Aggregate formation during hydrolysis of beta-lactoglobulin with a glu and asp specific protease from Bacillus licheniformis.

摘要

The hydrolysis of isolated beta-lactoglobulin (9 and 70-200 mg/ml) by a B. licheniformis proteinase was studied to assess whether aggregates and gels, respectively, were formed during hydrolysis. Changes during hydrolysis were monitored by electrophoresis, dynamic light scattering and fluorescence and circular dichroism spectroscopy. Gelation was monitored by dynamic oscillation rheology. Upon hydrolysis of beta-lactoglobulin, aggregates were formed and a soft gel resulted from only 70 mg/ml of beta-lactoglobulin. The aggregates consisted of peptides with molecular weights ranging from 2000 to 6000 and isoelectric points from 5 to 8. As the aggregates were solubilized in SDS or urea or at extreme pH values, it is proposed that non-covalent interactions, mainly electrostatic and hydrophobic, are major interacting forces. These aggregates are important in proteinase-induced gelation of whey protein isolate solutions.