Peptides with improved antimicrobial activity screened by membrane ultrafiltration from egg white protein hydrolysates

Abstract

This contribution was aimed at the fractionation and identification of peptides with improved antimicrobial activity from egg white protein hydrolysates, obtained by membrane ultrafiltration. For this purpose, the thermal treated egg white proteins were intensively hydrolysed with a commercial food-grade bacterial endopeptidase from Bacillus licheniformis, namely Alcalase. Thus, obtained hydrolysates were further separated by sequential ultrafiltration into four peptide fractions viz. fraction I (> 30kDa), II (10 - 30 kDa), III (1 - 10 kDa) and IV (< 1kDa) which were investigated in terms of their antimicrobial activity. The antimicrobial activity was tested against Gram-positive bacteria (Staphylococcus aureus ATCC 25923), Gram-negative bacteria (Escherichia coli ATCC 25922) and against yeast Candida albicans (ATCC 24433) by fractions' susceptibility of agar diffusion. Our results showed that these peptide fractions have an intense inhibitory activity on Gram-positive bacteria, poor on Gram-negative bacteria and none inhibitory activity on growth of C. albicans. The results showed interesting antimicrobial potentials versus the tested microorganisms, especially fractions with peptides molecular weight of 10-30 kDa and 1-10 kDa. It can be concluded, that the controlled enzymatic hydrolysis of egg white proteins and their subsequent membrane ultrafiltration is considered to be a suitable way for production of biocative peptides with exhibit antimicrobial efficiency.