Biodiesel has attracted considerable attention as an alternative fuel during the past decades. The main hurdle to the commercialization of biodiesel is the cost of the raw material. Use of an inexpensive raw material such as rice bran oil is an attractive option to lower the cost of biodiesel. Two commercially available immobilized lipases, Novozym 435 and IM 60, were employed as catalyst for the reaction of rice bran oil and methanol. Novozym 435 was found to be more effective in catalyzing the methanolysis of rice bran oil. Methanolysis of refined rice bran oil and fatty acids (derived from rice bran oil) catalyzed by Novozym 435 (5% based on oil weight) can reach a conversion of over 98% in 6 h and 1 h, respectively. Methanolysis of rice bran oil with a free fatty acid content higher than 18% resulted in lower conversions (<68%). A two-step lipase-catalyzed methanolysis of rice bran oil was developed for the efficient conversion of both free fatty acid and acylglycerides into fatty acid methyl ester. More than 98% conversion can be obtained in 4-6 h depending on the relative proportion of free fatty acid and acylglycerides in the rice bran oil. Inactivation of lipase by phospholipids and other minor components was observed during the methanolysis of crude rice bran oil. Simultaneous dewaxing/degumming proved to be efficient in removing phospholipids and other minor components that inhibit lipase activity from crude rice bran oil.
A two-step method was developed for the preparation of food-grade wax. The first step involved the solventdefatting of crude wax, which gave a dark brown, dry, powdered wax with a m.p. of 75-79°C. The major impurity in the defatted wax was the dark brown resinous matter. In the second step, the resinous matter was removed by bleaching with sodium borohydride in isopropanol. This step yielded a pale yellow, odorless wax with purity higher than 99% and with a m.p. of 80-83°C. The resinous matter was a mixture of aliphatic aldehydes, fatty alcohols, and FA. High-temperature GC analysis of the purified rice bran wax indicated that it contained 11 major and 9 minor types of saturated wax esters. The major and minor peaks contained C 44 -C 64 and C 45 -C 59 wax esters, respectively. Rice bran wax was mainly a mixture of saturated esters of C 22 and C 24 FA and C 24 to C 40 aliphatic alcohols, with C 24 and C 30 being the predominant FA and fatty alcohol, respectively. The alcohol portion of the wax esters also contained small amounts of branched and odd carbon number fatty alcohols.
Human milk fat contains 20-25% palmitic acid (16:0) and 30-35% oleic acid (18:1). More than 60% of the palmitic acid occurs at the sn-2 position of the glycerol backbone. Palm oil is a rich source of both palmitic and oleic acids. The structured lipid 1,3-dioleoyl-2-palmitoylglycerol (OPO) is an important ingredient in infant formula. OPO was synthesized from palm oil by a three-step method. In the first step, low-temperature fractionation was applied to palm oil FA, yielding a palmitic acidrich fraction (87.8%) and an oleic acid-rich fraction (96%). The palmitic acid content was further increased to 98.3% by transforming palmitic acid into ethyl palmitate. In the second step, esterification of ethyl palmitate and glycerol catalyzed by lipase Novozym 435 under vacuum (40 mm Hg) was employed for the synthesis of tripalmitin. Finally, OPO was obtained by the reaction of tripalmitin with oleic acid catalyzed by Lipase IM 60. In this final step, the TAG content in the product acylglycerol mixture was 97%, and 66.1% oleic acid was incorporated into TAG. Analysis of the FA composition at the sn-2 position of TAG showed 90.7 mol% of palmitic acid and 9.3 mol% of oleic acid. OPO content in the product TAG was ca. 74 mol%. Thus, an efficient method was developed for the synthesis of OPO from palm oil.Structured lipids, such as 1,3-dioleoyl-2-palmitoylglycerol (OPO), have attracted attention recently owing to their potential pharmaceutical and nutraceutical applications. Breast milk fat is one of the main sources of nutrients and energy for infants. About 50-60% of the dietary energy that an infant needs is provided by human milk fat (HMF) (1). Palmitic and oleic acids are the two most abundant FA present in all HMF and are the most interesting from the standpoint of human nutrition. Palmitic acid represents about 25% of the total milk FA and accounts for more than 10% of the infant's total energy intake. The stereospecific distribution of FA on TAG structures in HMF plays a valuable role and influences the fate of fat absorption in infants. In HMF the saturated FA, predominantly palmitic acid, are located primarily at the sn-2 position (>60%) of the glycerol backbone (2,3), whereas the sn-1,3 positions are mainly occupied by monounsaturated FA. Thus, the main component of the milk dienoic TAG is OPO.Earlier studies used pure tripalmitin (PPP) and oleic acid for the synthesis of the structured lipid OPO (4,5). However, largescale applications of these methods are expensive because of the high cost of the substrates. To achieve an economically feasible process, it is important that starting substrates such as palmitic acid and oleic acid be isolated and purified from an inexpensive source. Palm oil is such a source for both palmitic and oleic acids, which constitute 44.0 and 39.2%, respectively, of the total palm oil FA content. Therefore, isolating and purifying these FA from palm oil may offer a considerable reduction in the cost of the substrates used to synthesize OPO.The synthesis of structured TAG is usually carried o...
Fatty acid steryl esters (FASE) and wax esters (WE) of rice bran oil (RBO) have potential applications in cosmetic, nutraceutical, and pharmaceutical formulations. FASE and WE were extracted from RBO by a modified Soxhlet extraction using hexane as the solvent. FASE and WE were then separated by storage in acetone at 10°C for 24 h. The FASE fraction was further purified by silica gel column chromatography. The contents and compositions of FASE and WE, as well as their saponified products, were identified by GC and GC-MS. The identification of FASE and WE was carried out by comparing the retention time of GC peaks and mass spectral analysis with standards synthesized in our laboratory. FASE and WE accounted for ca. 4.0% of crude RBO, of which 2.8-3.2% and 1.2-1.4% are FASE and WE, respectively. GC-MS of FASE showed five major peaks. Major FA in the FASE fraction were linoleic acid and oleic acid, which were esterified with 4-desmethyl, 4-monomethyl, and 4,4-dimethyl sterols. The contents of 4-desmethylsterol, 4-monomethylsterol, and 4,4-dimethylsterol esters in crude RBO were 76.1, 8.7, and 15.1%, respectively. WE of RBO consisted of both even and odd carbon numbers ranging from C 44 to C 64 . The major constituents were saturated esters of C 22 and C 24 FA and C 24 to C 40 aliphatic alcohols, with C 24 and C 30 being the predominant FA and fatty alcohol, respectively. The advantages of using a modified Soxhlet extraction over column chromatography are less solvent usage and larger sample size per batch with shorter operation time.Paper no. J11151 in JAOCS 83, 449-456 (May 2006). KEY WORDS:Fatty acid, fatty acid steryl ester, GC-MS, phytosterol, rice bran oil, Soxhlet extraction, TLC, wax ester.FA steryl esters (FASE) and wax esters (WE) have wide applications in cosmetic, nutraceutical, and pharmaceutical industries (1,2). FASE have water-holding properties and are widely used as ingredients of cosmetics and bath additives (3). Recently, phytosteryl ester was found to be effective in lowering plasma cholesterol concentration by inhibiting the absorption of cholesterol from the small intestine (4). This physiological activity has led to the development of functional foods, such as salad oil, dressing with added sterol, and margarine blended with FASE. Because FASE is completely soluble in TAG, there is a growing interest in the use of FASE in lipid-containing foods (5). Rice bran wax (RBW) has potential applications in cosmetic, pharmaceutical, food, polymer, and leather industries (2). A large number of patents and papers have been issued on the use of RBW in cosmetic preparations such as cold cream, drugs, and hair-conditioners. In such applications, the performance of RBW is reported to be comparable to carnauba and other waxes (2). RBW is also a rich source of high-MW aliphatic alcohols known as policosanol. Earlier investigators demonstrated the multitude of beneficial therapeutic properties associated with policosanol intake, such as the lowering of blood lipids (6). Policosanol from beeswax, which has been ...
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