A biotechnological valorization and treatment of olive mill waste waters by selected yeast strains

Olive mill waste waters were diluted to 1/10, supplied with 2% urea and inoculated with yeast strains. 20 yeast strains isolated from Olive Mill Waste (OMW) water were screened for their biomass production, COD reduction and polyphenols bioconversion activities. Pure cultures of yeasts were realized in 100 ml erlen-meyer flasks. 50 ml cultures were used and the flasks were incubated at room temperature (22 degrees C) on a shaker. Biomass production, COD (chemical oxygen demand) reduction and Polyphenols bioconversion were followed up in the inoculated OMW waters. Results showed that the urea supply improve significantly the biomass production relatively to the control. This reached in some assays 2.06% expressed as g of biomass dry weight per 100 mL of OMW water. Polyphenols removal was estimated to around 50% and the COD was decreased from 54.14 g/Kg to 21.56 g/Kg. This aerobic treatment lead to the biomass production and also to a pretreated efluent by the COD and the removal of the methanization inhibiting polyphenolic compounds.