Biodegradation mechanism of biphenyl by a strain of Pseudomonas stutzeri

Abstract

The mechanism of biphenyl biodegradation by Pseudomonas stutzeri was studied. Growth curves on biphenyl were measured, along with dissolution kinetics of biphenyl and production of biosurfactants by the bacterium. Biphenyl was supplied as pure crystals (the crystal biphenyl), adsorbed to Chromosorb G (the Chromosorb G biphenyl) or XAD-4 particles (the XAD-4 biphenyl). No lag phase was observed on the crystal biphenyl, while this period lasted 3.5–6.0 hours on the Chromosorb G biphenyl. The linear specific growth rates (LSGRs) ranged from 2.00 × 10⁻⁴ to 293 × 10⁻⁴ dry weight grams/L/h (d.w.g/L/h) on these two substrates. The LSGR values were directly proportional to the interfacial area between the solid substrate and the microbial suspension. The XAD-4 biphenyl was not bioavailable to the bacterium. The zero-order rates of dissolution ranged from 2.3 × 10⁻⁵to 8.0 × 10⁻⁴ g/L/h on the crystal biphenyl and the Chromosorb G biphenyl. No biosurfactant production was observed on any biphenyl substrate. Growth curves, results of dissolution measurements and the scanning electron microscope (SEM) images indicate that Pseudomonas stutzeri takes up biphenyl from the aqueous phase as well as the solid phase of the crystal and the Chromosorb G biphenyl. The mechanism of uptake depends on the initial biphenyl concentration and the particle diameter of the biphenyl substrate.

Keywords:

• Biphenyl
• biodegradation
• Chromosorb G
• XAD-4
• Pseudomonas stutzeri

Acknowledgments

Although the research described in this article has been funded in part by the United States Environmental Protection Agency (grant number R82-6652-011), it has not been subjected to the Agency's required peer and policy review and therefore does not necessarily reflect the views of the Agency and no official endorsement should be inferred.