Studies on lipase-affinity adsorption using response-surface analysis

Lipases are widely distributed enzymes that can be obtained from animals, p lants and micro-organisms. Coupling lipases with a wide range of substrates allows the opportunity for synthesis of optically pure pharmaceutical prep arations, flavour compounds and other food additives. Affinity chromatograp hy owes its power as a purification method to specific biological interacti ons. Response-surface analysis was chosen to study column efficiency. This method allows the understanding of interactions between variables with adva ntages over conventional methods, which involve changing one variable while fixing others at certain levels. The aim of this work was to study the inf luence of the ratio bed height/column diameter (L/D) and superficial veloci ty (V) on the column efficiency. The experimental design involved the two v ariables, Un (2-10) and v (1-2 cm/min), at five levels. Lipase was obtained from Geotrichum sp, culture in a complex medium composed of 5% corn-steep liquor, 0.5% NH4NO3 and 1% alive oil at 30 degreesC, with I VVM (air volume /medium volume per min) aeration and 400 rev,/min agitation. Maximum lipase activity was 19 units/ml after almost 9h of fermentation. This lipase coul d potentially be used in esterification reactions to increase the content o f gamma -linolenic acid and to produce bioaromas for food industries. The a dsorption assays were carried out in a fixed-bed column with an affinity ad sorbent, which was obtained by reaction of a gel with oleic acid as ligand, Breakthrough curves were obtained for all experiments. It has been shown t hat the lower the values of both Un and v, the higher the column efficiency (maximum 65.43%), Also, it was observed from the response surface that the efficiency reached a minimum at an L/D of around 8.