Isolation and Characterization of Gasoline-Degrading Yeasts from Refined Oil-Contaminated Residues

Abstract

Hydrocarbon-degrading yeasts were isolated from three sites contaminated with products of refined petroleum originating from an oily residue treatment Brazilian company. A selective enrichment technique was used by supplementing medium with gasoline, which resulted in eleven isolates; two identified as Rhodotorula mucilaginosa, one as Rhodosporidium diobovatum, four as Meyerozyma (Pichia) guilliermondii, two as Wickerhamia sp., and two as Meyerozyma sp. The strains were evaluated for their growth capacity in medium containing 1% (v/v) gasoline, kerosene or lubricating oil as the only carbon source; the largest values for cellular biomass and growth rates (μ) were observed with gasoline supplementation. The strains were tolerant to aromatic (toluene and xylene) and aliphatic (hexene and n-heptane) compounds, which are part of the composition of gasoline, at concentrations up to 30 mM toluene (0.3% v/v), 20 mM xylene (0.25% v/v), 80 mM n-heptane (1.17% v/v) and 100 mM hexane (1.33% v/v). The R. mucilaginosa S47 and Meyerozyma sp. SP1 strains showed the greatest degradation percentages of gasoline, and have the potential to be used in the bioremediation of gasoline-contaminated environments.