Bio-statistical evaluation of cultural conditions on industrial textile dye decolourisation using a native bacterium Micrococcus endophyticus (ES37)

An indigenous dye-decolourising bacterium Micrococcus endophyticus (ES37) was isolated from dye contaminated soil and identified by 16S rDNA sequencing. The bacterial strain ES37 exhibited 97.19% of dye removal capacity in Luria-Bertani broth composition within 48 h, while the culture containing yeast extract showed 53.4% decolourisation in 72 h. In the absence of carbon and nitrogen sources, the bacterial strain failed to decolourise the dye, even on extended incubation. The effect of environmental factors on decolourisation was investigated by Plackett–Burman design and the significant parameters were lactose, yeast extract and pH. Optimisation of these factors was done by response surface methodology with central composite design; the decolourisation ranged from 0.43 to 77.49%. The optimised levels of lactose, yeast extract and pH were found to be 0.85% (w/v), 0.71% (w/v) and 7.5%, respectively. Under the optimal conditions, decolourisation of remazol golden yellow by ES37 strain was 81.61%, which was in agreement with the predicted value of 79.99%. These findings revealed the interactions and importance of environmental factors on dye decolourisation using native bacteria and also their standard point for an effective dye removal process.