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