Biodesulfurization of dibenzothiophene by resting cells of Pseudomonas putidaCECT5279: influence of the oxygen transfer rate in the scale‐up from shaken flask to stirred tank reactor

Abstract

BACKGROUND In this work, the scale‐up of the biodesulfurization process at rest from shaken flask to stirred tank bioreactor cells has been studied taking into account the influence of the hydrodynamic conditions of the oxygen transfer rate. RESULTS Different hydrodynamic conditions to carry out the biodesulfurization in a stirred tank bioreactor have been studied and compared with the results obtained in a shaken flask. The best results were obtained at a stirrer speed of 400 rpm and an air flow rate of 2 vvm. The oxygen transfer rate has been found to be the rate‐limiting step, and there is a critical value, determined by a value for the volumetric mass transfer coefficient (kLa) of around 1.4 × 10−2 s−1, which cannot be exceeded without affecting the biodesulfurization process. CONCLUSION The 4S biodesulfurization pathway is highly sensitive to oxygen availability, even under oxygen limiting conditions. Results obtained in a shaken flask have been reproduced satisfactorily in a stirred tank bioreactor by combining different hydrodynamic conditions and the constant‐kLa scale‐up criterion has been used to validate this approach. © 2014 Society of Chemical Industry

Behavior of several pseudomonas putida strains growth under different agitation and oxygen supply conditions

“…Since DBT is not present in the cultures, and thus the 4S route is inoperative during the cultures, the experimental observations in GMO strains under low agitation conditions are not derived by the activity of the enzymes encoded in plasmid pESOX3. It has been reported that the presence of DBT reduces the toxicity of hydrogen peroxide, due to the performance of the 4S route in resting cells . Similar effects derived of the presence of H 2 O 2 in Pseudomonas cultures have been previously reported .…”

“…In the experiments carried out with the strain KTH2 (pESOX3), 0.025 g L −1 of tetracycline have to be added into LB or BSM medium, to prevent the loss of the operon dszABC ‐containing plasmid. The induction of the plasmid‐encoded genes was accomplished by adding 2 × 10 −6 g L −1 of IPTG before STBR inoculation …”

“…Firstly, the optimal cell age was established and the enhancing of the process by addition of co‐substrates was evaluated . Subsequently, a kinetic model was proposed in order to describe the experimental results and the influence of OTR over the biomass growth and the desulfurization capacity was studied, by changing the agitation or the airflow rate …”

“…10 Subsequently, a kinetic model was proposed in order to describe the experimental results and the influence of OTR over the biomass growth and the desulfurization capacity was studied, by changing the agitation or the airflow rate. 4,25 The results showed that, if the culture is carried out at a high agitation, which induces high dissolved oxygen concentration, the growth rate increases and the cells are not affected by shear stress. However, the desulfurization capacity operating with resting cells present a dramatic decrease when the cells are exposed to a stirrer speed higher than 300 rpm.…”

Desulfurization of Dibenzothiophene by Pseudomonas fluorescens (UCP 1514) Leading to the Production of Biphenyl

“…at 30°C [21]. Martinez et al [22] studied the biodesulfurization of dibenzothiophene by resting cells of Pseudomonas putida CECT5279, where complete conversion into HBP was reached in 90 min, using a gas flow of 2 vvm, thus…”