Sugar fatty acid esters

A comparison of the synthesis of Z-Phe-Leu-NH2 in ten different solvents revealed that the highest overall yields could be expected in solvents where the substrate solubility is minimized. The highest yields in terms of solid product were found in solvents where both substrate and product solubility are minimized [45]. These simple rules may not hold when special factors apply, such as the formation of solid solvates. This may account for a few apparent exceptions, such as the product precipitation in dichloromethane of both a peptide and a sugar fatty acid ester [45, 63]. 

I. J. A. Baker, B. Matthews, H. Suares, I. Krodkiewska, D. N. Furlong, and C. J. Drummond, Sugar fatty acid ester surfactants Structure and ultimate aerobic biodegradability, J. Surfactants Deterg., 3 (2000) 1—11. 

FIC. 1. Lipase-catalyzed esterification for the production of sugar fatty acid esters in a stirred-tank membrane reactor. 1, pump 2, water bath 3, membrane reactor 4, condenser 5, permeate container 6, vacuum pump. 

Yan, Y., U.T. Bornscheuer, L. Cao, and R.D. Schmid, Lipase-Catalyzed Solid-Phase Synthesis of Sugar Fatty Acid Esters. Removal of By-Products by Azeotropic Distillation, Enzyme Microb. Technol. 25 725-728 (1999). 

Sarney, D.B. Vulfson, E.N. Enzymatic synthesis of sugar fatty acid esters in solvent-free media. In Enzymes in Nonaqueous Solvents Methods and Protocols (Methods in Biotechnology Vol. 15) Vulfson, E.N., Hailing, P.J., Holland, H.L., Eds. Humana Press Totawa, 2001 531-543. 

Cao, L., Fischer, A., Bomscheuer, U. T., and Schmid, R. D., Lipase-catalyzed sohd phase synthesis of sugar fatty acid esters. Biocat. Biotrans., 14 269-283, 1997. 

Cao L, Eischer A, Bornscheuer UT et al. (1997) Lipase-catalysed solid phase synthesis of sugar fatty acid esters. Biocatal Biotransfor 14 269-283 Cao L, van Langen L, Sheldon, R (2(X)3) Immobilised enzymes carrier-bound or carrier-free Curr Opin Biotechnol 14 1-8... 

There has been a resurgence in the study and use of natural surfactants in recent years. The primary reasons are that these surfactants are generally viewed as possessing the potential to have less adverse impact on the environment and to be nontoxic. Sugar fatty acid esters are one group that has been receiving renewed attention for these very reasons. Condensation of one of the reactive sugar hydroxyl functionalities with a fatty acid yields a biosurfactant that has potential application in food, cosmetics, and pharmaceuticals. 

From the mid-1950s until now there has been a significant number of publications on sugar fatty acid esters, in particular sucrose fatty acid esters. Sucrose fatty acid esters have been commercially manufactured at reasonably high volume since the early 1960s. 

This book chapter is not meant to be a comprehensive review of all the previous work on sugar fatty acid esters, as there have been many excellent review articles published on this topic. In this chapter, we have chosen to highlight either select areas of recent activity or areas where we have decided that it is worthwhile considering the background to claims. 

The synthesis of sugar fatty acid esters has recently been described in several reviews [1-6]. In the following section, we highlight recent trends and provide a brief historical overview of the production of sugar fatty acid esters with particular emphasis on the sucrose esters. 

B. Chemical Synthesis of Sugar Fatty Acid Esters... 

The enzymatic synthesis of sugar fatty acid esters has been reviewed in recent times [2,6,32]. The biocatalytic properties of lipases and the basic principles governing lipase-catalyzed esterification have been described in the... 

FIG- 2 Examples of enzyme-mediated products of ethoxylated sugar fatty acid esters. (From Ref. 61.)... 

The disappearance of sucrose ester surfactants from river water samples was studied by measuring the consequent increase in surface tension. This showed 100% primary biodegradation within 2 days [70,71]. An advantage of sugar fatty acid esters is their ready anaerobic biodegradation. Complete primary biodegradation within 2 days was also observed under anaerobic conditions [70]. 

The acute toxicity for a number of different compounds in this general class has been studied in a range of animal models. The results summarized in Table 2 reveal that no significant toxic events can be associated specifically through oral ingestion of sugar fatty acid esters. One exception appeared to be the higher dose of lard and tallow sucrose esters administered to the rat, which resulted in death. Also notable is the positive hemolytic result for sucrose monopalmitate when administered intravenously to the rat. Surfac-... 

These points apply also to the subset of carbohydrate-based surfactants that comprises a fatty acid hydrophobic group attached to a sugar-based head group, sugar fatty acid esters. 

Sugar fatty acid esters have been reviewed as a subclass of the more general sugar-based surfactants on a number of occasions. A very recent issue... 

Perhaps the most extensive area of research for sugar fatty acid esters is formulation of microemulsion systems. The potential applicability of these low-toxicity surfactants in the areas of cosmetics and food products has been the principle driving force for this research. 

Garti et al. have studied extensively the growing potential for microemulsions based on sugar fatty acid esters for utility in food products and have published a fairly recent review on the subject [94]. Since that review their work has continued in this important area of application for these materials, with a number of publications in the past 3 years. 

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