Formaldehyde degradation by Ralstonia eutropha in an immobilized cell bioreactor

Abstract

The formaldehyde (FA) degradation ability of the loofa-immobilized Ralstonia eutropha cells in a packed bed reactor was modeled using a statistically based design of the experiment (DOE) considering application of response surface methodology (RSM). The simultaneous effects of four operative test factors on the cells performance in terms of FA degradation rate and extent of the chemical oxygen demand (COD) removal were monitored. The combination of factors at initial FA concentration of 629.7 mg L⁻¹h⁻¹, recycling substrate flow rate of 4.4 mL min⁻¹, aeration rate of 1.05 vvm, and the system's temperature of 28.8°C resulted the optimal conditions for the FA biodegradation rate and COD removal efficiency. Loofa porous structure was found to be a protective environment for the cells in exposing to the toxic substances and the scanning electron microscopy (SEM) images revealed extensive cells penetration within this support. Oxygen transfer analysis in the form of evaluating K _la value was also carried out and at the optimum conditions of the DOE was equaled to 9.96 h⁻¹and oxygen uptake rate was 35.6 mg L⁻¹h⁻¹.

Keywords:

• Ralstonia eutropha
• formaldehyde degradative ability
• loofa sponge
• factorial centered central composite design
• volumetric mass transfer coefficient