Hexavalent chromium reduction by immobilized cells of Bacillus sphaericus AND 303

Abstract

Bacillus sphaericus AND 303, a Cr(VI)-resistant and reducing bacterium reported from serpentine outcrops of

Chromium in Environment, Its Toxic Effect from Chromite-Mining and Ferrochrome Industries, and Its Possible Bioremediation

“…c. Immobilized cell technique in this technique, bacterial cells or enzymes are fixed to some polymer matrix such as polyacrylamide, polyester, polyurethane, diatomite, agar-agar, agarose and gelatine via chemical or physical methods (Pal et al 2013;Elangovan et al 2009). Immobilized cell techniques have many advantages like (1) being cost effective as cells/enzymes are reusable, (2) providing high product yields as it allows for high cell density in small space, (3) protection from shear forces, and (4) providing improved operational stability (Elangovan et al 2009;Zhu 2007).…”

“…Immobilized cell techniques have many advantages like (1) being cost effective as cells/enzymes are reusable, (2) providing high product yields as it allows for high cell density in small space, (3) protection from shear forces, and (4) providing improved operational stability (Elangovan et al 2009;Zhu 2007). Several studies have been reported to use immobilized cell and the cell-free enzyme extract of various bacteria for bioremediation of chromium from contaminated water and wastewater (Camargo et al 2003;Pal et al 2013;Elangovan et al 2009;Tekerlekopoulou et al 2013).…”

Improvement of simultaneous Cr(VI) and phenol removal by an immobilised bacterial consortium and characterisation of biodegradation products

“…It was observed that Cr(VI) removal by the immobilised consortium increased when increasing the initial metal concentration, but was incomplete with any assayed condition (Figure 2). Similarly, other immobilised bacterial strains achieved better results in Cr(VI) removal upon being exposed to higher concentrations of the metal [16,25]. This performance has been related to the diffusion of contaminants inside the matrix, which depends mostly on the concentration of the substance to be internalised.…”

“…A common characteristic of immobilised systems is that their remediation efficiency diminishes over time, mostly when they are used for the removal of metals [16,25,35,36]. This behaviour has been associated with increased mechanical instability and gradual cell leakage from the beads during reutilisation cycles [37].…”

“…Alginate is one of the most frequently used matrices for this purpose. It is a highly porous, biodegradable polymer that provides rapid and simple aqueous immobilisation [14] and for this reason alginate entrapped cells have been extensively used for bioremediation of organic and inorganic contaminants [14,15,16].…”