Effect of fluiddynamic conditions on growth rate and biodesulfurization capacity of Rhodococcus erythropolis IGTS8

摘要

The growth rate and desulfurization capacity accumulated by the cells during the growth of Rhodococcus erythropolis IGTS8 under different fluid dynamic conditions in a stirred and sparged tank bioreactor have been studied. Hydrodynamic conditions were changed using different stirrer speeds and gas flow rates. It was observed that the growth was strongly dependent on the stirrer speed employed. Oxygen transfer limitation was observed at low stirrer speeds (from 100 to 250 rpm). In contrast, at higher stirrer speeds, cell damage was caused by hydrodynamic stress in the turbulent bulk of the broth, yielding again a decrease in growth for stirrer speeds higher than 450 rpm. Moreover, increasing the agitation from 100 to 450 rpm has a positive influence on the development of the desulfurization capacity of the cells during growth, yet this capacity shows a dramatic decrease for higher stirrer speeds. Nevertheless, the change of the air flow rate hardly has any influence on the growth rate and no hydrodynamic stress effect has been detected between 1 and 10 Lmin(-1). A regime analysis of the characteristic times for oxygen mass transfer, oxygen uptake and mixing under different agitation conditions has been made. It was found that the minimum stirrer speed necessary for a satisfactory performance of the bioreactor from the point of view of the cells oxygen demand was 350 rpm, while at stirrer speeds over 450 rpm, growth rate and desulfurization capacity are both negatively affected. (C) 2015 Elsevier B.V. All rights reserved.