Preparation and characterization of antimicrobial cationized peptides from barley (Hordeum vulgare L.) proteins

- Barley protein was hydrolyzed and fractionated to obtain large Mw fraction.
- Cationized peptides possessed high positive charges even at neutral pH.
- Cationized peptides can effectively prevent the growth of non-beneficial bacteria.
- Lower antimicrobial activity was observed against beneficial lactic acid bacteria.
- Flexible structure and positive charge promote peptide interaction with bacterial membrane.

In the current study barley protein hydrolysate was cationized using polyethyleneimine and the physicochemical and antimicrobial properties of the modified peptides were investigated. Degree of substitution and zeta potential analysis verified the high proportion of positively charged components. Antimicrobial assay showed that cationized peptides effectively inhibited non-beneficial bacterial growth (Escherichia coli JM109 and Micrococcus luteus (ATCC 4698)) at low concentration (98-195 μg/mL), while higher concentration levels (390-1560 μg/mL) were required to inhibit the growth of beneficial lactic acid bacteria (Lactobacillus reuteri (ATCC 23272) and Lactococcus lactis MG 1363). Structural studies revealed the unordered open structures as the major structural elements of cationized peptides which resulted in conformational flexibility. Highly exposed hydrophobic segments accompanied by the chain flexibility could positively contribute to adsorption and penetration of cationized peptides into bacterial membrane. These unique structural characteristics of barley proteins in combination with positively charged side chains confer potential antimicrobial activity to barley-derived peptides which can be applied to enhance the shelf life stability of food, feed and other products.