Phenol degradation in a fixed‐bed bioreactor using micro‐cellular polymer‐immobilized Pseudomonas syringae

Abstract

Highly porous (85% void volume) polymer beads with interconnecting micro-pores were prepared for the immobilization of Pseudomonas syringae for the degradation of phenol in a fixedbed column bioreactor. The internal architecture of this support material (also known as PolyHIPE Polymer) could be controlled through processing before the polymerization stage. The transient and steady state phenol utilization rates were measured as a function of substrate solution flow rate and initial substrate concentration. The spatial concentration of the bacteria on the micro-porous support particles as well as within them was studied using scanning electron microscopy at various time intervals during the continuous operation of the bioreactor. It was found that although bacterial penetration into the porous support was present after 20 days, bacterial viability however, was compromised after 120 days as a result of the formation of a biofilm on the support particles. The steady state phenol utilization at an initial phenol concentration of 200 mg cm −3 was 100% provided that the flow rate was less than 7 cm 3 min −1 . Substrate inhibition at a constant flow rate of 4.5 cm 3 min −1 was found to begin at 720 mg dm −3 . The critical dilution rate for bacteria washout was high as a result of the highly hydrophobic nature of the support and the reduction of pore interconnect size due to bacterial growth within the pores in the vicinity of the surface of the support.

Bioprocess intensification in flow‐through monolithic microbioreactors with immobilized bacteria

“…A phenol degrading bacteria, Pseudomonas syringae (AEK1) was used in the packed-bed reactor (Akay et al, 2002a;Erhan et al, 2002Erhan et al, , 2004. P. syringae from stock cultures were seeded onto Petri dishes containing nutrient agar solid media and incubated for 48 h at room temperature.…”

“…There are various degradation studies using phenol and other aromatic compounds by free or immobilized microorganisms (Klein and Schara, 1981;Bettmann and Rehm, 1984;Schröder et al, 1996;Hecht et al, 2000;Erhan et al, 2004). Phenol has a highly toxic effect on all bacteria and there are various data reported on the inhibition effect of phenol for the growth of Pseudomonas sp.…”

“…Furthermore, the degradation of phenol is aerobic, and therefore presents a further challenge to the intensification of bioconversion. Recently, we also studied the degradation of phenol using immobilized enzymes (Akay et al, 2002a;Erhan et al, 2002) and immobilized bacteria (Erhan et al, 2004) using a microporous cell support system originally developed for animal cell support for tissue engineering applications (Akay et al, 2002bBokhari et al, 2003Bokhari et al, , 2005. Phenol degradation studies using immobilized Pseudomonas sp.…”

“…Phenol degradation studies using immobilized Pseudomonas sp. (Erhan et al, 2004) also provide us with a direct baseline to compare the BI achieved in the present study.…”

“…We have chosen phenol, for which the metabolic pathways are well described (Dagley, 1971;Buswell, 1975;Erhan et al, 2004), as a model substrate to conduct the continuous microbioreactor experiments. There are various degradation studies using phenol and other aromatic compounds by free or immobilized microorganisms (Klein and Schara, 1981;Bettmann and Rehm, 1984;Schröder et al, 1996;Hecht et al, 2000;Erhan et al, 2004).…”