Cr(VI) reduction by cell-free extracts of Pichia jadinii and Pichia anomala isolated from textile-dye factory effluents

Abstract

Chromium-resistant yeasts isolated from contaminated environments can be used to reduce toxic Cr(VI). This study assessed in vitro reduction of hexavalent chromium using crude chromate reductase (CChR) of Pichia jadinii M9 and Pichia anomala M10, two yeasts isolated from a textile-dye factory effluent. CChRs were characterized based on optimal temperature, pH, use of electron donors, metal ions and initial Cr(VI) concentration in the reaction mixture. Both CChRs showed an increase in Cr(VI) reductase activity with addition of NAD(P)H as electron donor and were highly inhibited by Hg 2+ and Mn 2+. The CChR from P. jadinii M9 showed the highest chromate reductase activity at 60 °C and pH 6.0 in the presence of Cu 2+ or Na +, while P. anomala M10 CChR had the maximum activity at 50 °C and pH 7.0 in presence of Cu 2+. Initial Cr(VI) concentrations of 1.3 and 1.7 mM for CChRs of P. jadinii M9 and P. anomala M10 respectively were inhibitory.