Antimicrobial activity of native and esterified legume proteins against Gram-negative and Gram-positive bacteria
2010
Sitohy, Mahmoud | Osman M. Ali Gurey.
Three legume proteins (broad bean, soybean and chick pea proteins) were isolated and esterified with methanol in the presence of hydrochloric acid (50mol acid/mole carboxylic group) for 10h at 4°C to give yields of 75%, 80% and 83%, respectively. The SDS-PAGE molecular weight distribution of proteins showed slight increments after esterification. Esterification raised the pIs (iso-electric points) of legume proteins from pH 4.5 for the native legume proteins, to pH 6 in the case of broad bean protein and pH 8 in the case of soybean and chick pea proteins. Applying methylated proteins at three different concentrations (0.1, 1.0 and 10mg/ml) to Petri dishes containing nutrient agar infected with two pathogenic Gram-positive (Bacillus subtilis and Staphylococcus aureus) and two Gram-negative bacteria (Pseudomonas aeroginosa and Escherichia coli) gave rise to concentration-dependent inhibition zones. Applying native or methylated proteins at low or medium concentrations (0.1% and 0.5%) to 100ml nutrient broth infected with 200μl of either Gram-positive or Gram-negative bacteria resulted in lower media turbidity (OD₆₀₀) values, when compared to control and referring to lower bacterial growth.
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