Biodegradation of hexachlorocyclohexane (HCH) by microorganisms

Area of Science:

• Environmental Science
• Microbiology
• Environmental Chemistry

Background:

• Lindane, the gamma-isomer of hexachlorocyclohexane (HCH), is a persistent organochlorine pesticide.
• Technical Lindane contains multiple HCH isomers (alpha, beta, delta, gamma) with varying properties, all recognized as toxic global pollutants.
• While HCH biodegradation is studied in labs, limited data exists on full-scale in situ bioremediation of diverse isomers.

Purpose of the Study:

• To review the current knowledge on HCH isomer biodegradation, focusing on Lindane.
• To identify knowledge gaps in the in situ bioremediation of HCH isomers in soil.
• To highlight the need for large-scale studies on HCH bioremediation, particularly in contaminated soils.

Main Methods:

• Literature review of studies on HCH biodegradation in various media (soil, slurry, culture).
• Analysis of research on microbial degradation pathways and genetic characterization of HCH-degrading enzymes.
• Examination of factors influencing HCH degradation in soil, including environmental conditions and amendments.

Main Results:

• Soil microorganisms capable of degrading HCH have been identified, with key degradation genes characterized in some strains.
• HCH biodegradation occurs under both oxic and anoxic conditions, with mineralization primarily in oxic environments.
• Degradation is influenced by moderate temperatures, near-neutral pH, moisture content, soil texture, and organic matter.

Conclusions:

• HCH isomers are biodegradable, but effective in situ bioremediation requires further investigation.
• Optimizing bioremediation protocols for large-scale application, especially in soils with high HCH concentrations, is crucial.
• More research on the effects of soil amendments and nutrients is needed to enhance HCH bioremediation efficiency.