Lignin from Agricultural Waste Helps Make Useful Nanocomposites

Agro waste can have several useful applications. Scientists at the Centre of Innovative and Applied Bio-processing (CIAB), Punjab have developed a lignin-based nanocomposite that could potentially have commercial value. Microbial test results show that, in the long run, the lignin-based nanomaterial can be used as an additive in coating & packaging materials.

It is important to mention that Lignin is a complex organic polymer rich in polyphenols with antimicrobial qualities. It can be found in all dry plants that includes crop residues & the woody bark of trees. Plentiful quantities of lignin are generated as post-harvest agro-biomass & in paper and pulp industries every year that often go waste.

On the other hand, burning of post-harvest biomass such as straw is a regular practice among the farmers that leads to severe environmental pollution. Dr Jayeeta Bhaumik, lead researcher of the study said, “We took up the challenge of converting agro-waste into value-added nanomaterials with antimicrobial properties, thereby not only reducing the pollution but trying to add to farmers’ income”.

The team focussed on gold-silver bimetallic nanoparticles to make use of their novel physicochemical properties & utilized kraft lignin as the matrix material. The researchers applied ‘green’ & reproducible techniques, instead of using harsh chemicals & high temperatures to synthesise nanocomposite to obtain nanomaterials. The method involved a single-step method utilising lignin as the sole source for reducing, capping & stabilising the nano-agents.

After establishing structural stability & morphology of the nanocomposite, the material was subjected to several microbial assays to assess its antimicrobial quality. The results showed that the lignin-nanocomposite preserved antimicrobial & antioxidant qualities of lignin.

Dr Bhaumik explained, “The lignin-bimetallic nano complexes were found to show excellent targeting of microbes by the mechanism of reactive oxygen species production & membrane disruption of microbial cells, revealing that nano-complexes were internalized in microbial cells”.

She added that the new material might contribute to complete valorisation of lignin & large scale production costs & scalability have to be worked out.

Other members of the team were - Neeraj Singh Thakur, Sanjam Chandna, Ravneet Kaur and Yeddula Nikhileshwar Reddy. The research results have been published in the ACS Biomaterials Science and Engineering journal.