Surfactants based on natural products - enzymatic synthesis and functional characterization
Abstract: Surfactants are molecules that contain a water-soluble and afat-soluble part. They have important functions in productssuch as detergents, cosmetics, pharmaceuticals and foods aswell as in many industrial processes. Surfactants are used onvery large scale, which makes it important to decrease theirimpact on the environment. This can be done by starting withnatural materials, by improving the synthetic methods and byreducing the use of limited resources such as energy andorganic solvents.This thesis focuses on lipase-catalyzed synthesis ofsurfactants based on natural products. It also includesfunctional studies of the produced surfactants; as antioxidantsin oils, or as surfactants to solubilize pharmaceuticals.Unsaturated fatty acid esters of ascorbic acid weresynthesized with catalysis by Candida antarctica lipase B int-amyl alcohol and in ionic liquids. High yields ofascorbyl oleate were obtained in an ionic liquid that wasdesigned to improve the solubility of the fatty acid, when thereaction was performed under vacuum. Ascorbyl oleate wasamorphous and was a better antioxidant than ascorbyl palmitatein rapeseed oil.Polyethylene glycol (PEG) stearate, PEG 12-hydroxystearateand a series of PEG 12-acyloxy-stearates were synthesized in avacuum-driven, solvent-free system usingC. antarcticalipase B as catalyst. Critical micelleconcentration and solubilization capacity were determined forthe PEG 12-acyloxy-stearates. Their effects on living cellswere evaluated in studies of hemolysis and transepithelialelectrical resistance. Several PEG1500 12-acyloxy-stearateswere excellent solubilizers for pharmaceutical use and hadnegligible negative effects on living cells even at highconcentrations.Enzymatic and chemo-enzymatic methods offer uniquepossibilities to synthesize surfactants of high purity. Pureand well-defined surfactants enable new applications and areimportant for the understanding of surfactantstructure-function relationships.
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