Antimicrobial activity of olive mill wastewaters (alpechin) and biotransformed olive oil mill wastewater

Olive oil extraction produces a great volume of residue. These olive mill wastes are known as alpechin. This wastewater is a powerful pollutant, resistant to degradation and presents a severe environmental problem related to its high organic content made up largely of simple phenolic compounds, that have been described as being both antimicrobial and phytotoxic. This paper reviews briefly the antimicrobial activity of olive mill wastewaters and provides evidence to show the potential of micro organisms (Bacillus pumilus) to reduce the phenol content of alpechin, and also that biotransformation depends on the dilution (v/v) of the alpechin. Furthermore, we sought to provide a real evaluation of the extent of alpechin biotransformation. This was achieved by means of an internal reference, i.e. in relative terms, the phenol content resulting from the biotransformation process. The phenol content was measured using HPLC techniques, and results were obtained showing that the bacterium had most effect in reducing the phenol content of alpechin at concentrations of between 40 and 100%. It was also observed that at concentrations of 80%, in addition to a slight reduction in total phenols, new phenolic compounds, not present in the original alpechin, were generated.