Biological treatment of olive mill wastewater by non- conventional yeasts

The ability of lipolytic yeast strains to grow on Olive Mill Wastewater (OMW) based medium and to produce high-value compounds while degrading this waste, was tested. OMW collected from 3-phase olive mills from the North region of Portugal were used and characterized. OMW with COD ranging from 100 g L^-1 to 200 g L^-1 were supplemented with yeast extract and ammonium chloride. Studies of OMW consumption were carried out in batch cultures of Candida rugosa, Candida cylindracea and Yarrowia lipolytica. All strains were able to grow in the OMW based media, without dilution, to consume reducing sugars and COD. C. cylindracea was the best strain concerning the lipase production and the reduction of phenolic compounds and COD. The phenols degradation, for all strains, was quite difficult, mostly when more easily degradable carbon source is still present in the medium. Among the phenolic compounds tested catechol is the inhibitoriest to the cells.