Degradation and decolourization potential of an ligninolytic enzyme producing Aeromonas hydrophila for crystal violet dye and its phytotoxicity evaluation

Abstract

This study deals the biodegradation of crystal violet dye by a ligninolytic enzyme producing bacterium isolated from textile wastewater that was characterized and identified as Aeromonas hydrophila based on the 16 S rRNA gene sequence analysis. The degradation of crystal violet dye was studied under different environmental and nutritional conditions, and results showed that the isolated bacterium was effective to decolourize 99% crystal violet dye at pH 7 and temperature 35 °C in presence of sucrose and yeast extract as C and N source, respectively. This bacterium also produced lignin peroxidase and laccase enzyme, which were characterized by the SDS-PAGE analysis and found to have the molecular weight of ~ 40 and ~ 60 kDa, respectively. Further, the GC-MS analysis showed that CV dye was biotransformed into phenol, 2, 6-bis (1,1-dimethylethyl), 2',6'-dihydroxyacetophenone and benzene by the isolated bacterium and the toxicity of CV dye was reduced upto a significant level as it showed 60%, 56.67% and 46.67% inhibition in seed germination. But, after the bacterial degradation/decolourization, it showed only 43.33%, 36.67% and 16.67% inhibition in seed germination after 24, 48 and 72 h, respectively. Thus, this study concluded that the isolated bacterium has high potential for the degradation/decolourization of CV dye as well to reduce its toxicity upto a significant level.

Keywords: Aeromonas hydrophila; Biodegradation; Crystal violet; GC-MS analysis; Ligninolytic enzyme; Phytotoxicity.