AGGREGATE FORMATION DURING HYDROLYSIS OF BETA-LACTOGLOBULIN WITH A GLU AND ASP SPECIFIC PROTEASE FROM BACILLUS-LICHENIFORMIS

The hydrolysis of isolated beta-lactoglobulin (9 and 70-200 mg/mL) by a Bacillus licheniformis protease was followed to assess whether aggre gates and gels, respectively, were formed during hydrolysis. Changes d uring hydrolysis were monitored by electrophoresis, dynamic light scat tering, and fluorescence and circular dichroism spectroscopy. Gelation was monitored by dynamic oscillation theology. Upon hydrolysis of a b eta-lactoglobulin preparation with the B. licheniformis protease aggre gates were formed and a soft gel resulted from only 70 mg/mL of beta-l actoglobulin. The aggregates consisted of a number of peptides with mo lecular weight ranging from 2000 to 6000 and pI from 5 to 8. As the ag gregates were solubilized in either SDS or urea or at extreme pH value s, it is proposed that noncovalent interactions, mainly electrostatic and hydrophobic, are major interacting forces. These kinds of aggregat es are thought to be important in protease-induced gelation of whey pr otein isolate solutions.