首页|Oxygen transfer and bubble sizes occurring in a pilot‐scale cultivation of Bacillus velezensis 83 for the production of poly(γ‐glutamic acid) under two schemes of power drawn
Oxygen transfer and bubble sizes occurring in a pilot‐scale cultivation of Bacillus velezensis 83 for the production of poly(γ‐glutamic acid) under two schemes of power drawn
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NSTL
Wiley
Abstract BACKGROUND The influence of power consumption on oxygen transfer during non‐Newtonian and surfactant‐producing microbial fermentations has been scarcely reported. In this work, we study the oxygen transfer and bubble size distributions in a real 100?L fermentation (producing poly(γ‐glutamic acid)) occurring under constant stirring speed (N) and under constant retrofitted power drawn (Pg/V). RESULTS For constant N fermentations, Pg/V and the volumetric mass transfer coefficient (kLa) decreased 40% and 70% during cultivation, respectively. Fermentations at constant Pg/V showed a decrease similar to that observed for constant N fermentations. Bubble size distributions were also similar for both operational conditions. Although an increase in bubble size was expected at constant N cultivations due to the increasing viscosity of the medium, the Sauter mean diameter (d32) decreased 65%. This singular behavior of d32 was likely caused by surfactin and bacillomycin, metabolites with strong surfactant activity produced by Bacillus velezensis 83 in the cultivations. The use of a constant Pg/V did not counteract the decrease in kLa due to the increase in viscosity. Although the presence of biosurfactants leads to an increase of interfacial transfer area by decreasing d32, the presence of these molecules and the increase in the medium viscosity affected kLa. CONCLUSIONS An atypical behavior of this system was found, especially in d32, different to that based on common correlations found in the literature. A complex interaction among the multiple factors involved in a real bioprocess for poly(γ‐glutamic acid) production was evidenced. ? 2022 Society of Chemical Industry (SCI).
Power drawnoxygen transferbubble sizespoly(γ‐glutamic acid)
NSTL
Wiley
