BIOVAB: Evaluation of bacterial strategies to promote bioavailability of hydrophobic pollutants for efficient bioremedation of contaminated soils

• Forschungsstelle: EU FRP
• Projektnummer: 96.0404
• Projekttitel Englisch: BIOVAB: Evaluation of bacterial strategies to promote bioavailability of hydrophobic pollutants for efficient bioremedation of contaminated soils

Schlüsselwörter (Englisch)

Bacteria; bacterial strategies; bioavailability; biofilm; bioremediation; growth kinetics; mass transfer limitation; modeling; mycobacterium; PAH

Alternative Projektnummern (Englisch)

EU project number: BIO4-CT97-2015

Forschungsprogramme (Englisch)

EU-programme: 4. Frame Research Programme - 4.1 Biotechnology

Kurzbeschreibung (Englisch)

See abstract

Partner und Internationale Organisationen (Englisch)

Vlaams Institute voor Technologisch Onderzoek, Mol (B), Catholic University of Louvain, Bruxelles (B), University of Amsterdam (NL), National Environmental Research Institute, Roskilde (DK), Technical University of Munich, Garching (D), Instituto de Recursos Naturales y Agrobiologia, Sevilla (E), A/S Bioteknisk Jordrens, Kalundborg (DK)

Abstract (Englisch)

The low bioavailability of hydrophobic organic contaminants (HOC) is considered one of the major bottlenecks for further progress in soil bioremediation technology. HOC, such as polycyclic aromatic hydrocarbons (PAH) are poorly accessible to microbial attack because they are sorbed to solid soil constituents or dissolved in non-aqueous phase liquids. As bacteria appear to degrade chemicals only when they are dissolved in water, physically retarded HOC-transfer to the aqueous phase combined with an unequal spatial distribution of microorganisms and HOC often results in limited efficiency of in-situ soil bioremediation. Whereas bioavailability-promoting engineering solutions have been intensively studied, few was known about the pollutant mass transfer-enhancing strategies of the principal catalysts in bioremediation, the bacteria themselves. Experimental evidence and theoretical considerations indicated that the utilization of PAH in soil would require bioavailability-enhancing strategies of the bacteria such as (i) biosurfactant excretion, (ii) exposure of cell surface structures with emulsifying properties, (iii) high affinity uptake systems, and (or) (iv) adhesion to the solid or liquid substrates. In the present project, anthracene-degrading Mycobacterium sp. LB501T was studied for the possible employment of such strategies. This bacterial strain was isolated in cooperation with our Belgian project partner from PAH-contaminated soil by applying a new Teflon membrane-based extraction method that promotes hydrophobic bacteria likely to adhere to hydrophobic surfaces. When poorly soluble solid anthracene served as sole carbon source in batch cultures, M. sp. LB501T grew as a biofilm on the crystals. However, no significant biofilm formation was detected when better available substrates such as crystalline phenanthrene or anthracene in the presence of glucose were present. This difference was attributed to a surface modification of the bacteria. In static (batch) and dynamic (column) adhesion experiments, anthracene-grown cells exhibited significantly better adhesion to anthracene crystals and hydrophobic surfaces (Teflon) than glucose-grown cells. Little adhesion of anthracene-grown cells to likewise hydrophobic phenanthrene crystals was observed. Additionally, a high specific affinity and low requirements for cell maintenance were found, but no production of surface-active compounds. The influence of the substrate was further confirmed by an analysis of mycolic acids (components of the outer cell wall) of M. sp. LB501T. PAH grown cultures exhibited later eluting, more hydrophobic mycolic acids, which are a likely cause for their increased adhesion efficiency to more hydrophobic surfaces. Our results furthermore indicate that M. sp. LB501T is specialized in the utilization of anthracene by being extremely oligotrophic. Besides its physiological adaptation to low substrate availability, M. sp. LB501T seems to have responded to the fact that their substrates are hydrophobic and enrich in hydrophobic phases rather than being dissolved in the soil water. The observation that this strain tends to attach to HOC crystals only when the substrate flux is low indicates that attachment is an actively regulated strategy to optimize substrate bioavailability.

Datenbankreferenzen (Englisch)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 96.0404