Strain Improvement of Selected Bacteria using Physical Mutagen for Bioremediation of Hexavalent Chromium: A Comparative Study
Bioremediation using microbes is eco-friendly and economical. There is an increased demand for improvised
strain of microbes for chromium removal from effluents. Strain improvement using mutagens are promising for generation
of strains with better chromium removal efficiency. The present work aims at improvising the bacterial strainsBacillus
subtilis, Bacillus amyloliquifaciensand Micrococcus luteus (isolated from an indigenous source of electroplating effluent of
an industry in Peenya, Bangalore)by inducing random physical mutations with ultraviolet light and studying its impact on
chromium remediation capacity. The study also reveals the effect of chromium on growth of microbes. UV survival curve
was plotted and mutants with more than 50 % survival rate, were chosen for remediation studies. Wild type and mutants
were assessed for chromium removal efficiency using diphenylcarbazide method. Bacillus amyloliquifaciens exposed to UV
radiation for 80 minutesshowed 100 % chromium removal efficiency in 8 hours, while the wild type remediated in 10 hours.
Bacillus subtilis that was exposed for 120 min showed 100 % removal efficiency in 17 hours, while the wild type remediated
96 % of chromium in 19 hours. Both wild type and mutants of Micrococcus luteusremoved 96 % chromium in 18 hours.
This study indicates the successful strain improvement of Bacillus subtilis and Bacillus amyloliquifaciens in generating
mutant with a better ability for chromium removal, while Micrococcus luteus being resistant to UV irradiation failed to show
any improvement in removal efficiency of chromium.
Keywords - Chromium, Microbial remediation, Strain improvement, Bacillus amyloliquifaciens, Bacillussubtilis,
Micrococcus luteus, Ultraviolet light.