Solvent-freeze-out (SFO) technology: A controlled crystallization process—Case study of jack bean urease

• Solvent freeze out (SFO) technique is used in a “real” protein mixture.
• A satisfactory purity and a decent yield of urease are obtained using the SFO.
• The enzymatic activity is also preserved after the SFO process.
• The quality of ice layer is the key for controlling the crystallization process.

The solvent freeze out (SFO) technique is here the first time introduced and used to purify a realistic and complex protein mixture. Urease crystals were obtained from jack bean meal in the process and the purity of which were evaluated via both specific activity and SDS-PAGE. Compared to a conventional salting out crystallization, the use of SFO technology can provide a better control of the crystallization process. A detailed investigation into the crystallization process is presented by carrying out experiments with different parameters. Results showed that the quality of the ice layer is the key factor for the control of the crystallization process. The SFO technology can be considered a promising alternative in protein crystallization, because the process itself is efficient and reproducible. Even though not fully optimized, a satisfactory product purity and a decent yield of urease crystals were obtained using the SFO technology. The enzymatic activity was also preserved after the SFO process in the here carried out case study.

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