Study On Bioactive Peptides Prepared By Enzymolysis Of Pea Protein Isolate

Biologically active peptides which were produced by enzymolysis of plant proteins canbe applied in the fields of food, medicine and cosmetics.In this study, pea protein isolate was used as raw material to prepare antibacterial peptidesand antioxidant peptides by enzymolysis. The active components were separated andcharacterized. Their potential in application is also discussed.Using single protease (neutral protease, alkaline protease, trypsin and papain), theenzymatic hydrolysis conditions of pea proteins were optimized by single factor experimentwith the degree of hydrolysis (DH) as indexes. Under optimum conditions, the DH of tryptichydrolyzate was the highest. The molecular weight distribution of various hydrolysates wasanalyzed by gel filtration chromatography.Using Staphylococcus aureus as indicator, papain was chosen as hydrolyzing enzymeaccording to the antibacterial ability of various hydrolysates. The optimal hydrolysisconditions are: pH6.5, substrate concentration5%(w/v), enzyme/substrate2.5%(w/w),hydrolysis temperature65℃, hydrolysis time2h. Under this condition, the hydrolyzateshowed a relatively broad spectrum of antibacterial activity. The antibacterial peptides werepurified through sequential use of alcohol precipitation, DEAE-52ion exchangechromatography, SuperdexTMpeptide10/300GL gel filtration chromatography, and ResourceQ ion exchange chromatography. The molecular weight of antibacterial peptides is distributedwithin1.9~3.7kDa. The results showed that the minimum inhibitory concentration of theantibacterial peptides towards S. aureus is0.25mg/mL. The antibacterial effect of peaantibacterial peptides at the concentration of10mg/mL equals to10.72U/mL of kanamycinor2.08U/mL of gentamicin. It exhibits high thermal stability.By employing DPPH as indicator, the antioxidant activity of various hydrolysate wasaccessed, and neutral protease combined with trypsin was screened to prepare pea proteinhydrolysate (PPH). The concentration of PPH required to scavenge50%of DPPH radicals(IC50) is3.01mg/mL. Antioxidant peptides were isolated by gel filtration chromatography onSephadex G-25and reversed phase chromatography on RESOURCETM3RPC. The purity ofantioxidant peptides was analyzed by RP-HPLC. The DPPH radicals scavenging activity ofthe purified peptide could reach62.03%at the concentration of0.2mg/mL, close to that ofglutathione (66.82%). The molecular mass of the antioxidant peptide is956.5Da and itsamino acid sequence was identified as Phe-Glu-Gly-Met-Thr-Phe-Leu-Leu by Q-TOF-MS.Nanofiltration was used in effective desalting of PPH. The total desalting ratio was79.87%and PPH was concentrated2.86times. Then pea antioxidant peptides were added intomoisturizers with varying concentration, tests showed that it has good stability andantioxidant ability. Therefore it would have potential applications in functional cosmetics.