Oxygen transfer in broths of plant cells at high density.
The rheological properties of the culture broths of some plant cells (Cudrania tricuspidata, Vinca rosea, and Agrostemma githago) at high density (10-18 g dry wt/L) were measured, and oxygen transfer in the broths in various bioreactors was investigated. The rheological properties of the broths were dependent on the size, specific gravity, and concentration of the cell aggregates contained in the broths. The broths were non-Newtonian and pseudoplastic fluids. The flow behavior index n was fairly constant (0.53) and the consistency index K varied in proportion to the sixth-to-seventh power of the cell mass concentration M. The apparent viscosity mu(a) of the broths was in proportion to the 6.5th power of M. The oxygen transfer in the broths was discussed on the basis of the results obtained for suspensions of granulated agars (agar concentration, 5.8%) in water, which were similar to the broths in rheological properties. The volumetric oxygen transfer coefficient k(L)a in the broths was dependent on mu(a)(k(L)a proportional, variant mu(a) (-m)) and decreased greatly at a certain apparent viscosity, mu(ac). The values of m and mu(ac) were closely related to the aeration-agitation mechanisms of the bioreactors. The values of mu(ac) in aeration-agitation type bioreactors was larger than that in aeration-type bioreactors, whereas for m, the reverse was true.
Tanaka
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Institute of Applied Biochemistry, University of Tsukuba, Ibaraki, Japan.