Lindane and other HCH Biodegradation: Recent Advances and Research Highlights

Persistent pesticide pollution, particularly from lindane (a type of hexachlorocyclohexane, or HCH), remains a significant environmental threat despite bans.  Residues persist in soil and water, demanding effective remediation.  A recent study by Dr. Di Gregorio’s research group (Bernabei et al., 2024), part of the EU-funded MIBIREM project, focuses on enhancing microbiomes capable of degrading the four main HCH isomers: α, δ, β, and γ-HCH.

Pesticide pollution, especially from organochlorine (OC) pesticides like DDT and lindane, poses severe risks due to their high toxicity and persistence in the environment. Despite bans (since 2008 in the EU), lindane residues are still found in soil and water, necessitating effective remediation strategies.

Bioremediation mechanisms (C)Shutterstock

Lindane and other HCH Biodegradation

In 2024, significant strides have been made in the field of lindane biodegradation. Scientists are leveraging metagenomics to uncover new genes and microbial strains capable of breaking down lindane. By employing synthetic biology techniques, they are enhancing the capabilities of these microbes, making them more efficient in degrading this persistent pollutant. Nanobiotechnology is also playing a crucial role. Researchers are using nanoparticles to improve the bioavailability of lindane, which makes it easier for microbes to access and break it down. This innovative approach is proving to be a game-changer in the field. Studies have shown that mixed microbial consortia, which are groups of different microbial species working together, are more effective at degrading lindane than single strains. This collaborative approach among microbes is yielding promising results. Advances in enzyme engineering have led to the development of more efficient enzymes that can accelerate the breakdown of lindane. These engineered enzymes are designed to be more effective and faster in their action, providing a significant boost to bioremediation efforts.

Finally, progress is being made in applying these laboratory findings to real-world settings. Bioreactors are being optimized for both in-situ (on-site) and ex-situ (off-site) bioremediation, making it possible to clean up lindane-contaminated environments more effectively and sustainably. These advancements are paving the way for more efficient and practical solutions to tackle lindane pollution.

Recent advancements in the field published in 2024 are highlighted below.

Research Highlights

The research group led by Dr. Di Gregorio at the University of Pisa (Italy), a partner in the EU-funded project MIBIREM, published an important study focused on enhancing microbiomes capable of degrading the four main isomers of hexachlorocyclohexane (HCH): α, δ, β, and γ-HCH (Bernabei et al., 2024). This study aimed to select and enhance microbiomes capable of degrading the four main isomers of hexachlorocyclohexane (HCH): α, δ, β, and γ-HCH. Researchers isolated and enriched microbiomes from an HCH-contaminated dumpsite in Italy. They tested these microbiomes both with HCH as the sole carbon source and under co-metabolic growth conditions with glucose. Four microbiomes were assessed for their ability to degrade HCH isomers. The use of a co-metabolic substrate (glucose) during the enrichment process was essential for selecting microbiomes with higher biodiversity. All microbiomes efficiently degraded the α, δ, and γ-HCH isomers. The highest efficiency in degrading the β-HCH isomer was associated with the highest biodiversity of the microbiome. The involvement of specific bacteria, such as Chryseobacterium and Asinibacterium species, was proposed for the increased bacterial load during the HCH degradation process. The study highlights the importance of co-metabolic growth and microbial diversity in enhancing the degradation of HCH isomers. The findings suggest that selecting microbiomes with higher biodiversity can improve the efficiency of bioremediation processes for HCH-contaminated environments. An accopanying video from RemTech 2024:

In another groundbreaking study by Roy et al. (2024), researchers delved into the potential of the yeast strain Meyerozyma caribbica to degrade lindane. This exploration did not stop at M. caribbica alone; the team also investigated its combined efficacy with two bacterial strains, Bacillus velezensis and Priestia megaterium. These microbial strains were sourced from sites contaminated with hexachlorocyclohexane (HCH), a related pollutant. The study found that M. caribbica alone reduced lindane by 86.5%, B. velezensis by 78.6%, and P. megaterium by 77.5%, with a combined M. caribbica and P. megaterium achieving a 90% reduction, and M. caribbica and B. velezensis achieving an 80.9% reduction. This research highlights the promising potential of using these microbial strains, either alone or in combination, for the bioremediation of lindane-contaminated environments.

In a comprehensive study by Boudh et al. (2024), researchers examined soil properties and contamination across six sites in Lucknow and Renukoot, Northern India. They discovered significant differences in soil characteristics, pesticide residues, and the ability of certain microbes to break down lindane.

The study found that Lucknow soils had higher levels of harmful chemicals compared to Renukoot, with specific microbes effectively degrading lindane, and despite higher contamination, Renukoot soils had more microbial biomass, highlighting the need for ongoing monitoring and the use of certain microbes to improve soil health.

Vijayan et al. (2024) explored the use of cyanobacteria, adaptable photosynthetic bacteria, to degrade lindane and other harmful chemicals. Strains like Anabaena and Nostoc have shown promise in breaking down lindane into less harmful substances, offering a potential bioremediation tool. These cyanobacteria not only degrade lindane but also other pesticides, improving soil health and enhancing crop productivity.

In a study by Deng et al. (2024), scientists created transgenic Arabidopsis thaliana plants expressing a bacterial enzyme that breaks down γ-HCH, a harmful pesticide component. These modified plants degraded over 99% of γ-HCH in just 36 hours, demonstrating their potential as a powerful tool for environmental cleanup.

Conclusion

Future research aims to enhance the biodegradation potential of cyanobacteria through genetic engineering and develop cost-effective photobioreactors for large-scale applications. Despite challenges like high costs and contamination risks, ongoing advancements are paving the way for sustainable solutions.

In conclusion, cyanobacteria offer an eco-friendly approach to mitigate pesticide pollution, improve soil health, and support sustainable agriculture. Continuous monitoring and research are essential to fully realize their potential.

 

Author: Tiziana Centofanti

Evvironmental Consultant, RTDS Group

 

References:

Bernabei, G., De Simone, G., Becarelli, S., Di Mambro, R., Gentini, A. and Di Gregorio, S., 2024. Co-metabolic growth and microbial diversity: Keys for the depletion of the α, δ, β and γ-HCH isomers. Journal of Hazardous Materials, 480, p.135963.

Boudh, S., Tiwari, S., Singh, C. and Singh, J.S., 2024. Lindane degradation potential of methanotrophs and soil microbial biomass from HCH contaminated sites. Environmental Advances, 17, p.100581.

Deng, W., Takada, Y., Nanasato, Y., Kishida, K., Stari, L., Ohtsubo, Y., Tabei, Y., Watanabe, M. and Nagata, Y., 2024. Transgenic Arabidopsis thaliana plants expressing bacterial γ-hexachlorocyclohexane dehydrochlorinase LinA. BMC biotechnology, 24(1), p.42.

Roy, A., Dubey, P., Srivastava, A., Kaur, I., Shrivastava, A., Vajpayee, P., Srivastava, S., & Srivastava, P.K. (2024). Exploring the potential of Meyerozyma caribbica and its combined application with bacteria for lindane bioremediation. Chemosphere, 361, p.142413.

Vijayan, P.N., Das, M.M., Haridas, M. and Sabu, A., 2024. Cyanobacterial Degradation of Pesticides. In Waste-to-Wealth (pp. 50-60). CRC Press.

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