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Remediation of Metal Contaminated Soil by Organic Metabolites from Fungi I—Production of Organic Acids
Örebro University, School of Science & Technology, Örebro, Sweden; SAKAB AB, Kumla, Sweden. (MTM)
Örebro University, School of Science and Technology. (MTM)
SAKAB AB, Kumla Sweden.
Örebro University, School of Science and Technology. (MTM)ORCID iD: 0000-0002-2104-4593
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2008 (English)In: Water, Air and Soil Pollution, ISSN 0049-6979, E-ISSN 1573-2932, Vol. 205, no 1-4, 215-226 p.Article in journal (Refereed) Published
Abstract [en]

Investigations were made on living strains offungi in a bioremediation process of three metal (lead)contaminated soils. Three saprotrophic fungi (Aspergillusniger, Penicillium bilaiae, and a Penicillium sp.) wereexposed to poor and rich nutrient conditions (no carbonavailability or 0.11 M D-glucose, respectively) andmetal stress (25 μM lead or contaminated soils) for5 days. Exudation of low molecular weight organicacids was investigated as a response to the metal andnutrient conditions. Main organic acids identified wereoxalic acid (A. niger) and citric acid (P. bilaiae).Exudation rates of oxalate decreased in response tolead exposure, while exudation rates of citrate were lessaffected. Total production under poor nutrient conditionswas low, except for A. niger, for which nosignificant difference was found between the poor andrich control. Maximum exudation rates were 20 μmoloxalic acid g^−1 biomass h^−1 (A. niger) and 20 μmolcitric acid g^−1 biomass h^−1 (P. bilaiae), in the presenceof the contaminated soil, but only 5 μmol organic acidsg^−1 biomass h^−1, in total, for the Penicillium sp. Therewas a significant mobilization of metals from the soilsin the carbon rich treatments and maximum release ofPb was 12% from the soils after 5 days. This was notsufficient to bring down the remaining concentration tothe target level 300 mg kg^−1 from initial levels of 3,800,1,600, and 370 mg kg^−1in the three soils. Target levelsfor Ni, Zn, and Cu, were 120, 500, and 200 mg kg^−1,respectively, and were prior to the bioremediationalready below these concentrations (except for Cu Soil1). However, maximum release of Ni, Zn, and Cu was28%, 35%, and 90%, respectively. The release of metalswas related to the production of chelating acids, but alsoto the pH-decrease. This illustrates the potential to usefungi exudates in bioremediation of contaminated soil.Nonetheless, the extent of the generation of organicacids is depending on several processes and mechanismsthat need to be further investigated.

Place, publisher, year, edition, pages
Berlin, Germany: Springer, 2008. Vol. 205, no 1-4, 215-226 p.
Keyword [en]
Bioremediation, Citric acid, Fungi, Lead, Organic acids, Oxalic acid
National Category
Natural Sciences Environmental Sciences
Research subject
Environmental Chemistry
Identifiers
URN: urn:nbn:se:oru:diva-11843DOI: 10.1007/s11270-009-0067-zISI: 000272851000016Scopus ID: 2-s2.0-75049083063OAI: oai:DiVA.org:oru-11843DiVA: diva2:351661
Available from: 2010-09-15 Created: 2010-09-15 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Impact of root and mycorrhizal exudation on soil carbon fluxes: influence of elevated CO2 and metals
Open this publication in new window or tab >>Impact of root and mycorrhizal exudation on soil carbon fluxes: influence of elevated CO2 and metals
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The thesis concerns the behavior of root and ectomycorrhizal (ECM) exudates. In particular, the dynamics of soluble low molecular weight (LMW) organic compounds such as organic acids (LMWOAs), amino acids, monosaccharides, and dissolved organic carbon (DOC) have been studied. Our knowledge of exudation rates for tree roots and especially associated ECM is limited, and also factors influencing exudation rates. Two environmental factors, metal stress and elevated atmospheric CO2 level, have been investigated. Both are of great environmental concern, but function in different ways (detoxification and C allocation) and may be highly important for the C flux caused by root/ECM exudation. The project has been carried out with mycorrhizal and nonmycorrhizal (NM) Scots pine seedlings, or saprotrophic fungi, under both sterile and non-sterile (soil) conditions. Analytical determination of exudates and calculation of exudation rates have been major tools for assessment. Assessing the possibility of using naturally occurring chelating agents (e.g. citrate and oxalate) for bioremediation of metals contaminated soils and development and validation of analytical techniques have been additional foci. The results show that from soil-living fungi and ectomycorrhizal roots exudation rates of especially LMWOAs increase significantly at Cd and Pb stress (1-100 μM), while As (as arsenate) and mixtures of metals with As have little effect. The impact of ECM fungi is large and much higher exudation rates are found when the symbionts are present both for controls and metal treatments compared to NM plants. In soil systems there was a significant mobilization of metals from soils under presence of saprotrophic fungi. Both N as well as elevated CO2 (700 ppm) causes sizable increases in exudation rates, independent of biomass, and is a finding that suggests that the availability of easily degradable carbon in soil raises, which may be highly important for the carbon flux in soil. Mycorrhizal seedlings (10 months old) increased total soil respiration ~50% compared to controls without plants in non-sterile soil systems. Key words: amino acids, 13C, carbon cycle, ectomycorrhiza, elevated CO2, exudation, DOC, LMWOA, metal stress, monosaccharides, oxalate, Pinus sylvestris, saprotrophic fungi, soil respiration

Place, publisher, year, edition, pages
Örebro: Örebro universitet, 2009. 68 p.
Series
Örebro Studies in Environmental Science, ISSN 1650-6278 ; 14
Keyword
amino acids, 13C, carbon cycle, ectomycorrhiza, elevated CO2, exudation, DOC, LMWOA, metal stress, monosaccharides, oxalate, Pinus sylvestris, saprotrophic fungi, soil respiration
National Category
Natural Sciences Environmental Sciences
Research subject
Enviromental Science
Identifiers
urn:nbn:se:oru:diva-11848 (URN)978-91-7668-692-8 (ISBN)
Public defence
2009-11-13, Hörsal HSM, Fakultetsgatan 1, Örebro, 11:15 (English)
Opponent
Supervisors
Available from: 2010-09-15 Created: 2010-09-15 Last updated: 2017-10-18Bibliographically approved
2. Organic complexing agents for remediation of heavy metal contaminated soil
Open this publication in new window or tab >>Organic complexing agents for remediation of heavy metal contaminated soil
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Soil washing of heavy metal contaminated soil may be enhanced by the addition of synthetic chelators. Since many of these chelators may imply stress to soil organisms and are poorly biodegraded, identification and evaluation of effective biodegradable or recyclable chelators (synthetic and/or naturally produced) is of great interest. The efficiency of biodegradable synthetic chelators was evaluated both in bench- (0.3 kg) and meso- (10 kg) scale. Results demonstrated that the solubilization of copper, lead, and zinc was similar in bench- and meso-scale systems, which indicated that these systems could be used in a technical scale. However, the arsenic extraction in meso-scale system, were non-conclusive. Due to the high cost involved in the purchase of synthetic chelating agents, recycling of the solutions is of great interest, and this was achieved in five consecutive washing cycles. Considering the economy of a full-scale process, recycling of complexing solutions with sulfide addition at each cycle, both at the 100 mM-level, appears feasible. Naturally derived chelators were produced by saprotrophic fungi and through alkaline degradation of humic substances and cellulose. The results demonstrated that these types of complexing agents are not as effective as the synthetic chelators. In the fungal systems, desorption of metals was related to production of organic complexing acids, but mainly to the pH-decrease. Nonetheless, in some systems, formation of soluble complexes was indicated (copper). Enhancement of copper, lead, and zinc release with the use of alkaline leachates from wood and peat appeared possible. Since these agents have a natural origin and are derived from rather cheap raw material, recycling is not an issue.

 

Place, publisher, year, edition, pages
Örebro: Örebro universitet, 2009. 59 p.
Series
Örebro Studies in Environmental Science, ISSN 1650-6278 ; 12
Keyword
soil washing, heavy metals, chelators, recycling
National Category
Natural Sciences Environmental Sciences
Research subject
Enviromental Science
Identifiers
urn:nbn:se:oru:diva-7913 (URN)978-91-7668-680-5 (ISBN)
Public defence
2009-10-02, HSP1, Fakultetsgatan 1, Örebro, 10:15 (English)
Opponent
Supervisors
Available from: 2009-09-11 Created: 2009-09-11 Last updated: 2017-10-18Bibliographically approved

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Arwidsson, ZandraJohansson, Emma M.Allard, Bertvan Hees, Patrick A. W.

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