Research from the Nanoscience Center of the University of Jyväskylä, Finland, has revealed that lignin, a polyphenol, important for plant structure, has antimicrobial activity against viruses and bacteria. The results highlight that lignin, which is also an important by-product from wood industry, has potential as promising green alternative to synthetic antimicrobial agents for coating agents, packaging material, or surface disinfectants. The research is fruitful collaboration with Spinnova Oy and CH Bioforce.
The University of Jyväskylä study used a simple water-based extraction method, in which lignin was isolated in high purity from birch chips, wheat straw and oat husks. The method allows the products to maintain a high total phenol content and effectively remove carbohydrate impurities.
- We revealed that these aqueous-based lignin samples demonstrated strong antiviral efficacy against non-enveloped enteroviruses but also good activity against enveloped coronaviruses and tested bacteria, rejoices Professor of Cell and Molecular Biology Varpu Marjomäki from the University of Jyväskylä.
In addition to testing human seasonal coronavirus (HCoV-OC43) in Biosafety level 2 (BSL-2) laboratory, the research team evaluated the efficacy against SARS-CoV-2 in a BSL-3 laboratory in Jyväskylä.
- The results revealed that lignins exhibited much stronger antiviral efficacy against SARS-CoV-2 causing COVID-19, in comparison to the HCoV-OC43 causing common cold. Furthermore, the lignins had inhibitory effects on Staphylococcus aureus and Escherichia coli, explains Doctoral Researcher Jun Liu from the University of Jyväskylä.
Environmentally friendly protection against microbes
By employing a range of classical and in-house-developed biochemical and imaging techniques, the research team was able to investigate the underlying antimicrobial mechanisms.
- The results revealed that lignins inactivate enteroviruses by stabilizing and aggregating viral particles, thereby reducing their entry into the host cells and by preventing the release of the infective RNA genome in the cells, says Marjomäki.
In contrast, transmission electron microscopy and confocal microscopy revealed that lignin solutions disrupted the structural integrity of coronavirus particles, hence reducing their ability to bind to and infect host cells. Electron microscopy also revealed clear effects on bacterial cell membrane and aggregation of bacterial internal materials. Professor of Cell and Molecular Biology Lotta-Riina Sundberg says this suggests that active chemical groups penetrate the cells, ultimately leading to bacterial dysfunction.
- Research shows that lignin can be an environmentally friendly alternative to synthetic microbe-repellent substances. It can be used in coatings, packaging, and disinfectant products in a safer and more sustainable way, specifies Sundberg.
The work was done under tight collaboration between University of Jyväskylä, Spinnova Oy and CH Bioforce.