Abstract

The aim of this study was to investigate the effect of different concentrations of ethanolic extract of propolis (EEP) on oxygen consumption and vitality of gram-positive, Gram-negative bacteria, and yeast. Our investigations showed that EEP at the concentration of 65 - 1,300 mg ml^-1 of phenolic compounds (PC) inhibited oxygen consumption rate of Bacillus subtilis by 26 - 81%, and ofCandida albicans - by 6 - 70%, and significantly decreased cell count of the investigated Gram-positive bacteria (Bacillus cereus, B. subtilis) and yeast. EEP at the concentration of 260 - 2,340 mg ml^-1 of PC inhibited oxygen consumption rate of Escherichia coli by 6 - 54%, and reduced cell count of Gram-negative bacteria (Salmonella typhimurium, E. coli). Positive linear correlations (r² - 0.97, 0.98, and 0.89 with B. subtilis, C. albicans and E. coli, respectively) were revealed between the inhibition of oxygen consumption and vitality of the investigated microorganisms. Therefore, it is believed that EEP inhibition of oxygen consumption decreases the vitality of microorganisms, and it could be one of the reasons for the antimicrobial action of propolis.

Key words: Ethanolic extract of propolis, phenolic compounds, microbial oxygen consumption, microbial vitality.