Forced Convection Evaporation for Bulk Protein Crystallization

Abstract

Forced convection evaporation was adopted for bulk protein crystallization. As a model system ovalbumin in aqueous solutions of ammonium sulfate was used. The crystallization process was performed in a drying chamber, where the protein solution was contacted with a warm air stream at a temperature varied from 35 to 52 °C. The slow evaporation of water induced gradual crystallization of the protein. Heat and mass transfer in the water−air system during water evaporation caused the temperature of the protein solution to remain distinctly below the air temperature. This allowed processing the protein under mild conditions. The process design was guided by crystallization phase diagram and kinetic measurements. The supersaturation degree, which determines the nucleation and crystal growth rates, was adjusted by the rate of water evaporation. The latter was precisely controlled by matching the temperature in the chamber to the air humidity. The process could be accomplished in a single crystallization stage in 50−95 min, with the protein yield of 72−85%. Ovalbumin appeared as clusters of irregular crystals; no amorphous precipitate was formed. An increase in the evaporation rate caused the crystal size to increase.

Production of Cross-Linked Lipase Crystals at a Preparative Scale

“…59 They also reviewed the most recent uses of crystallization as a purification step. A number of different strategies are being assayed from the combination of a stirred tank with a cooled tubular reactor in bypass, 60 the force convection evaporation, 61 continuous flow, 62,63 or even an airlift, 64 among several others recently reviewed. 65 In this work, we demonstrate how crystallization can solve several issues at the industrial level for the use of protein crystals.…”