Charged fusions for enhanced protein purification and immobilization by ion exchange.

摘要

This work was undertaken to investigate the enhanced binding of genetically engineered ;The potential end use advantages of the fusions for immobilization was studied using flat sheet ion-exchange membranes. The added tails did not interfere with the kinetic behavior for lactose hydrolysis. The enhanced binding of BGCD11 on the membrane enabled the enzyme to hydrolyze acid whey permeate at 0.3 M ionic strength without leakage. An intregated separation and immobilization scheme was illustrated by the development of an immobilized enzyme reactor directly from cell extract.;The protein retention behavior was investigated using high performance liquid chromatography with perfusion packings. The added tails promoted retention which increased with the tail length (charge) and were best utilized closer to the isoelectric point. The two parameters, Z and I, obtained from the stoichiometric displacement model were used to characterize the protein interaction with the ion-exchange surface. At pH 5.7, the Z number increased with tail length (charge) and was 11.5, 8.5, 6.9 and 5.3 for BGCD11, BGCD5, BGCD1 and BGWT, respectively. At these conditions, the fusions had very similar I values which were five times smaller than those of BGWT. However, the increase in Z numbers outweighed the decrease in I values and an overall enhanced retention was reported. When BGWT was brought to the same net charge (by increasing the mobile phase pH) as each of the fusions, the Z number was similar to that of the corresponding fusion. However, the I values decreased with increasing pH (net charge) and were lower than that of the corresponding fusion. Consequently, despite the similar Z numbers, the fusions had a higher retention.;The use of charged fusions for selective protein recovery was studied using hollow fiber ion-exchange membranes. The added tails allowed selective binding and release of