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

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 p erformance of the Graesser contactor in lysozyme extraction from hen egg wh ite is investigated. The concentration profile of lysozyme in the aqueous a nd organic phases indicated that, while substantial axial mixing occurred i n the contactor, the extraction yield was in the range of 97% to 99%. The n umber 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 t he diffusion model could describe quite well the extraction of lysozyme fro m hen egg white using reversed micelles. The optimal conditions for the ext raction 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 conventio nal 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. (C) 2000 John Wiley & Sons, Inc.