Yeast performance in wastewater treatment: case study of Rhodotorula mucilaginosa.

The ability of Rhodotorula mucilaginosa to degrade some phenolic compounds and to grow on olive mill wastewater (OMW) is investigated. R. mucilaginosa isolated from OMW was molecularly identified using 18S RNA sequencing. The biodegradation of six phenolic compounds was studied at an initial concentration of 1 g l(-1). The isolated yeast exhibited a complete degradation of protocatechuic, vanillic and p-coumaric acids and tyrosol. In addition, it reduced 56% and 44% of gallic acid and catechol, respectively. Protocatechuic acid, vanillic acid and p-coumaric acid kinetic degradation showed a simple order equation and the growth rate varied from 0.05 h(-1) to 0.08 h(-1), while tyrosol and catechol degradation fitted a second-degree equation. With OMW as culture medium, R. mucilaginosa was able to reduce 38.38%, 47.69% and 56.91% of chemical oxygen demand (COD) and 5.84%, 27.89% and 34.81% of phenols, respectively, at initial COD concentrations 26,700, 14,400 and 6500 mg l(-1). The use of such red pigmented yeast would present a double interest: first it would purify OMW and, second, an antioxidant would be produced at the same time, having antioxidant properties.