Repository logo

Browsing by Author "Valero, F."

Now showing 1 - 3 of 3
  • Batch operational stability of immobilized heterologous Rhizopus oryzae lipase during acidolysis of virgin olive oil with medium-chain fatty acids
    Publication . Nunes, Patrícia A.; Cabral, Paula Pires; Guillen, M.; Valero, F.; Ferreira Dias, S.
    Structured triacylglycerols containing medium-chain fatty acids (M) at positions sn-1,3 and long-chain fatty acids (L) at the sn-2 position (MLM type), were obtained by acidolysis of virgin olive oil with caprylic or capric acid, in solvent-free media, at 40 degrees C, catalyzed by a heterologous Rhizopus oryzae lipase (r-ROL) immobilized in Eupergir (R) C or in Lewatit VP OC 1600. The biocatalyst immobilized in Eupergit was reused in consecutive 23-h batches with rehydration of the biocatalyst between batches. A first-order deactivation was observed (half-life time, t(1/2) = 39.0 h for caprylic; t(1/2) = 54.3 h for capric acid). During acidolysis with capric acid catalyzed by r-ROL immobilized in Lewatit VP OC 1600, without rehydration, a first-order deactivation was observed (t(1/2) = 49.1 h); with rehydration, a considerable increase in stability was observed (t(1/2) = 234 h; Sadana's series-type inactivation kinetics model). (C) 2012 Elsevier B.V. All rights reserved.
    2012Journal article Restricted access Show more
  • Optimized production of MLM Triacylglycerols catalyzed by immobilized heterologous rhizopus oryzae lipase
    Publication . Nunes, Patrícia A.; Cabral, Paula Pires; Guillen, M.; Valero, F.; Dias, S. Ferreira
    Response surface methodology was used to model and optimize the acidolysis of virgin olive oil with caprylic (C8:0) or capric (C10:0) acids, aimed at the production of low caloric triacylglycerols (TAG) of MLM type, in solvent free media, catalyzed by the heterologous Rhizopus oryzae lipase (r-ROL) immobilized in Eupergit(A (R)) C. This lipase was produced in the methylotrophic yeast Pichia pastoris Mut(s) phenotype (experiments with C10:0) or a Mut(+) phenotype (experiments with C8:0), under different operational conditions. The r-ROL used in experiments with C10:0 presented a hydrolytic activity about 5 times of that presented by r-ROL used in acidolysis with C8:0. The experiments were carried out following a central composite rotatable design, as a function of the molar ratio (MR) medium chain fatty acid/TAG (1.6-4.4) and temperature (25-55 A degrees C). Convex surfaces described by second order polynomials as a function of MR and temperature were well fitted to fatty acid incorporation values. After 24-h reaction, the predicted maximum incorporation of caprylic (15.5 mol%) or capric (33.3 mol%) acids in olive oil occurs at 37 and 35 A degrees C, respectively, and at C8:0/TAG of 2.8:1 or C10:0/TAG of 3:1. These predicted optima were experimentally validated. Fermentation conditions used in r-ROL production highly affected hydrolytic activity and to a lesser extent interesterification activity.
    2012Journal article Restricted access Show more
  • Production of MLM-Type structured lipids catalyzed by immobilized heterologous rhizopus oryzae lipase
    Publication . Nunes, Patrícia A.; Cabral, Paula Pires; Guillen, M.; Valero, F.; Luna, D.; Dias, S. Ferreira
    This work aims to produce triacylglycerols (TAG) containing a medium-chain fatty acid (M) at positions sn-1,3 and a long-chain fatty acid (L) at sn-2 position, i.e. TAG of MLM type, by acidolysis of virgin olive oil with caprylic (C8:0) or capric (C10:0) acids, catalyzed by 1,3-selective Rhizopus oryzae heterologous lipase (rROL) immobilized in Eupergit (R) C and modified sepiolite. This lipase was produced by the methylotrophic yeast Pichia pastoris. Reactions were performed at 25 and 40 degrees C, for 24 h, either in solvent-free or in n-hexane media, at a molar ratio 1:2 (olive oil:free fatty acid). Higher incorporations of C8:0 (21.6 mol%) and C10:0 (34.8 mol%) into the TAG were attained in solvent-free media, at 40 degrees C, when rROL immobilized in Eupergit (R) C was used. In organic media, at 40 degrees C, only 15.9 and 14.1 mol%, incorporation of C8:0 or C10:0 were, respectively observed. Lower incorporations were attained for both acids (3.4-7.0 mol%) when native ROL (nROL) in both supports and rROL in modified sepiolite were used. rROL in Eupergit (R) C maintained its activity during the first four or three 23-h batches, respectively when C8:0 (half-life time, t(1/2) = 159 h) or C10:0 (t(1/2) = 136 h) were used, decreasing thereafter following a time delay model.
    2011Journal article Restricted access Show more