Degradation of azo dye methyl red by alkaliphilic, halotolerant Nesterenkonia lacusekhoensis EMLA3: application in alkaline and salt-rich dyeing effluent treatment

摘要

Effluents from textile industries are highly colored due to vast use of various azo dyes and color is the first visual indicator of pollution. Biological treatment of textile effluent is often hampered due to the alkaline pH and high salinity; a common characteristic of many textile industrial wastewaters. Considering this, the present study explores the potential of a newly isolated halotolerant and alkaliphilic bacterium Nesterenkonia lacusekhoensis EMLA3 for degradation of methyl red (MR) dye under alkaline condition. Strain EMLA3 showed 97% degradation of 50 mg L-1 MR after 16 h at initial pH of 11.5 in nutrient medium. Dye degradation by the isolate is supported by the formation of low-molecular weight metabolites as divulge through GC-MS & FTIR studies Optimum dye degradation was observed in the pH range of 8.0-11.5 and temperature range of 30-35 degrees C. Significant MR degrading activity of the strain could be achieved in the presence of very high salt level (100-120 g L-1 NaCl) and in co-presence of different heavy metals. Application of strain to alkaline pH, salt, and heavy metals laden-textile effluent resulted in overall 83% dye removal from the effluent after 120 h of treatment under static condition. Furthermore, the property of microbe to drop-down the pH of wastewater from 11.5 to 8.60 after treatment also lowers the need of additional neutralization treatment. The entire study thus comes out with novel application of N. lacusekhoensis-a less explored extremophilic bacterium-for treatment of alkaline and salt-rich azo dye-containing wastewaters.