 10.6 mol% in pure n‐hexane to 64 mol% in 2M2B. On the contrary, the highest production of diolein, corresponding to 62 mol%, was achieved in n‐hexane. Concerning triolein conversion, the best results were obtained in 100% 2M2B, with a conversion of 75%. The effect of the n‐hexane/2M2B ratio on diolein regioisomer production during triolein glycerolysis was also evaluated. Two different profiles of diolein regioisomers were observed as a function of solvent composition: Although the production of the 1,2‐diolein isomer was favored as the proportion of 2M2B in n‐hexane was increased, the 1,3‐isomer was preferentially synthesized in reactions where n‐hexane was the predominant solvent. When 100% n‐hexane was used as a solvent, 1,3‐diolein comprised 72 mol% of the total diolein population (58 mM). On the contrary, when the reaction was carried out in 100% 2M2B, the total concentration of diolein was lower (21 mM) but the 1,2‐diolein regioisomer was preferentially formed (89%). These results were explained as a consequence of the different extents of hydrolysis‐synthesis reactions involved in the glycerolysis process, which are strongly dependent on solvent mixtures and water concentration. Finally, some advantages of the use of binary mixtures of solvents compared with other strategies applied to glycerolysis reactions are discussed.

Emulsifiers from solid and liquid polyols: different strategies for obtaining optimum conversions and selectivities

The present paper provides a general overview of the factors involved in both the kinetics and the selectivity of partial acylation reactions of polyols (sugars). Different kinetic strategies for maximum production of intermediate esters of various polyols and monosaccharides are reported and discussed. Physicochemical requirements for obtaining maximum selectivities and complementary strategies for reducing reaction times are discussed. The reactions studied include glycerol, glucose, fructose, mannose, sorbitol and an alkyl glucoside as precursors. The high selectivity towards the monoglyceride in the presence and absence of a solvent has been attributed to a combination of the precipitation of the desired ester, use of glycerol in excess and the relatively low solubility of the fatty acid in the system. Unlike the reaction in the presence of a solvent, the reaction in a solvent-free medium produces the diester first. The monoester only accumulates in the medium as a consequence of disproportionation and glycerolysis reactions of the diester formed earlier. Selective esterification of solid sugars (polyols) which have an intermediate solubility in acetone is favored at low temperatures at which a sufficient amount of polyol dissolves and concurrent precipitation of the desired product can be achieved. By contrast, use of elevated temperatures is more appropriate for selective partial esterification of polyols, which are the most soluble in the solvent employed. Polyols (sugars) which are the less soluble into the liquid reaction phase cannot be easily esterified. Diffusional limitations on the rate of dissolution of the solid precursor can be minimized by increasing the surface area of the solid polyol.

Solvent‐free glycerolysis catalyzed by acetone powder of Nigella sativa seed lipase

AbstractThe solvent‐free glycerolysis of used sunflower oil catalyzed by acetone powder of Nigella sativa seeds was investigated. The highest partial acylglycerols yield was obtained at 60°C. The glycerolysis reactions, conducted at molar ratios of 1:1, 2:1, and 3:1 of oil to glycerol keeping the acetone powder content at 30% based on oil weight and the temperature at 60°C, approached equilibrium after 2 h. The highest partial acylglycerol content of the products was 66% (1:1 molar ratio) and 60% (2:1 molar ratio).

Multiple intensified performance of an enzyme-catalyzed reaction in organic medium.

A lipase-catalyzed glycerolysis reaction (a transesterification between polyunsaturated fatty acid ethyl ester [PUFA] and glycerol) was investigated. Its performance was multiply intensified by (1) using a lipase having high specific activity, high activity in organic solvent, and high tolerance in organic solvent; (2) immobilization on fine CaCO3 powder (cheap and safe material, easy physical adsorption method of immobilization, reusable); (3) reaction in vacuo resulting in 100% conversion and effective avoidance of oxidative deterioration of PUFA; (4) high volumetric productivity because of no use of solvent; and (5) no need of further separation and purification of the oil product. It is emphasized that performance of biocatalytic reactions in organic media should be enhanced manifold for industrial implementation.

Solvent‐free glycerolysis catalyzed by acetone powder of Nigella sativa seed lipase

AbstractThe solvent‐free glycerolysis of used sunflower oil catalyzed by acetone powder of Nigella sativa seeds was investigated. The highest partial acylglycerols yield was obtained at 60°C. The glycerolysis reactions, conducted at molar ratios of 1:1, 2:1, and 3:1 of oil to glycerol keeping the acetone powder content at 30% based on oil weight and the temperature at 60°C, approached equilibrium after 2 h. The highest partial acylglycerol content of the products was 66% (1:1 molar ratio) and 60% (2:1 molar ratio).

Alcoholysis and Strand Joining by the Flp Site-specific Recombinase: MECHANISTICALLY EQUIVALENT REACTIONS MEDIATED BY DISTINCT CATALYTIC CONFIGURATIONS

The strand joining step of recombination mediated by the Flp site-specific recombinase involves the attack of a 3'-phosphotyrosyl bond by a 5'-hydroxyl group from DNA. The nucleophile in this reaction, the 5'-OH, can be substituted by glycerol or other polyhydric alcohols. The strand joining and glycerolysis reactions are mechanistically equivalent and are competitive to each other. The target diester in strand joining can be a 3'-phosphate covalently linked either to a short tyrosyl peptide or to the whole Flp protein via Tyr-343. By contrast, only the latter type of 3'-phosphotyrosyl linkage is a substrate for glycerolysis. As a result, in activated DNA substrates (containing the scissile phosphate linked to a short Flp peptide), Flp(Y343F) can mediate the joining reaction utilizing the 5'-hydroxyl attack but fails to promote glycerolysis. Wild type Flp promotes both reactions in these substrates. The strand joining and glycerolysis reactions are absolutely dependent on the catalytic histidine at position 305 of Flp. Our results fit into a model in which a Flp dimer, with one monomer covalently attached to the 3'-phosphate, is essential for orienting the target diester or the nucleophile (or both) during glycerolysis. The requirement for this dimeric complex is relaxed in the strand joining reaction because of the ability of DNA to orient the nucleophile (5'-OH) by complementary base pairing. The experimental outcomes described here have parallels to the "cleavage-dependent ligation" carried out by a catalytic variant of Flp, Flp(R308K) (Zhu, X.-D., and Sadowski, P. D. (1995) J. Biol. Chem. 270, 23044-23054).

Activity and stability of lipase in the solid-phase glycerolysis of triolein

Lipase-catalyzed glycerolysis of triolein was studied in a solid-phase system. The activity and stability of three bacterial lipases in crude and purified forms were examined. Most of these lipases were suitable for the high-yield synthesis of monooleylglycerol. With crude lipase from Chromobacterium viscosum, 96% monooleylglycerol concentration was achieved. In the case of pure lipase from Pseudomonas cepacia, immobilization on Celite was necessary. This led to a strong increase in the long-term stability and final monooleylglycerol concentration. Immobilization on Sepharose™ led to less stable and active lipases from P. cepacia. In general, the highest loss in stability was observed in the first reaction hour, and purified lipases were less suitable. Furthermore, six yeast and mold lipases were employed as catalysts in the model reaction system. Most of them have been neither very stable nor very active in the glycerolysis reaction. Only purified lipase from Rhizopus delemar gave moderate monooleylglycerol concentrations. The addition of R. delemar at intervals influenced neither stability nor monooleylglycerol concentrations. The optimum cooling temperature for the solidification of the reaction mixture, which was necessary for high monooleylglycerol concentration, was determined to be 8°C.

Screening of commercial lipases for production of mono- and diacylglycerols from butteroil by enzymic glycerolysis

Abstract Eight microbial lipases and one animal tissue lipase were tested for their ability to support glycerolysis reactions with butteroil in the presence and absence of t -butanol to produce monoacylglycerols (MAG) and diacylglycerols (DAG). Two bacterial lipases from Pseudomonas spp. showed the greatest yield of MAG (55–60%) and DAG (24–39%) in the presence or absence of t -butanol. In contrast, lipases from Rhizopus arrhizus, R. javanicus and R. delemar produced yields of MAG and DAG of 23–25% and 36–39%, respectively, but were effective only in the absence of t -butanol. Porcine pancreatic lipase showed limited glycerolysis activity in the presence of t -butanol, yielding 4·6% MAG and 10% DAG, but was not active in the absence of t -butanol. Geotricum candidum, Muco javanicus and Candida cylindracea (C. rugosa) lipases did not support glycerolysis in the presence or absence of t -butanol. It appears possible to selectively use lipases from Pseudonomas and Rhizopus spp. to transform butteroil into blends of MAG and DAG with MAG:DAG ratios of about 0·65 to 2·3.

Control of lipase-mediated glycerolysis reactions with butter oil in single liquid phase media with 2-methyl-2-propanol

Factors affecting the progress of glycerolysis reactions with butteroil mediated by two lipase preparations (from Pseudomonas sp.) in single liquid phase mixtures containing 2-methyl-2-propanol were evaluated. Within the range of parameters evaluated, the conditions best supporting the formation of monoacylglycerols (MAG) were 25-40% butteroil substrate, 10-20 mg of enzyme/mL of substrate mixture, 35 o C, and 100-150 mg of glycerol/mL of substrate mixture (equivalent to a molar ratio of fatty acyl groups to glycerol of 0.61-0.76). Under these conditions, the percent yield of MAG formation from butteroil was 50-60% (mass fraction) relative to the other acylglycerol species and fatty acids accumulated

Control of lipase-mediated glycerolysis reactions with butter oil in dual liquid phase media devoid of organic solvent

Factors affecting the progress of glycerolysis reactions with butteroil mediated by two lipase preparations (from Pseudomonas sp.) in dual liquid phase mixtures devoid of solvent were evaluated. Within the range of parameters evaluated, the conditions best supporting the formation of monoacylglycerols (MAG) were 35 o C, 2.5-4.8% water in glycerol, and 0.33-0.44 g of glycerol/g of butteroil (equivalent to a molar ratio of acyl groups to glycerol of 0.66-0.85). Under these conditions, percent yields of MAG formation from butteroil were 50-55% (mass fraction) relative to the other acylglycerol species and fatty acids accumulated. Little interaction was observed between these critical parameters. At temperatures greater than 35 o C, up to a 50% reduction in yield of MAG was noted

Continuous glycerolysis of olive oil by Chromobacterium viscosum lipase immobilized in liposome in reversed micelles

Chromobacterium viscosum lipase which has adsorbed on liposome and solubilized in microemulsion droplets of glycerol containing a little amount of water could catalyze the glycerolysis of olive oil. Studies on the continuous glycerolysis of olive oil by the immobilized enzyme was done at 37 degrees C in continuous stirred vessel bioreactor with polysulfone membrane. The effect of the flow rate of substrate (olive oil) in isooctane on the conversion and composition of the outlet was investigated using high-performance liquid chromatography (HPLC). The conversion increased with decrease in the flow rate. And we studied the effect of water content in the glycerol-water-lipase solution on the glycerolysis reaction. The conversion to desirable products, mono- and di-olein, was improved without a substantial production of oleic acid at lower water concentrations, i.e., below 8.0% (w/v) which corresponds to a w(o) value of 0.97. At water concentration higher than 8.0% (w/v), the amount of free fatty acid was dramatically increased. Higher operational stability of the enzyme reactor, and the half-line of the enzyme continuous reaction was about 7 weeks.

Use of lipases in multiphasic systems solely composed of substrates

Three lipase‐catalyzed reactions have been investigated in relation to specificity and water dependence. The reactions in question include: the synthetic reaction between oleic acid and glycerol; the enzymatic hydrolysis of triolein; and alcoholysis/glycerolysis transesterification reactions. All reactions were carried out under solventfree conditions. In each case, the medium composition and reaction conditions were optimized in order to work at elevated substrate concentrations and to minimize the production of by‐products. Different lipase preparations have been tested in each reaction. In the synthetic reaction, the effective removal of produced water was found to be vital for the production of triolein. With water removal and glycerol amounts not higher than required by the stoichiometry of the reaction, 95% of the available oleic acid was converted to triolein in 48 hr. The production of triolein was also found to be dependent on the availability of the 1,2‐diglyceride to react with oleic acid. In the hydrolysis reaction, best conversion yields of triolein towards monoolein, diolein and free fatty acid were obtained when water was considered simply as a substrate of the reaction. In glycerolysis reactions, the reaction of triolein to give monoolein and diolein followed much the same pattern as for hydrolysis, when water was replaced by glycerol. It was shown again that near stoichiometric amounts of substrates led to the best conversion to mono‐ and diglycerides. A small excess of glycerol was found to be very inhibitory to the reaction. All possible isomers were formed during the reaction. Conversely, in alcoholysis reactions between triolein and stearyl alcohol the specificity of the lipase was upheld. Excess alcohol in this instance was found to be beneficial.

Some Characteristics of Continuous Glycerolysis of Fat by Lipase with Microporous Membrane Bioreactor

Various characteristics of the continuous glycerolysis of corn oil by pure Pseudomonas fluorescens lipase in a microporous hydrophobic flat membrane bioreactor were studied. By on-line continuous measurement of electric conductivity with a flow cell type electrode, the moisture content of the microaqueous glycerol containing the enzyme was monitored. The effect of moisturec ontent in the microaqueous glycerol on the glycerolysis reactions with the pure enzyme differed slightly from that with a crude enzyme as reported previously. The critical moisture content above which free fatty acids were formed was 3%, this being 1% less than that for the crude enzyme. The microporous hydrophobic flat membrane made of poly (tetrafluoroethylene) (PTFE) gave somewhat better conversions of the outlet product than did the polypropylene membrane at the same flow rates of the oil. Calcium chloride dissolved in the glycerol-water-lipase solution stabilized significantly the enzyme under non-reactive conditions without oil phase but destabilized it slightly during continuous reactions with oil.

Glycerolysis of fats and methyl esters — Status, review and critique

AbstractWith the possible exception of catalytic hydrogenation, perhaps no unit operation within the realm of oleochemistry is as thoroughly complex as that of glycerolysis. Among the misconceptions and half‐truths that prevail concerning the glycerolysis of fats are the notions that it involves a strictly random distribution of acyl groups among all of the available hydroxyl groups, that the solubility of glycerol in the fat at the reaction temperature determines the yield of monoglyceride that may be obtained, that the advantageous effects of the Law of Mass Action can be realized only when the reaction media is in ultimate homogeneity, in other words, complete mutual solubility, and, more importantly, that there is an equivalence of emulsification properties for the chief products of glycerolysis, i.e., the α‐and β‐monoglycerides, in both food and industrial emulsification. Numerous examples from international literature establish the limitations which prevail in temperature, agitation and use of excess of glycerol in batch glycerolysis reactions, but the practical limits for glycerolysis undersuperemulsification conditions remain to be established. The disadvantages of glycerolysis in homogeneous solvents still are insufficient to justify the use of those that are available, but the use of both pressure and gaseous catalysts such as carbon dioxide appear to offer the greatest hope for improvement in yields. Substantial energy savings may dictate the choice of methyl ester glycerolysis processing for future plants, especially those in the international sphere. Pros and cons of monoglyceride analytical methodology are evaluated.

Molecular weight distribution in alkyd resins. Part II. Castor oil and hydrogenated castor oil alkyds

AbstractAlkyds prepared from castor and hydrogenated castor oils have been prepared direct from the oil and by first subjecting the oil to a glycerolysis reaction. The molecular weight distributions of the alkyds have been measured in solvent systems designed to separate predominantly on polarity and molecular weight. The properties of the alkyds in stoving enamels have been evaluated. The results are discussed in relation to existing theories relating processing conditions to molecular weight distribution in alkyd resins. Previous suggestions regarding the reactivity of the hydroxyl groups in the oil molecules are not consistent with the results obtained in this study.

Glycerolysis of marine oils and the preparation of acetylated monoglycerides

ConclusionsThe glycerolysis reaction was applied to menhaden, tuna, herring, sardine, and salmon‐egg oils. Optimum reaction time for the preparation of α‐monoglycerides was found to vary, reproducibly, from 45 to 60 min., depending on the particular kind of marine oil employed. The method was suitable for the preparation of kilogram quantities.A laboratory method for the prepagation of kilogram quantities of highly pure acetylated α‐mono‐glycerides was developed. Both the glycerolysis mixtures from marine oils and their acetylated products were light in color and substantially free of odor.Thin‐layer silicic acid chromatography, as described here, was found suitable for the analysis of acetoglycerides from marine oils. The work indicated that the method may have wide use for the separation and identification of other lipid classes as well.