Decoupling of oxygen transfer and power dissipation for the study of the production of pristinamycins by Streptomyces pristinaespiralis in shaking flasks
Résumé
Streptomyces pristinaespiralis is a filamentous bacterium used in the pharmaceutical industry for the production of pristinamycins. In previous works, it was shown that the occurrence of production and the antibiotics concentration could be related to gas-liquid transfer and power dissipation in shaking flasks. Nevertheless, in standard cultures, both mechanisms are coupled. It is then a difficult task to assign a precise physiological response to either oxygen transfer or power dissipation. The aim of the present study was to decouple the oxygen transfer coefficient (k(L)a) and the power dissipation per unit of volume (Ply) to study their respective impact on pristinamycin production. During cultures in flasks, the rotation diameter of the shaking table was changed to modify the k(L)a but not the power dissipation P/V. The influence of operating conditions with P/V ranging from 0.55 to 10.3 kW m(-3) and k(L)a ranging from 30 to 490 h(-1) have been determined on the microbial kinetics and also on the pellet diameters. The final biomass concentration and the release of antibiotics were then related to k(L)a, whereas the final pristinamycins concentrations, as well as the bacterial pellet diameter were mainly correlated to P/V independently of the k(L)a. The change in the pellet diameter could be the crucial parameter for the pristinamycins production as it might influence the nutriment transfer inside the pellets and the ratio of active cells in each pellet.