Statistical modelling and optimization of medium for toluene degradation by Brevibacillus parabrevis ATHH40 immobilized cells

ABSTRACT

Response surface methodology was used to optimise toluene degradation by immobilised Brevibacillus parabrevis ATHH40. The pH, temperature and toluene concentration were the most significant factors in toluene degradation. Central composite design was applied to determine optimal concentrations of these factors and the effect of their mutual interactions. The interaction between pH and temperature with toluene concentration was found to enhance toluene degradation, whereas pH, temperature and toluene concentration exhibited an independent influence. Using statistical optimisation, a maximum toluene degradation was achieved when pH, temperature and toluene concentration were adjusted to 6.93, 34.76°C and 774.76 mg L⁻¹. This optimised medium was employed for toluene degradation by Brevibacillus parabrevis immobilised by multi-walled carbon nanotubes that improved toluene degradation to 93.87%, much higher than achieved by cultures of free cells.

KEYWORDS:

• Toluene degradation
• optimisation
• response surface methodology

Acknowledgments

The authors thank the Soil Science Department, Isfahan (Khorasgan) Branch, Islamic Azad University, Isfahan for support and funding of this research.

Disclosure statement

Soil Science Department, Isfahan (Khorasgan) Branch, Islamic Azad University, Isfahan for supporting the study as part of the first author’s PhD thesis and allowing the researchers to conduct this study.