Free Access
Volume 80, Number 1, January-February 2000
New applications of membrane technology in the dairy industry
Page(s) 197 - 203
DOI: 10.1051/lait:2000119

Lait 80 (2000) 197-203

Selective extraction of lysozyme from a mixture with lactoferrin by ultrafiltration. Role of the physico-chemical environment

Bernard Chaufer ${^{\rm a}}$, Murielle Rabiller-Baudry ${^{\rm a}}$, David Lucas ${^{\rm a}}$,
Françoise Michel ${^{\rm b}}$, Martin Timmer ${^{\rm c}}$

${^{\rm a}}$Laboratoire des procédés de séparation, UA 991 Université Rennes-I, INRA, Campus de Beaulieu Bât. 10A, CS 74205, 35042 Rennes Cedex, France
${^{\rm b}}$Laboratoire de recherches de technologie laitière, INRA, 65 rue de Saint-Brieuc, 35042 Rennes Cedex, France
${^{\rm c}}$Department of process engineering, NIZO, P.O. box 20, 6710 BA Ede, the Netherlands. present adress: Timmer technology development and consultancy, Bospoort 11A, 6711 BT EDE, the Netherlands


Variation of the physico-chemical environment was used to optimize the selective extraction of lysozyme (14 300 g.mol-1) from a model protein mixture with lactoferrin (77 000 g.mol-1, in monomer form) by ultrafiltration (UF). The system protein-membrane-electrolyte was studied using electrokinetic measurements, in order to determine the charge of both free proteins and fouled membrane, depending on the physico-chemical environment (pH, ionic strength, chemical nature of added salts). This paper shows that, in order to achieve the extraction of a protein from a mixture, the following strategy can be used: the target protein recovered in the permeate has to be uncharged, whereas the retained protein has to be charged in order to exploit the electrostatic repulsion of the membrane partly fouled by the charged protein. This approach was successfully used to achieve the lysozyme/lactoferrin separation with a high selectivity (lysozyme transmission/lactoferrin transmission) using an anionic membrane of pore diameter close to 28 nm. The selectivity of the separation was studied according to the variation of the ionic strength, in the range 1 to 150 mmol.L-1, with either sodium chloride or potassium phosphate. Whereas selectivities were close to 20 in sodium chloride, they were always greater in potassium phosphate and increased up to 120.

ultrafiltration / protein / selectivity / electrophoretic mobility / specific adsorption

Correspondence and reprints: B. Chaufer

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