Abstract
This study investigates the effect of different concentrations (0.50 to 1.50%) of thermo-chemically modified lysozyme on the growth of selected bacteria, that is, Gram-negative Pseudomonas fragi, Pseudomonas fluorescens, Escherichia coli, Proteus mirabilis and Gram-positive Listeria innocua, Leuconostoc mesenteroides in nutrient broth. The content of lysozyme polymeric forms after modification was evaluated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The dimer and trimer fractions of the modified lysozyme were 35.9 and 33.1%, respectively. The modified lysozyme exhibited higher surface hydrophobicity and lower hydrolytic activity than monomer. No inhibitory action of lysozyme monomer was observed in relation to the tested Gram-negative bacterial strains. The application of modified lysozyme at a concentration of 0.75% and higher, caused a complete reduction of bacterial counts as early as after 1 h incubation in case of P. fragi, P. fluorescens and E. coli or after 6 h incubation in case of P. mirabilis. After 6 h incubation both in samples with an addition of monomer and those with modified lysozyme a complete growth inhibition of L. mesenteroides was recorded. Modified lysozyme showed a stronger antibacterial activity against L. innocua than native lysozyme. Conducted analyses indicate that changes in the structure of enzyme molecules leads to an increase in the antibacterial action mainly towards Gram-negative bacteria. Key words: Antibacterial activity, modified lysozyme.
Highlights
Lysozyme is an enzyme commonly found in various biological fluids and tissues
This study investigates the effect of different concentrations (0.50 to 1.50%) of thermo-chemically modified lysozyme on the growth of selected bacteria, that is, Gram-negative Pseudomonas fragi, Pseudomonas fluorescens, Escherichia coli, Proteus mirabilis and Gram-positive Listeria innocua, Leuconostoc mesenteroides in nutrient broth
Conducted analyses indicate that changes in the structure of enzyme molecules leads to an increase in the antibacterial action mainly towards Gram-negative bacteria
Summary
Lysozyme is an enzyme commonly found in various biological fluids and tissues. Egg white is a rich and readily available source of lysozyme containing from 0.3 to 0.4 g enzyme per egg. Antibacterial action of lysozyme concerns first of all Gram-positive bacteria and is primarily ascribed to its hydrolase enzyme activity. It seems essential to search for strategies facilitating an extension of the antibacterial spectrum of the enzyme action Such a possibility is provided by a modification of lysozyme by covalent attachment of fatty acids, poly-saccharides, Cterminal hydrophobic peptides and the use EDTA or polycations. Analyses indicate that an increase in the antibacterial action may be provided applying thermal, thermo-chemical or membrane modification. Action of such modified enzyme is not dependent on hydrolytic activity, but on a novel, still not completely defined action (Ibrahim et al, 1996a; Leśnierowski, 2007)
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