Olive mill wastewater biological assessment: optimization and identification of compounds degrading yeasts

The present work aims to evaluate the capacity of a yeast strain to degrade the olive mill wastewater (OMWW) and to obtain a stabilized product that can be disposed without any environmental impact on the water-soil-plant system. The pollutant load, expressed by the chemical oxygen demand (COD) and the phenolic compounds (PC), are 187.63 and 4.30 g/L, respectively. The evaluation of the yeast strain capacity to develop on liquid and solid culture media based on the OMWW at different dilutions of 25%, 50%, 75%, raw matter, allowed us to optimize the abatement of the pollutant load, particularly, PC. The results show a significant reduction of 98% for the COD and 97% for the PC, after 1 month of treatment at a dilution of 25%. The PC extracts were characterized by high-performance liquid chromatography, the main identified PC are hydroxytyrosol, tyrosol, caffeic acid, p-coumaric acid and oleuropein. Most of which had disappeared after the treatment. The selected yeast strain was identified by 26S rDNA sequencing and shows that belongs to the species of Rhodotorula mucilaginosa.