Ac. Badino et al., Volumetric oxygen transfer coefficients (k(L)a) in batch cultivations involving non-Newtonian broths, BIOCH ENG J, 8(2), 2001, pp. 111-119
The oxygen transfer in non-Newtonian fermentation broths of Aspergillus awa
mori, during batch cultivations in conventional 101 bioreactor has been inv
estigated. Values of the volumetric oxygen transfer coefficient (k(L)a), ob
tained at various impeller speeds, air flow rates and at distinct initial s
ubstrate concentrations were correlated with operational variables, geometr
ic parameters of the system and physical properties of the broths utilising
rigorous techniques in order to obtain a set of reliable and accurate data
. An experimental device was constructed for on-line rheological measuremen
ts, and the apparent dynamic viscosity was determined from the broth rheogr
ams. In order to measure power requirements, a torque meter was developed a
nd non-Newtonian fluids with rheological characteristics similar to the Asp
ergillus fermented broths were utilised to obtain reference curves and corr
elations in the fermentor where the cultivations took place. Gas balancing
method and a modified dynamic method were utilised simultaneously to determ
ine k(L)a values. The rigorous methods thus developed allowed adequate eval
uation of the oxygen transfer in the cultivations and also permitted good f
its of four different traditional correlations for k(L)a to the experimenta
l data. (C) 2001 Elsevier Science B.V. All rights reserved.