Production of polyhydroxyalkanoates by Pseudomonas nitroreducens

Area of Science:

• Microbial biotechnology
• Polymer science
• Environmental microbiology

Background:

• Polyhydroxyalkanoates (PHA) are biodegradable polyesters synthesized by microorganisms.
• Pseudomonas species are known for their metabolic versatility and potential in biopolymer production.
• Isolation of novel microbial strains from contaminated environments can yield unique metabolic capabilities.

Purpose of the Study:

• To characterize the polyhydroxyalkanoate (PHA) synthesis capabilities of a newly isolated bacterial strain.
• To investigate the influence of different carbon sources and environmental conditions on PHA composition.
• To identify the types of monomers incorporated into the PHA polyester produced by the strain.

Main Methods:

• Isolation and identification of a bacterial strain (AS 1.2343) from oil-contaminated soil.
• Cultivation of the strain using various fatty acids (hexanoate, octanoate, butyrate, decanoate, lauric acid, tetradecanoic acid) as sole carbon sources.
• Analysis of PHA accumulation and composition using techniques such as gas chromatography and nuclear magnetic resonance spectroscopy.

Main Results:

• The isolated strain was identified as Pseudomonas nitroreducens AS 1.2343.
• The bacterium synthesized polyhydroxybutyrate (PHB) homopolymer from medium-chain-length fatty acids (hexanoate, octanoate).
• When using substrates like butyrate, decanoate, lauric acid, and tetradecanoic acid, PHA composed of medium-chain-length hydroxyalkanoate (HA) monomers (e.g., hydroxyoctanoate, hydroxydecanoate) were major components, reaching up to 77% of cell dry weight with lauric acid.
• Varying the carbon to nitrogen ratio significantly altered PHA monomer content, with a decrease in HB content as C/N increased.
• The PHA produced was a blend of acetone-insoluble PHB and acetone-soluble medium-chain-length HA monomers.

Conclusions:

• Pseudomonas nitroreducens AS 1.2343 exhibits a unique ability to synthesize diverse PHA polyesters.
• The composition of PHA can be tailored by manipulating the carbon source and C/N ratio in the growth medium.
• This strain holds potential for the production of specific PHA copolymers for various applications.