Synergistic Antibacterial Effects of Polyphenolic Compounds from Olive Mill Wastewater

Ahmed Tafesh,Jeries Jadoun,Herbert Riepl,Hassan Azaizeh,Naim Najami,Fares Halahlih

doi:10.1155/2011/431021

Abstract

Polyphenols or phenolic compounds are groups of secondary metabolites widely distributed in plants and found in olive mill wastewater (OMW). Phenolic compounds as well as OMW extracts were evaluated in vitro for their antimicrobial activity against Gram-positive (Streptococcus pyogenes and Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli and Klebsiella pneumoniae). Most of the tested phenols were not effective against the four bacterial strains when tested as single compounds at concentrations of up to 1000 μg mL−1. Hydroxytyrosol at 400 μg mL−1 caused complete growth inhibition of the four strains. Gallic acid was effective at 200, and 400 μg mL−1 against S. aureus, and S. pyogenes, respectively, but not against the gram negative bacteria. An OMW fraction called AntiSolvent was obtained after the addition of ethanol to the crude OMW. HPLC analysis of AntiSolvent fraction revealed that this fraction contains mainly hydroxytyrosol (10.3%), verbascoside (7.4%), and tyrosol (2.6%). The combinations of AntiSolvent/gallic acid were tested using the low minimal inhibitory concentrations which revealed that 50/100–100/100 μg mL−1 caused complete growth inhibition of the four strains. These results suggest that OMW specific fractions augmented with natural phenolic ingredients may be utilized as a source of bioactive compounds to control pathogenic bacteria.

Highlights

The process of olive oil production is accompanied by generation of a considerable amount of olive mill wastewater (OMW)
These results suggest that OMW specific fractions augmented with natural phenolic ingredients may be utilized as a source of bioactive compounds to control pathogenic bacteria
Studies have been focused on antimicrobial agents and on the antimicrobial properties of plant-derived active principles [10, 16, 26, 37]

Summary

Introduction

The process of olive oil production is accompanied by generation of a considerable amount of olive mill wastewater (OMW). Up to 30 million m3 of OMW is produced annually in the Middle Eastern countries during the olive oil processing. The OMW is rich with organic compounds (mainly phenols) which creates a number of acute environmental and ecological problems [1, 2]. There is no accepted treatment method for all the wastes generated during olive oil production [3]. The phenolic fraction of olive oil comprises only 2% of the total phenolic content of the olive fruits, with the remaining 98% being lost in olive mill waste (OMW) [8]. OMW is potentially a rich source of a diverse range of phenols with a wide array of biological activities.

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