Synthesis of fatty acid esters from acid oils using lipase B from Candida antarcticaEsterification of corn and sunflower acid oils with straight-and branched-chain alcohols were conducted using lipase B from Candida antarctica (Novozym 435) in n-hexane. Sunflower acid oil consisted of 55.6% free fatty acids and 24.7% triacylglycerols, while the free fatty acids and triacylglycerols contents of corn acid oil were 75.3% and 8.6%, respectively. After 1.5 h of methanolysis of sunflower acid oil, the highest fatty acid methyl ester content (63.6%) was obtained at 40 7C and the total fatty acid/methanol molar ratio was 1/1, using 15% enzyme based on acid oil weight. The conversion of both acid oils with straight-and branched-chain alcohols was not significantly affected by the chain length of the alcohols. However, the lowest fatty acid methyl ester content (50%) was obtained in the reaction of corn acid oil with methanol. Sunflower acid oil was converted to fatty acid esters using primer alcohols such as n-propanol, i-and n-butanol, n-amylalcohols, n-octanol, and a mixture of amylalcohol isomers, resulting in a fatty acid ester content of about 70% at 40 7C.

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In this study, the esterification of oleic acid with a fraction of fusel oil was investigated. The variables that affect ester yield, such as temperature, molar ratio of oleic acid to alcohol, and amount of catalyst, were determined. Powdered silica gel was chosen to remove water instead of granular silica gel, magnesium sulfate, or benzene. The behavior of amyl alcohols and the fusel oil fraction was compared. The esterification reaction was carried out under the reaction conditions selected as optimal, and the ester conversion of the reaction was 97.3%. The product mixture compressed products, excess reactants, catalyst, and desiccant. Oleate ester and oleic acid (2.7%) were obtained using the refinement steps of filtration, evaporation, washing with distilled water, and drying over sodium sulfate. FIG. 1. Comparison of ester conversions of reactions carried out at different temperatures. FIG. 2. Comparison of ester conversion for reactions carried out at different oleic acid/fusel oil fraction molar ratios.FIG. 4. Comparison of the ester conversion of reactions using the fusel oil fraction and amyl alcohols.

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Nigella sativa L. seed lipase isolated from defatted seeds was partially purified and used as catalyst in transesterification reactions. Purification of an ammonium sulfate-precipitated sample (at 35% saturation, Nigella PL) by DEAE ion-exchange chromatography increased the specific activity from 13.9 to 156.7 U/mg protein. Nigella PL and Nigella CPL (the partially purified enzyme sample obtained by DEAE ion-exchange chromatography) catalyzed the transesterification of vinyl acetate with octanol, with racemic sulcatol (6-methyl-5-hepten-2-ol), and with racemic trans-sobrerol (trans-p-menth-6-ene-2,8-diol) in different organic solvents. Both activity and enantioselectivity of the enzyme samples used for these biotransformations were affected by the nature of the organic solvent.Lipases, which catalyze not only the hydrolysis of TAG but also their synthesis from glycerol and FFA, can be used in the production of detergents, foods, pharmaceuticals, and other synthetic organic materials (1).Lipases can be obtained from mammals, yeast, bacteria, and higher plants. To date, most industrial lipases have been produced from fungal sources. These enzymes are usually well characterized, but lipases from higher plants generally have not yet been investigated in detail despite the fact that they may display different properties that could be exploited for industrial or technical purposes. Lipases are present in oil seeds, such as rape (Brassica napus), mustard (Sinapis alba), and cereals (2,3). Usually these enzymes are absent in dormant seed and are produced during seed germination. However, Nigella sativa L, also known as black cumin or fennel flower, contains active lipases even in its dormant seeds (3-5).FA selectivity of lipases has been utilized to enrich for FA (or of their derivatives) from naturally occurring mixtures (6). More recently, lipases have been used as biocatalysts for the enzymatic resolution of racemic substances to produce pure enantiomeric drugs (7,8).Nigella sativa L. is a member of the Ranunculaceae family (9). Its capsule-shaped fruit contains the black-colored, oval, and three-faced seeds. Owing to their aromatic nature, Nigella sativa L. seeds are used as condiment or spice in cooking.Crude and immobilized N. sativa L. lipases are effective biocatalysts for the hydrolysis and glycerolysis of TAG and for the esterification of FFA (5,10-12). A crude lipase sample from N. sativa L. seeds was immobilized by adsorption on Celite 535 from phosphate buffer solutions at pH values varying from 5.0 to 8.0 at 25°C, and pH 6 was established to be optimal for adsorption (12).The goals of this study were to obtain crude and partially purified samples of lipase(s) and to investigate the efficiency of these enzymatic preparations for transesterification reactions in organic solvents. EXPERIMENTAL PROCEDURESMaterials. Nigella sativa L. seeds from the Denizli region of Turkey were purchased locally. The proximate compositions of the seeds, determined according to standard AOCS methods (13), were 9.4% moisture, 4% a...