Bioactive peptides generated in an enzyme membrane reactor using Bacillus lentus alkaline peptidase

Bacillus lentus alkaline peptidase (BLAP) was used for casein (CN) hydrolysis in an enzyme membrane reactor (EMR) because it was found that BLAP was competitively inhibited by its products. The employed membranes had different molecular weight cut-offs (MWCO 1, 5 and 10 kDa). It was shown that the productivity of the EMR could be significantly improved (28 %) in comparison with batch hydrolysis under the same conditions after 20 h. All resulting EMR peptide mixtures showed a homogenous peptide pattern in HPLC-UV analysis. The obtained peptide mixtures exhibited Angiotensin-I-converting enzyme (ACE) inhibitory and antioxidative activity. The ACE inhibition of the peptide mixtures was dependent on the MWCO of the membranes. The resulting apparent IC50 values were 115, 131 and 420 mu g ml(-1) for the 1, 5 and 10 kDa MWCO membranes, respectively. In kinetic studies, a mixed-type inhibition was observed for the three peptide mixtures. The radical scavenging activity was determined with the ABTS assay, and IC50 values between 20 and 25 mu g ml(-1) were obtained for the generated peptide mixtures. In addition, the identified VYPFPGPIPN peptide exhibited ACE inhibition and antioxidant activity with IC50 values of 325 and 6.2 mu M, respectively. The peptide YQEPVLGPVRGPFPIIV exhibited radical scavenging activity with an IC50 value of 5.2 mu M.