Screening of decolourizing yeasts with dye assimilation ability from Las Yungas rainforest

Abstract

Environmental pollution by textile-dye containing wastewaters is a matter of worldwide concern. Yeasts bioremediation, a poorly explored and less exploited methodology, stands out as an interesting approach supported on their metabolic diversity and high growth rates. In this work, a screening protocol based on dye tolerance and dye assimilation ability on solid media was performed with a 2000 mg/L dye mixture. Thirty-nine yeast isolates from “Laurel del Monte” underlying soils from “Las Yungas” (Tucumán, Argentina) were obtained. Based on decolourization haloes and colony dyeing, 15 isolates showed the highest decolourization ability on agar plates containing Vilmafix® Blue RR-BB, Vilmafix® Red 7B-HE, Vilmafix® Black B-V and Vilmafix® Yellow 4R-HE, either alone or as a mixture. Screening on agar plates with synthetic media supplemented with each dye as sole C or N source, led to the selection of 10 isolates. Microsatellite RAPD analysis enabled the discrimination of these isolates into six groups. Following tests consisted on the analysis of growth and decolourization kinetic profiles, along with the production of Manganese peroxidase, laccase and tyrosinase activities in dye-supplemented (200 mg/L) liquid media. Time-dependent supernatant spectra, growth curves and enzymatic activities led to the selection of the two most promising isolates for future experiments