Production of functional peptides from livestock and fish waste

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A procedure for the production of functional food from livestock and fish waste such as bone, skin, and sea bream scales containing collagen was developed. Sixteen commercial enzymes were selected to evaluate their effectiveness for degradation of the waste containing collagen. The hydrolysates had a high anti-radical activity (IPOX_<50>, 0.18 and 0.45 mg/ml) and a high potential for decreasing blood pressure (IC_<50>, 0.46 and 0.71 mg/ml). The hydrolysate from sea bream scales, of which IC50 was 0.57 mg/ml was further studied. Using spontaneously hypertensive rats, oral administration of 300 mg of the peptides/(kg of body weight)/d was shown to significantly (p<0.05) decrease blood pressure. Four peptides that demonstrated high angiotensin I converting enzyme (ACE) inhibitory activities were isolated from the hydrolysate of the scales using chromatographic methods using gel filtration chromatography (Sephadex LH-20), anion-exchange chromatography (UNO Q-1), gel filtration chromatography (Superdex Peptide HR 10/30), and reverse-phase chromatography (Sephasil Peptide C18 column). The ACE inhibitory activities of the four peptides isolated by reverse-phase chromatography were 5 to 20 times higher than that of the unpurified hydrolysate. The amino acid sequences of inhibitory peptides ware determined to Gly-Tyr, Val-Tyr, Gly-Phe and Val-Ile-Tyr; furthermore, synthetic Val-Ile-Tyr and Val-Tyr demonstrated high ACE inhibitory activities with IC_<50> values of 7.5 μM and 16 μM, respectively. The C-terminal amino acid of the peptides, that is most important contribution to substrate binding at the ACE active site, were tyrosine and phenylalanine.