Purification of Chromate(VI) Reductase from Lichen photobiont, Trebouxia erici and its Effect on Wastewaters.

Abstract

Chromate (VI) reductase (CR) was isolated and purified from soluble extracts obtained from lichen photobiont, Trebouxia erici by salt gradient and sequential chromatographic methods. The soluble extract was fractionated by ammonium sulphate precipitation, dialysed and applied onto CM-Sephadex ion-exchange column. The active fractions were pooled and chromatographed on a SephadexG-75 column .Electrophoresis on SDS-PAGE analysis of the partially purified chromate(VI) reductase revealed two bands with  molecular weights of 39 kDa and 63 kDa . The enzyme had maximum activity at pH 6 and an optimum temperature of 40^oC. The enzyme was stable between pH 4 and 7. Double reciprocal plots of initial velocity data, using NADH as substrate, gave a K_M value of 118 μM and V_max of 0.173 μmol/min/mg respectively . Studies on the effect of chromium reductase on synthetic wastewater shows that chromate(VI) reductase (CR) was effective in the reduction of over 65% of Cr (VI) to Cr (III) in 4h. The bioremediation potential of chromate(VI) by lichen was discussed.

Keywords: Chromate(VI) reductase, purification, bioremediation, wastewater.