Isolation and Identification of Novel Chromium Tolerant Bacterial Strains From a Heavy Metal Polluted Urban Creek: An Assessment of Bioremediation Efficiency and Flocculant Production

Uncontrolled discharge of industrial effluents and wastewaters has resulted in a significant increase in Hexavalent Chromium Cr(VI) levels in urban rivers and tidal inlets such as Mumbai's Versova Creek. Mechanical removal of such heavy metals is both expensive and time-consuming. Indigenous bacteria' ability to bioremediate Cr(VI) could be a viable option. In this study, six indigenous bacteria were isolated from the sediments of Versova Creek and that were capable of tolerating Cr(VI) up to 2000 ppm. They belonged to the genera Bacillus and Pseudomonas as confirmed from the 16S rRNA sequencing. The in-vitro metal removing capacity of the pure cultures ranged from 90%-96% when the culture medium (pH 7.0) was supplemented with 400 ppm of Cr(VI) and incubated at 37 oC. The isolates were also tested for bioflocculant synthesis for bioflocculant assisted Cr(VI) biosorption, two of the isolates (AKVCRR04 and AKVCRR05) showed high flocculation activity 89.75 and 89.88% respectively by the 5th day of incubation. The growth profile of isolates and final pH with respect to the flocculation activity assay revealed bioflocculant production to peak either during or in the late stationary phase. These bacteria highly tolerant to Cr(VI) have significant potential for Cr(VI) biosorption and removal/ detoxification from contaminated sites such as Versova creek.