Can the red seaweed growing off the coast of Tamil Nadu, Andhra Pradesh and Gujarat be a biodegradable alternative to plastic? While synthetic polymers cannot be completely replaced in the foreseeable future, research at the Marine Biotechnology Division, National Institute of Ocean Technology (NIOT), Chennai, holds out hope that biopolymers from red seaweed (Kappaphycus alvarezii) incorporated with nanoparticles could substitute plastic in certain applications.

These include bioplastic films for packaging, biomedical scaffolds/grafts, 3D printing ink, controlled drug delivery, biosensor, and microbial fuel cell for electric vehicles.

Biopolymers are derived from any plant-based biomass that is renewable, biodegradable, and eco-friendly. Polysaccharide extracts from seaweed — carrageenan biopolymers — are already in use by the food industry. But such extraction uses solvents and chemicals, which also generates waste.

Explains Dr MP Sudhakar, Project Scientist at NIOT: “One advantage in our study is that the use of the whole biomass does not generate waste during material fabrication, but commercial carrageenan needs to be extracted using different solvents and chemicals.”

In the NIOT study, the whole seaweed Kappaphycus alvarezii (containing carrageenan) was used in preparing the bio-nanocomposite film by blending with metal oxide nanoparticles such as zinc oxide, cupric oxide and silicon dioxide. Then its properties were compared with standard refined commercial-grade carrageenan.

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The results were promising, as detailed in a paper published in the International Journal of Biological Macromolecules. The nanoparticles improved the properties of films made from commercial carrageenan as well as whole seaweed. The Kappaphycus-based bio-nanocomposite films performed on par with commercial carrageenan-based bio-nanocomposite films on parameters such as wettability, water vapour properties, thermal stability, anti-bacterial activity, and degradation. Overall, the study concluded that whole seaweed can be used directly for multiple industrial applications without need for solvents and chemicals at the extraction stage.

Notes Sudhakar: “The carrageenan obtained from red seaweed was found suitable for different applications such as packaging, biomedical applications... We incorporated nanoparticles and plasticiser to enhance physical and mechanical properties for specific applications. The bioplastic film degrades within two weeks.”

But how did the researchers zero in on red seaweed? According to Sudhakar, it is easy to extract biopolymer from seaweeds and in higher quantities, too. Also, seaweeds are renewable biomass, cultivable using seawater on shore and offshore. The samples for the study were obtained from the Gulf of Mannar coast in Tamil Nadu.

Following the publication of the study, a few start-ups have approached NIOT for technical help. The three other scientists who contributed to the research were Dr S Venkatnarayanan, Dr NV Vinithkumar, and Dr G Dharani.

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