Biodegradation and detoxification of malachite green by a newly isolated bioluminescent bacterium Photobacterium leiognathi strain MS under RSM optimized culture conditions

Abstract The isolated bioluminescent bacterium was identified as Photobacterium leiognathi strain MS using 16 S rRNA sequence analysis and subjected to malachite green (MG) dye degradation. The Box-Behnken based response surface methodology (RSM) was employed in optimizing medium conditions exhibiting maximum growth at pH 8.0, temperature 30 °C, NaCl 3.5%, and peptone 6.5%. Photobacterium leiognathi strain MS was capable of tolerating high concentration of MG (1.0 gL-1) with 92.50% decolorization potency within 24 h. UV-Vis, FTIR, and LC-MS QTOF analyses confirmed biodegradation of MG into several metabolites as well as its catabolism pathway. A significant increase in the activity of laccase was obtained which revealed its major involvement in the degradation of MG dye. Moreover, phytotoxicity and cytotoxicity analyses illustrated that the metabolites generated were less toxic than the parental compound.