No abstract

27The effect of an additive on enzyme stability use to be considered an intrinsic feature of 28 the lipase. However, in this paper we have found that the effect of additive on enzyme stability 29 is depended on the immobilization protocol. After assaying the effects of diverse chloride salts 30 with different cations on different lipases activity, no relevant effect was detected. Free enzymes 31 or the covalently immobilized enzymes are not stabilized by these cations for any of the studied 32 lipases. However, Mn 2+ and Ca 2+ (at a concentration of 5 mM) are able to greatly stabilize the 33 lipases from Rhizomucor miehei (RML) and Candida rugosa (CRL) when they are present 34 during the inactivation, but only if the enzymes are immobilized on octyl-agarose (stabilization 35 factor ranging from 20 to 50). The effect was only detected using more than 2.5 mM of the 36 cations, and reached the maximum value at 5 mM, suggesting a saturation mechanism of action. 37The stabilization seemed to be based on a specific mechanism, and required to have the 38 recognition sites saturated by the cations. Mg 2+ has no effect on enzyme stability for both 39 enzymes, but it is able to suppress the stabilization promoted by the other two cations using 40 CRL; while it has no effect on the cation stabilization when using RML. 41 This is the first report of a cation induced enzyme stabilization effect that depends on the 42 lipase immobilization protocol. 43 44