Optimisation of isolation and purification of the jack bean enzyme urease by extraction and subsequent crystallization.

摘要

This study investigated the extraction and purification by crystallization of urease from jack bean meal, with a view to developing a large-scale process. Effects of various extraction solvents and additives on crystal size, protein yield and protein purity were evaluated. Urease enzymic activity was used as a measure of the amounts and purity of the protein obtained. Almost all of the protein was obtained in a single extraction step. Subsequent extraction stages, using the same jack bean meal, but fresh solvent, yielded only small additional amounts of protein; <10 and <3% of total protein were extracted in second and third steps, respectively. Product quality varied with the solvent used, but no single solvent led to optimization of all quality criteria. Furthermore, the point at which the acetone precipitant was introduced into the process had an impact on product quality. Judicious choice of extraction conditions could significantly increase urease crystal size at the expense of product purity, according to specific activity values. On the other hand, smaller crystals could be obtained with a high degree of product purity (max. 138-x increase in purity), with a max. yield of 8.4%.