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Keywords:

  • biopolymers;
  • hazardous waste;
  • pseudomonads

Abstract

Aims

The aim of this study was to convert numerous polyaromatic and monoaromatic hydrocarbons into biodegradable polymer medium-chain-length polyhydroxyalkanoate (mcl-PHA).

Methods and Results

Using naphthalene enrichment cultivation method, we have isolated seven bacterial strains from the river sediment exposed to petrochemical industry effluents. In addition to naphthalene, all seven strains could utilize between 12 and 17 different aromatic substrates, including toluene, benzene and biphenyl. Only one isolate that was identified as Pseudomonas sp. TN301 could accumulate mcl-PHA from naphthalene to 23% of cell dry weight. Owing to poor solubility, a method of supplying highly hydrophobic polyaromatic hydrocarbons to a culture medium was developed. The best biomass and mcl-PHA yields were achieved with the addition of synthetic surfactant Tween 80 (0·5 g l−1). We have shown that Pseudomonas sp. TN301 can accumulate mcl-PHA from a wide range of polyaromatic and monoaromatic hydrocarbons, and mixtures thereof, while it could also accumulate polyphosphates and was tolerant to the presence of heavy metal (100 mmol l−1 cadmium and 20 mmol l−1 nickel).

Conclusions

A new Pseudomonas strain was isolated and identified with the ability to accumulate mcl-PHA from a variety of aromatic hydrocarbons.

Significance and Impact of the Study

This study is the first report on the ability of a bacterial strain to convert a range of polyaromatic hydrocarbon compounds to the biodegradable polymer (mcl-PHA). Mcl-PHA is gaining importance as a promising biodegradable thermoelastomer, and therefore, isolation of new producing strains is highly significant. Furthermore, this strain has the ability to utilize a range of hydrocarbons, which often occur as mixtures and could potentially be employed in the recently described efforts to convert waste materials to PHA.