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Interaction between poly-3-hydroxybutyrate-co-3-hydroxyvalerate and a denitrifying Pseudomonas strain
J Biedermann1, A J Owen, K T Schloe
1Universität Hohenheim, Institut für Mikrobiologie, Stuttgart, Germany. biederma@uni-hohenheim.de
Canadian Journal of Microbiology
|June 1, 1997
Summary
Different lots of poly-3-hydroxybutyrate-co-3-hydroxyvalerate (P(HB-co-HV)) affected microbial denitrification. Plasticizers like triacetine inhibited growth, while polymer hydrophobicity influenced bacterial adhesion and degradation efficiency.
Area of Science:
- Environmental microbiology
- Biotechnology
- Polymer science
Background:
- Heterotrophic denitrification is crucial for nitrogen removal in wastewater treatment.
- Polyhydroxyalkanoates (PHAs) like P(HB-co-HV) are biodegradable polymers with potential as carbon sources in bioreactors.
- Variability in commercial PHA lots may impact microbial processes.
Purpose of the Study:
- To investigate how physical and chemical properties of commercial P(HB-co-HV) affect biofilm formation and metabolic activity of a denitrifying starter culture.
- To assess the suitability of P(HB-co-HV) as a matrix substance in heterotrophic denitrification reactors.
- To identify factors influencing the performance of P(HB-co-HV) in microbial denitrification.
Main Methods:
- Laboratory-scale heterotrophic denitrification reactor experiments.
- Characterization of different lots of P(HB-co-HV) (Biopol).
- Assessing bacterial adhesion (Pseudomonas sp. strain 2nIII) and polymer degradation.
- Analysis of chemical additives (e.g., triacetine) and polymer composition (hydroxyvaleric acid content).
Main Results:
- No significant differences in P(HB-co-HV) microstructure were observed between lots.
- Triacetine, a plasticizer in most lots, exhibited growth inhibitory effects on the starter culture.
- Bacterial adhesion varied, with Pseudomonas sp. strain 2nIII showing better adsorption to hydrophobic polymers.
- Pseudomonas sp. strain 2nIII degraded poly-3-hydroxybutyrate homopolymer and P(HB-co-HV) copolymers but not poly-3-hydroxyvaleric acid.
Conclusions:
- The suitability of P(HB-co-HV) for denitrification depends on its chemical additives and physical properties influencing bacterial adhesion.
- Triacetine contamination is a critical factor limiting the effectiveness of P(HB-co-HV) as a carbon source.
- Substrate specificity of polyhydroxyalkanoate depolymerase likely explains the differential degradation of PHA polymers.