Metal resistance and uptake by Trichosporon asahii and Pichia kudriavzevii isolated from industrial effluents

Metal-resistant yeast strains, Trichosporon asahii and Pichia kudriavzevii, were grown-well onto YPD medium at 37°C (pH 6) and 30°C (pH 7), respectively. Tolerance values determined in T. asahii were 35 mM (Pb), 33 mM (Cu), 30 mM (As) and 10 mM (Cd) while P. kudriavzevii resisted up to 31 mM (Pb), 27 mM (Cu), 15 mM (Cd) and 12 mM (As). Yeasts grown in Minimal Salt Medium (MSM) were treated separately with metal challenge (100 mg/L) for 2 days. T. asahii showed elevated glutathione (GSH) level with Cd (83.06), As (81.87), Pb (66.88) and Cu (56.19) mM/g which was 70 (Cu), 69.87 (Pb), 56.47 (As) and 52.76 (Cd) in P. kudriavzevii as compared to the control. The glutathione (GSH): glutathione disulfi de (GSSG) ratio was decreased with all treated heavy-metals except Cd in T. asahii and increased with Cu and Pb in P. kudriavzevii. T. asahii could remove 78% (Cd), 72% (As), 85% (Cu) and 94.5% (Pb) from the medium after 12 days while was able to uptake 44.8, 41, 62 and 72 mg/g Cd, As, Cu and Pb, respectively. Likewise, P. kudriavzevii was able to remove 61% (Cd), 62% (As), 61% (Cu) and 87% (Pb) after 12 days of incubation and also showed capacity to uptake 36.8, 48, 40 and 57 mg/g Cd, As, Cu and Pb, respectively. Total protein profi ling of yeasts revealed marked differences in banding pattern due to increased oxidation under metal stressed conditions. High metal uptake ability makes T. asahii and P. kudriavzevii potential candidates to remove metals from the environment.