Bioreduction of chromium (VI) to chromium (III) by a novel yeast strain Rhodotorula mucilaginosa (MTCC 9315)

Abstract

Introduction of heavy metal compounds like chromium, lead, arsenic and mercury into the environment generally induces morphological and physiological changes in the microbial communities hence exerting a selective pressure on the microorganisms. Generally, sites which are contaminated with heavy metals are the sources of metal resistant microorganisms. This paper describes the bioreduction of Cr⁶⁺ to Cr³⁺ by a novel strain Rhodotorula mucilaginosa (MTCC 9315). The yeast is very efficient in Cr⁶⁺ reduction. It is shown that the reduction of Cr⁶⁺ to Cr³⁺ species occurs extracellularly by analyzing the supernatant of the yeast extract peptone sucrose medium (YEPS) thus supporting the assumption about the existence of an extra-cellular pathway of Cr⁶⁺ reduction. Furthermore, it is demonstrated that R. mucilaginosa cells are salt tolerant. It is thus suggested that isolated yeast biomass can be used as sources of Cr⁶⁺ reducer, and the resin formulated in the present study may be used as biofilter to filter out Cr⁶⁺ ions. The yeast can also be a good supplier of Cr-chelators with potential pharmacological applications.

Keywords: Chromium bioreduction, resin, industrial effluent, metal resistant microorganisms, yeast, biofilter