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Metal uptake by microalgae: Underlying mechanisms and practical applications

Authors

  • Cristina M. Monteiro,

    1. CBQF/Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Rua Dr. António Bernardino de Almeida, P-4200-072 Porto, Portugal
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  • Paula M. L. Castro,

    1. CBQF/Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Rua Dr. António Bernardino de Almeida, P-4200-072 Porto, Portugal
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  • F. Xavier Malcata

    Corresponding author
    1. ISMAI—Instituto Superior da Maia, Avenida Carlos Oliveira Campos, Castelo da Maia, P-4475-690 Avioso S. Pedro, Portugal
    2. CIMAR/CIIMAR—Centro Interdisciplinar de Investigação Marinha e Ambiental, Rua dos Bragas n° 289, P-4050-123 Porto, Portugal
    3. Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Avenida da República, P-2780-157 Oeiras, Portugal
    • ISMAI—Instituto Superior da Maia, Avenida Carlos Oliveira Campos, Castelo da Maia, P-4475-690 Avioso S. Pedro, Portugal
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Abstract

Metal contamination of a few aquatic, atmospheric, and soil ecosystems has increased ever since the industrial revolution, owing to discharge of such elements via the effluents of some industrial facilities. Their presence to excessive levels in the environment will eventually lead to serious health problems in higher animals owing to accumulation throughout the food web. Current physicochemical methods available for recovery of metal pollutants (e.g., chemical precipitation, oxidation/reduction, or physical ion exchange) are either expensive or inefficient when they are present at very low concentrations. Consequently, removal of toxic metals by microorganisms has emerged as a potentially more economical alternative. Microalgae (in terms of both living and nonliving biomass) are an example of microorganisms suitable to recover metals and able to attain noteworthy percent removals. Their relatively high metal-binding capacities arise from the intrinsic composition of their cell walls, which contain negatively charged functional groups. Consequently, microalgal cells are particularly efficient in uptake of those contaminants when at low levels. Self-defense mechanisms developed by microalgal cells to survive in metal-containing media and environmental factors that affect their removal (e.g., pH, temperature, and biomass concentration) are reviewed here in a comprehensive way and further discussed in attempts to rationalize this form of remediation vis-a-vis with conventional nonbiological alternatives. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2012

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