IIT Guwahati Develops Bacterial Process To Treat Toxic Textile Dyes

Researchers at the Indian Institute of Technology Guwahati (IIT Guwahati) have developed a biological approach to treat textile wastewater containing toxic azo dyes, using a novel bacterium that degraded 98.50% of a commonly used synthetic dye under optimised laboratory conditions.

The study demonstrated the ability of Brevundimonas sp. AJZ05 to degrade Direct Blue-6 (DB-6), a widely used synthetic dye in textile processing. The researchers also found that the degradation products formed during bacterial treatment were non-toxic, indicating the potential of the process to convert the dye into safer compounds rather than merely removing its visible colour.

Azo dyes are widely used in the textile industry but are difficult to remove because of their stable chemical structure. The azo bond (–N=N–) present in these dyes contributes to their colour and chemical stability, making them resistant to several conventional wastewater treatment processes.

Untreated textile effluents containing such dyes can pose risks to aquatic ecosystems and potentially affect human health. Conventional chemical and physicochemical treatment methods can also be energy-intensive and may result in the generation of secondary pollutants.

For the study, the researchers isolated Brevundimonas sp. AJZ05 from a native textile effluent discharge site. The bacterium was found to produce azoreductase, an enzyme capable of breaking the azo bond responsible for the colour and stability of the dyes.

The research team used a statistical multi-objective optimisation approach based on Response Surface Methodology to simultaneously optimise dye degradation and azoreductase production. Under the optimised conditions, Brevundimonas sp. AJZ05 achieved 98.50% degradation of DB-6, with azoreductase activity reaching 0.761 U/mL.

Dr Selvaraju Narayanasamy, Associate Professor at the Biochemical and Environmental Engineering Laboratory, Department of Biosciences and Bioengineering, IIT Guwahati, said analysing the metabolites generated during biodegradation and assessing their toxicity was an important part of the study.

“The degradation products were found to be non-toxic after bacterial treatment,” Dr Narayanasamy said. According to the researchers, this suggests that the bacterial process could potentially transform the dye into safer compounds rather than simply reducing the visible colour of contaminated water.

The researchers are now working to take the technology beyond laboratory conditions. The next stage involves immobilising Brevundimonas sp. AJZ05 in a suitable support matrix to improve its stability, operational performance and reusability.

The study also found that the bacterium could tolerate several metal ions, a characteristic that may be relevant for industrial wastewater treatment, where effluents can contain multiple contaminants.

The research was supported by the Ministry of Education through the Prime Minister’s Research Fellowship, with support from the Department of Chemical Engineering and Technology, IIT (BHU), Varanasi.

The findings have been published in the peer-reviewed journal Environmental Geochemistry and Health. The paper was co-authored by Ajithkumar Veluchamy, Jothika Jeyabalan and Dr Selvaraju Narayanasamy of IIT Guwahati, along with Dr Ankur Verma of the Department of Chemical Engineering and Technology, IIT (BHU), Varanasi.