An environmentally benign and volume efficient process for enzymatic production of alkanolamides is described. Immobilized Candida antarctica lipase B, Novozym435, was used to catalyze the condensation of lauric acid with monoethanolamine. The reaction temperature of 90 degrees C was required to keep the reactants in a liquid state. Stepwise addition of the amine minimized problems caused by the formation of a highly viscous amine/fatty acid ion-pair. The enzyme was both very active and stable under the reaction conditions, with about half of the activity remaining after 2 weeks. The maximum amide yield obtained when using equimolar amounts of the reactants was 75%, which could be increased to 95% upon water removal. Special precautions to avoid co-distillation of the amine were required. Two different strategies to avoid the amine loss are presented.
N,N-di(3-aminopropyl)dodecylamine (C12-Y-amine), N-dodecyl-N,N-di[(3-D-gluconylamido)propyl] amine (C12-DGA), N-dodecyl-N,N-bis[(3-lactobionylamido)propyl]amine (C12-DLA), N-dodecyl-N-[(3-lactobionylamido)propyl]amine (C12-LA), and ethoxylated N,N-di(3-aminopropyl)dodecylamine [C12-Y-amine with 4 and 8 ethylene oxide (EO)] have been synthesized,and their physical-chemical properties have been studied. Adsorption was measured at the air-water interface by the du Noü y ring method and at solid surfaces consisting of self-assembled monolayers (SAMs) of alkanethiols on gold using surface plasmon resonance. Results from surface tension measurements showed that adsorption at the air-water interface is pH dependent. At low pH, reduction in surface tension is less pronounced as a result of protonation of the amino groups of the surfactants. At the SAM model surfaces, generated by adsorption of alkanethiols or mixtures of alkanethiols on gold presenting methyl, hydroxyl, and carboxyl groups, the highest amount of adsorbed surfactant was obtained on a surface composed of a mixture of methyl and carboxyl groups. In general, the sugar-derived surfactants, DGA, DLA, and LA, adsorbed less than the ethoxylates. Surfactant biodegradation was investigated by the closed bottle test.Only C12-Y-amine was found to be readily biodegradable. However, the polyol surfactants were more biodegradable than the ethoxylates.
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