Lysozyme extraction from egg white using reverse micelles in a Graesser contactor: mass transfer characterization.

Abstract

The gentle mixing characteristics of a Graesser contactor can help to avoid the formation of stable emulsions, which is one advantage of this type of contactor when used with reversed micellar extraction. In this study, the performance of the Graesser contactor in lysozyme extraction from hen egg white is investigated. The concentration profile of lysozyme in the aqueous and organic phases indicated that, while substantial axial mixing occurred in the contactor, the extraction yield was in the range of 97% to 99%. The number of mass transfer units (N(ox)) was determined using a diffusion model, and the influence of aqueous-to-organic phase flow ratio, rotor speed, and total throughput on contactor performance was studied. It was found that the diffusion model could describe quite well the extraction of lysozyme from hen egg white using reversed micelles. The optimal conditions for the extraction at steady state were found to be a rotor speed of 5 rpm, an aqueous-to-organic phase flow ratio of 60:20 mL/min, and a total throughput of 80 mL/min. In addition, back-extraction was also performed using the conventional method (1.5 M KBr at pH 11.5) in the contactor. It was found that this mass transfer was not well described by a diffusion model, although 85% of the lysozyme could be recovered with the operating conditions used: a rotor speed of 10 rpm, and an aqueous-to-organic flow rate of 10:10 mL/min.