Bioactive peptides from caseins released by cold active proteolytic enzymes from Arsukibacterium ikkense

Proteolytic enzymes secreted by the cold-adapted microorganism Arsukibacterium ikkense were tested for their ability to degrade caseins at low temperature and produce bioactive peptides. The caseins were extensively degraded (90%) after 24 h of hydrolysis at 5 °C and completely degraded at 25 °C, and many novel peptides were formed. The most hydrolysed sample showed high angiotensin I converting enzyme (ACE)-inhibitory and antioxidant activity, and a number of potent ACE-inhibitory and antioxidant peptides were identified. The presence of tyrosine seemed fundamental for both ACE-inhibitory and antioxidant activity, while phenylalanine seemed to potentiate the antioxidant activity. The novel peptide YPELF was found to have strong radical scavenging and lipid oxidation inhibitory activities, with IC50 for both around 3.5 μM. None of the hydrolysates showed antimicrobial activity. Secreted enzymes from cultures of A. ikkense could thus be a valuable enzyme preparation for inexpensive, energy-efficient production of potent bioactive peptides from caseins in milk at low temperatures.