Selenium reducing Citrobacter fruendii strain KP6 from Mandovi estuary and its potential application in selenium nanoparticle synthesis

Abstract

The present study foregrounds the isolation of selenium tolerant bacteria from Mandovi estuary of Goa, India, known to be contaminated with mining and industrial waste. The isolate was tentatively identified as Citrobacter fruendii strain KP6, which can tolerate up to 60 mM of Na2SeO3 in mineral salt medium (MSM). Bacterial strain KP6 when grown in 60 mM Na2SeO3 in MSM precipitated soluble toxic selenite (Se sup(4+)) into colloidal elemental selenium (Se sup(o), red colored) using glucose as a sole source of carbon. Interestingly, scanning electron micrograph (SEM), transmission electron micrograph (TEM) and X-Ray diffraction (XRD) analysis also confirmed this bioconversion reaction in the formation of nano -sized material extracellularly with the size ranging from 45 to 70 nm. This bioconversion ability of strain KP6 can be exploited for eco-friendly bioremediation of selenite contaminated estuarine sites as well as for synthesis of Se sup(o) nanoparticles having its significance in nanobiotechnology.