Scientists at the Indian Institute of Technology Guwahati now report a biological answer to treating the Azo dye effluents after the fabric is dyed. Their tool is an organism far smaller than the plant normally used to treat wastewater: a bacterium.
The team has characterised a previously undescribed bacterium, Brevundimonas sp. AJZ05, isolated at a native textile effluent discharge site. In laboratory trials it broke down 98.50% of Direct Blue-6 (DB-6), a widely used synthetic azo dye.
Azo dyes are defined by the azo bond (–N=N–), which gives them intense colour and durability but also makes them stubborn under conventional effluent treatment methods.
Analysis showed that AJZ05 generates azoreductase, an enzyme that targets the azo bond and helps split the dye molecule apart.
Applying Response Surface Methodology, a statistical optimisation approach, the researchers pinpointed operating conditions that lifted dye degradation and enzyme output together. Under those settings, the strain achieved 98.50% degradation of DB-6, alongside azoreductase activity of 0.761 U/mL.
Decolourising effluent is not the same as detoxifying it. Certain treatment routes leave water looking cleaner while potentially harmful compounds persist within it. The IIT Guwahati group therefore examined the metabolites produced during bacterial degradation and evaluated their toxicity.
Dr Selvaraju Narayanasamy, associate professor in the Biochemical and Environmental Engineering Laboratory, Department of Biosciences and Bioengineering, IIT Guwahati, said the study deliberately looked beyond colour removal.
His team characterised the metabolites generated during biodegradation and tested how toxic they were.
After bacterial treatment, the breakdown products proved non-toxic. This suggests the process may convert the dye into safer substances rather than merely giving polluted water a cleaner appearance.
The researchers describe the outcome as a promising biological pathway towards safer, more sustainable effluent treatment.
The strain also tolerated several metal ions, a useful trait given that genuine industrial wastewater tends to contain a blend of contaminants rather than a lone pollutant.
The work remains at laboratory stage, though the team is already weighing how the approach could be adapted for commercial deployment.
Narayanasamy said the group is working to turn bench-scale findings into a practical, scalable treatment technology. The next step is to immobilise AJZ05 on a suitable support matrix, with the aim of improving its stability, operating performance and reusability.
The researchers intend to build a continuous-flow system for removing azo dyes from textile effluent, with the longer-term goal of moving the microbial platform towards industrial use.
Funding came through the Prime Minister’s Research Fellowship, with additional support from IIT (BHU), Varanasi. The findings were published in ‘Environmental Geochemistry and Health’.
Should development continue, the microbe could form part of a far bigger solution: treating industrial effluent while cutting reliance on energy-hungry, chemical-intensive processes. It shows that a cleaner fix for a major environmental problem can sometimes begin with something as tiny as a microbe.
