Journal article
Study of the solubility of a modified Bacillus licheniformis alpha-amylase around the isoelectric point
Center for Microbial Biotechnology, Department of Systems Biology, Technical University of Denmark1
Department of Systems Biology, Technical University of Denmark2
Center for Phase Equilibria and Separation Processes, Department of Chemical and Biochemical Engineering, Technical University of Denmark3
Department of Chemical and Biochemical Engineering, Technical University of Denmark4
Center for Energy Resources Engineering, Centers, Technical University of Denmark5
The solubility of a modified recombinant Bacillus licheniformis alpha-amylase (mBLA) has been studied by batch crystallization. A semi-pure preparation was chosen containing five isoforms with pI values from 6 to 7.3 (weighted average of 6.6). Small amounts (<1 %) of protein impurities were also present.
Solubility was studied in the pH range of 6 to 8. The lowest solubility without added salts was 60 mg.mL(-1) at pH 7. The addition of 0.1 mol.L-1 sodium salts of nitrate, sulfate, and thiocyanate had a small effect on solubility. However, solubility was lowered significantly by adding 0.5 mol.L-1 sodium sulfate at all pH values and increased with 0.5 mol.L-1 sodium thiocyanate at pH 7 and pH 8.
The effect of anions on alpha-amylase solubility followed the Hofmeister series, and only weak evidence of reversal was seen below the isoelectric point. Cations had little effect on solubility. The sign and magnitude of the alpha-amylase zeta potential was determined in the presence and absence of 0.1 mol.L-1 salt.
Qualitatively, zeta potential correctly predicted the different salts influence on mBLA solubility.
Language: | English |
---|---|
Year: | 2007 |
Pages: | 707-713 |
ISSN: | 15205134 and 00219568 |
Types: | Journal article |
DOI: | 10.1021/je0603123 |
ORCIDs: | Hobley, Timothy John |