Antibacterial Peptides Produced by Alcalase from Cowpea Seed Proteins.

Cowpea seed protein hydrolysates (CPH) were output from cowpea seeds applying alcalase® from Bacillus licheniformis . CPH with an elevated level of hydrolysis was fractionated by size exclusion chromatography (SEC). Both CPH and SEC-portions showed to contain antimicrobial peptides (AMPs) as they inhibited both Gram-positive bacteria, such as Listeria monocytogenes LMG10470 (L. monocytogenes) , Listeria innocua . LMG11387 (L. innocua ), Staphylococcus aureus ATCC25923 (S.aureus ), and Streptococcus pyogenes ATCC19615 (St.pyogenes ), and Gram-negative bacteria, such as Klebsiella pnemoniae ATCC43816 ( K. pnemoniae ), Pseudomonas aeroginosa ATCC26853 ( P. aeroginosa), Escherichia coli ATCC25468) ( E.coli ) and Salmonella typhimurium ATCC14028 (S. typhimurium ).The data exhibited that both CPH and size exclusion chromatography-fraction 1 (SEC-F1) showed high antibacterial efficiency versus almost all the assessed bacteria. The MIC of the AMPs within SEC-F1 and CPHs were (25 µg/mL) against P. aeruginosa , E.coli and St. pyogenes . However, higher MICsof approximately 100-150 µg/mL showed for both CPHs and SEC-F1 against both S. aureus and L. innocua ; it was 50 µg/mL of CPH against S.aureus . The Electro-spray-ionization-mass-spectrometry (ESI-MS) of fraction (1) revealed 10 dipeptides with a molecular masses arranged from 184 Da to 364 Da and one Penta peptide with a molecular mass of approximately 659 Da inthe case of positive ions. While the negative ions showed 4 dipeptides with the molecular masses that arranged from 330 Da to 373 Da. Transmission electron microscope (TEM) demonstrated that the SEC-F1 induced changes in the bacterial cells affected. Thus, the results suggested that the hydrolysis of cowpea seed proteins by Alcalase is an uncomplicated appliance to intensify its antibacterial efficiency.