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Cr(VI) reduction from contaminated soils by Aspergillus sp. N2 and Penicillium sp. N3 isolated from chromium deposits
Tsubasa Fukuda1, Yasuhiro Ishino, Akane Ogawa
1Graduate School of Environmental Engineering, The University of Kitakyushu, 1-1 Hibikino, Wakamatsu-ku, Kitakyushu, Japan.
Abstract:
Aspergillus sp. N2 and Penicillium sp. N3 are chromate-resistant filamentous fungi that were isolated from Cr(VI) contaminated soil based on their ability to decrease hexavalent chromium levels in the growth medium. After 120 h of growth in a medium containing 50 ppm Cr(VI) at near neutral pH, Aspergillus sp. N2 reduced the Cr(VI) concentration by about 75%. Penicillium sp. N3 was able to reduce the Cr(VI) concentration by only 35%. However, Penicillium sp. N3 reduced the Cr(VI) concentration in the medium by 93% under acidic conditions. Interestingly, the presence of Cu(II) enhanced the Cr(VI) reducing ability of Aspergillus sp. N2 and Penicillium sp. N3 at near neutral pH. Aspergillus sp. N2 and Penicillium sp. N3 reduced the Cr(VI) concentration in the growth medium to a virtually undetectable level within 120 h. For both Aspergillus sp. N2 and Penicillium sp. N3, mycelial seed cultures were more efficient at Cr(VI) reduction than conidium seed cultures. The mechanisms of Cr(VI) reduction in Aspergillus sp. N2 and Penicillium sp. N3 were enzymatic reduction and sorption to mycelia. Enzymatic activity contributed significantly to Cr(VI) reduction. Aspergillus sp. N2 and Penicillium sp. N3 reduced the levels of Cr(VI) in polluted soil samples, suggesting that these strains might be useful for cleaning up chromium-contaminated sites.
Insights
Chromate-resistant fungi, Aspergillus sp. N2 and Penicillium sp. N3, effectively reduce hexavalent chromium (Cr(VI)) in contaminated soil. Mycelial cultures and the presence of Cu(II) enhance this bioremediation potential.
Area of Science:
- Environmental Microbiology
- Bioremediation
- Fungal Biotechnology
Background:
- Hexavalent chromium (Cr(VI)) is a highly toxic environmental pollutant.
- Chromate-resistant filamentous fungi offer potential solutions for Cr(VI) remediation.
- Isolation and characterization of novel fungal strains for heavy metal detoxification are crucial.
Purpose of the Study:
- To isolate and characterize chromate-resistant fungi for Cr(VI) reduction.
- To evaluate the efficiency of Aspergillus sp. N2 and Penicillium sp. N3 in reducing Cr(VI) under various conditions.
- To investigate the mechanisms and factors influencing fungal Cr(VI) reduction.
Main Methods:
- Isolation of Cr(VI)-resistant fungi from contaminated soil.
- Cultivation of Aspergillus sp. N2 and Penicillium sp. N3 in Cr(VI)-containing media.
- Assessment of Cr(VI) reduction percentages under neutral and acidic pH, with and without Cu(II).
- Comparison of Cr(VI) reduction by mycelial versus conidium seed cultures.
- Analysis of Cr(VI) reduction mechanisms (enzymatic and sorption).
Main Results:
- Aspergillus sp. N2 achieved ~75% Cr(VI) reduction at neutral pH, while Penicillium sp. N3 achieved 35% (neutral) and 93% (acidic).
- Cu(II) enhanced Cr(VI) reduction by both fungi at neutral pH, leading to undetectable levels within 120 h.
- Mycelial seed cultures were more effective than conidium seed cultures for Cr(VI) reduction.
- Enzymatic reduction and sorption to mycelia were identified as key Cr(VI) reduction mechanisms.
Conclusions:
- Aspergillus sp. N2 and Penicillium sp. N3 demonstrate significant Cr(VI) reduction capabilities.
- Optimized conditions (pH, Cu(II), mycelial culture) enhance fungal bioremediation efficiency.
- These fungal strains show promise for the cleanup of Cr(VI)-polluted soils.
