Lipase-catalyzed production of diglycerides using SC-CO2
Tutor / director / evaluatorLubary, Marta
Document typeMaster thesis (pre-Bologna period)
Rights accessRestricted access - confidentiality agreement
Diacylglycerols (DAG) are esters of glycerol where two of the hydroxyl groups of glycerol are esterified with fatty acids. DAG exists in two isomeric forms, 1,2(2,3)-DAG and 1,3-DAG, with a natural ratio of approximately 3:7. DAGbased edible fats or oils can be used as a substitute of natural triacylglycerolbased oils, because of their enhanced nutritional properties. In particular the 1,3-DAG isomer is beneficial. We developed a novel biocatalytic method for producing a fatty material rich in DAG in their natural ratio, using milk fat as the raw material and supercritical carbon dioxide (SC-CO2) as the only processing solvent. The process steps of the method are alcoholysis of the fat, separation by SC-CO2 extraction of the produced fatty acid esters from the DAG product, and induced acyl migration to increase the ratio 1,3-DAG/1,2(2,3)-DAG. The main advantages of this process over existing ones are that a high 1,3-DAG yield can be obtained, and that the mild process conditions used avoid possible degradation of the product. The alcoholysis of TAG from milk fat was carried out using an immobilized lipase from Pseudomonas fluorescens, a highly selective lipase able to produce 1,2-DAG as the main partial glyceride product. The influence of several reaction variables on lipase activity and selectivity were studied, including lipase load, temperature, solvent medium, pressure, reactants ratio and humidity of the lipase carrier. The lipase resulted to be selective towards long-chain fatty acids, being able to produce a partial glyceride product which retained the short-chain fatty acids. By extraction with SC-CO2, complete separation of fatty acid ethyl esters from the partial glyceride mixture was achieved. Induced acyl migration increased the 1,3-DAG yield, at 50ºC and presence of silica.
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