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.

Key words: Chromium bioreduction, resin, industrial effluent, metal resistant microorganisms, yeast, biofilter.

Abbreviation

Abbreviations: PDA, Potato dextrose agar; NA, nutrient agar; YEPD, yeast extract peptone dextrose; YEPS, yeast extract peptone sucrose; YEPM, yeast extract peptone maltose; EPS, exopolymeric substances.