Production of monoacylglycerols

The synthesis by route C is an alcoholysis reaction. The reaction proceeds as an emulsion due to the immiscibility of triacylglycerol and glycerol. Under this emulsified condition, the equilibrium concentration of the monoacylglycerol is 30% (Yamane et al., 1986). However, when the reaction is run at temperatures slightly below the melting point of the fat used, the concentration is favourably increased to 70-90% (McNeill et al., 1990 McNeill and Yamane, 1991). The reaction rate is affected by moisture content. Relatively high moisture leads to high initial reaction rates (McNeill et al., 1991) but excessive levels result in hydrolysis and production of free fatty acids. Compared to the synthetic pathways of A and B, route C seems a cheaper alternative since the primary reactive components do not include free fatty acids reactants that otherwise would have to be produced by other methods to make them available for the process. 

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Lipase-catalyzed (206, 207) and nonenzymatic glycerolysis of soybean oil (140) in SCCO2 have been used for the production of monoacylglycerols, which are important emulsifiers in food, pharmaceutical, and cosmetic industries. Nonenzymatic glycerolysis was carried out at 150-250°C and 20.7-62.1 MPa with varying glyceroEoU ratios and water contents to determine the effect of these parameters on product composition (140). The optimum conditions for the lipase-catalyzed reaction were 27.6 MPa and 70°C (206). The lower temperatures used in the hpase-cat-alyzed reaction reduces the production of undesired side products and increases the reaction efhciency (207). 

Production of Monoacylglycerols through Lipase-Catalyzed Reactions... 

Watanabe, Y., Yamauchi-Sato, Y., Nagao, T., Yamamoto, T., Ogita, K., and Shimada, Y. 2004. Production of monoacylglycerol of conjugated linoleic acid by esterification followed by dehydration at low temperature using Penicillium camembertii lipase. J. Mol. Catal. B Enzym. 27 249-254. 

Kaewthong, W Sirisansaneeyakulb, S Prasertsana, P H-Kittikuna, A. Continuous production of monoacylglycerols by glycerolysis of palm olein with immobilized lipase. Process Biochemistry, 2005, v. 40 (5), 1525-1530. 

Three basic routes (Figure 12.4) are used for enzymatic production of monoacylglycerols. In route A, monoacylglycerols are synthesized... 

Yang, T., Rebsdorf, M., Engelmd, U., and Xu, X. (2005) Enzymatic production of monoacylglycerols containing polyunsaturated fatty acids through an efficient glycerolysis system. J. 

Kittikun A, Kaewthong W, Cheirslip B. 2007. Continuous production of monoacylglycerols from palm olein in packed-bed reactor with immobilized lipase PS. Biochem Eng J 40 116-20. 

Monoacylglycerols are the monoesters of glycerol that consist of only one fatty acid attached either to the position 1(3) or 2 of the glycerol backbone. However, because both diacylglycerols and monoacylglycerols are hydrolytic products of triacylglycer-ols and phospholipids, they may be present, if any, only in negligible levels in animal and plant tissues. 

The products of triacylglycerol digestion, mainly monoacylglycerol and long-chain fatty acids, interact with bile salts to form micelles, which comprise bile salts/ monoacylglycerols/phospholipids and fatty acids. The micelle aids the absorption of monoacylglycerol and fatty... 

Correct answer = A. Pancreatic lipase hydrolyzes dietary triacylglycerol primarily to 2-monoacylglycerol plus two fatty acids. These products of hydrolysis can be absorbed by the intestinal mucosal cells. Bile salts do not inhibit release of fatty acids from triacylglycerol, but rather are necessary for the proper solubilization and hydrolysis of dietary triacylglycerol in the small intestine. Short- and medium-chain length fatty acids enter the portal circulation after absorption from the small intestine. Synthesis of apolipoproteins, especially apo B-48, is essential for the assembly and secretion of chylomicrons. 

The products of lipid digestion—free fatty acids, 2-monoacylglycerol, and cholesterol—plus bile salts, form mixed micelles that are able to cross the unstirred water layer on the surface of the brush border membrane. Individual lipids enter the intestinal mucosal cell cytosol. 

Monoacylglycerols and diacylglycerols may be genuine membrane constituents or may be products of lipolysis. Unesterified fatty acid levels... 

Studies in vitro and in rats showed that short and medium chain fatty acids and monoacylglycerols hydrolyzed from milk triacylglycerols and digestion products of sphingolipids possess strong anti-bacterial and anti-viral properties. 

Figure 26-5. Principle of the 13C-mixed triglyceride breath test. Absorption of 13C-mixed triglycerides requires prior hydrolysis by pancreatic lipase (1), which leads to production of free fatty acids (stearic acid) and monoacylglycerol [2-(l-13C)octanoylglycerol]. These metabolites are incorporated into micelles, absorbed, and transported to the liver (2). Further degradation by hepatic enzymes and P-oxidation results in formation of 13C02, which is absorbed into the bloodstream, transported to the lung, and exhaled (3). Thus, exhalation of 13C02 reflects intestinal lipolysis and is a marker of pancreatic exocrine function.

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