Models for the Biodegradation Kinetics of Naphthalene by Ralstonia Eutropha

Abstract

Biodegradation of naphthalene (naph.) by a pure culture of Ralstonia eutropha was studied. Dissolution of naph. in aqueous solution was provided by using Tween-80 nonionic surfactant. By developing the solubility curve, the molar solubility ratio (MSR) was determined (0.8081). The effects of Tween-80, initial-pH, and naph. concentration on the R. eutropha growth and its naph. degradation capability were investigated. Degradation of naph. at 50 mg/L was complete within 52 h in the presence of 1.6 mM Tween-80 at pH 7. Haldane, Webb, Aiba, and Edwards, as the growth inhibitory kinetic models, were used to mathematically describe the inhibitory characteristic of naphthalene and the results were evaluated using nonlinear regression technique. The values of root mean square error (RMSE) and the correlation coefficient (R²) showed appropriateness of approach taken in the present study (RMSE≈ 3×10⁻³, R²≈ 0.99). Importance of the mechanistic view of these types of mathematical models has been emphasized.

Key Words:

• biodegradation
• kinetic models
• naphthalene
• Ralstonia eutropha
• substrate inhibition
• Tween-80