Boosting Breakdown of Harmful Chemicals Using White Rot Fungus and Citric Acid

Jim Crocker
6th July, 2024

Boosting Breakdown of Harmful Chemicals Using White Rot Fungus and Citric Acid

Trametes versicolor

Photo adapted from: Todd Boland / CC BY (Source)

Key Findings

  • Researchers at Beijing University found that citric acid helps the fungus Trametes versicolor degrade the pollutant benzo[a]pyrene in soil
  • Citric acid improved the fungus's environment and boosted its enzyme activity, leading to a 43.7% removal rate of benzo[a]pyrene in 35 days
  • The study shows that using biostimulants like citric acid can enhance the effectiveness of fungi in cleaning up contaminated soils
Polycyclic aromatic hydrocarbons (PAHs) are a group of persistent organic pollutants known for their carcinogenic, mutagenic, and teratogenic effects. These compounds pose significant environmental and health risks due to their stability and persistence in the environment. Traditional methods for remediating PAH-contaminated soils often fall short, necessitating innovative biological approaches. A recent study conducted by researchers at Beijing University of Civil Engineering and Architecture explored the potential of using immobilized Trametes versicolor, a type of white-rot fungus, combined with low molecular weight organic acids to degrade benzo[a]pyrene, a high molecular weight PAH, in soil[1]. The study aimed to address a common challenge in bioremediation: exogenous fungi like Trametes versicolor often face antagonism from indigenous soil microorganisms, which can hinder their effectiveness. The research team hypothesized that low molecular weight organic acids, which are small organic compounds secreted by plants, could improve the nutritional environment for the fungi and enhance their degradation capabilities. The experimental setup involved adding different low molecular weight organic acids to soil samples contaminated with benzo[a]pyrene and then inoculating these samples with immobilized Trametes versicolor. Among the various organic acids tested, citric acid emerged as the most effective, achieving a removal rate of 43.7% after 35 days. This finding is significant as it demonstrates that citric acid can act as a biostimulant, enhancing the fungus's ability to degrade benzo[a]pyrene. To understand the underlying mechanisms, the researchers further investigated the effects of citric acid on Trametes versicolor in a liquid medium. They found that citric acid not only served as a carbon source for the fungus but also promoted the secretion of extracellular proteins and increased laccase activity. Laccase is an enzyme that plays a crucial role in the breakdown of complex organic molecules, including PAHs. By boosting laccase activity, citric acid accelerates the mineralization of benzo[a]pyrene, making it easier for Trametes versicolor to degrade this persistent pollutant. These findings align with earlier studies that have explored the biodegradation of PAHs using various microorganisms and biostimulants. For instance, a study on Anthracophyllum discolor, another white-rot fungus, demonstrated its ability to degrade PAHs in contaminated soil, although the presence of indigenous microorganisms often hindered its effectiveness[2]. Similarly, research on the combined use of plants and bacteria for bioremediation showed that bioaugmentation with Pseudomonas aeruginosa significantly enhanced the removal of petroleum hydrocarbons and heavy metals from co-contaminated soil[3]. These studies collectively highlight the potential of using biostimulants and synergistic microbial interactions to improve bioremediation outcomes. Moreover, the concept of using biostimulants to enhance microbial degradation is supported by research on the biodegradation of benzene and benzo[a]pyrene co-contaminants. This study found that biostimulants like methanol, ethanol, and vegetable oil significantly improved the biodegradation of both contaminants by increasing the activity of specific enzymes and enriching functional microbial genera such as Pseudomonas and Rhodococcus[4]. These genera are known for their robust biodegradation capabilities and were positively correlated with increased enzymatic activity, leading to higher degradation rates. In conclusion, the study by Beijing University of Civil Engineering and Architecture provides compelling evidence that citric acid can be used as an effective biostimulant to enhance the degradation of benzo[a]pyrene by Trametes versicolor in contaminated soils. This approach not only improves the nutritional environment for the fungus but also boosts its enzymatic activity, leading to more efficient PAH mineralization. When considered alongside previous research, these findings underscore the importance of integrating biostimulants and microbial interactions in developing effective bioremediation strategies for persistent organic pollutants.

EnvironmentBiochemMycology

References

Main Study

1) Enhanced biodegradation of benzo[a]pyrene with Trametes versicolor stimulated by citric acid.

Published 4th July, 2024

https://doi.org/10.1007/s10653-024-02053-9

Related Studies

2) Degradation of polycyclic aromatic hydrocarbons by the Chilean white-rot fungus Anthracophyllum discolor.

https://doi.org/10.1016/j.jhazmat.2010.09.020

3) Comparative bioremediation of heavy metals and petroleum hydrocarbons co-contaminated soil by natural attenuation, phytoremediation, bioaugmentation and bioaugmentation-assisted phytoremediation.

https://doi.org/10.1016/j.scitotenv.2015.10.061

4) Mechanisms of biostimulant-enhanced biodegradation of PAHs and BTEX mixed contaminants in soil by native microbial consortium.

https://doi.org/10.1016/j.envpol.2022.120831


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