THE VOLUMETRIC OXYGEN MASS-TRANSFER COEFFICIENT IN ANTIBIOTIC BIOSYNTHESIS LIQUIDS

This paper approaches the problem of oxygen mass transfer. This transfer is in antibiotic biosynthesis liquids produced by microorganisms belonging to the actinomycete and fungi classes, which exhibit a shear thinning non-Newtonian rheological behaviour. The volumetric oxygen mass transfer coefficients in these liquids (k(L)a(b)) change during biosynthesis processes. The change is mainly due to rheological parameter modifications, such as increasing the consistency index (K) and decreasing the flow behaviour index (n). The values of k(L)a(b) were 3.0-6.5 times lower than those recorded in water, and their decreasing depended on the k(L)a values obtained without biological liquid and on the nature of fermentation broths, as well. Starting from experimental data, two correlations were established between k(L)a(b) and P/V, upsilon(SG) and P/V, upsilon(SG), N, respectively. These correlations contain a dimensionless factor (eta(am)/eta(g))a6, which takes into account the rheological properties of the liquid phase and offers the possibility for a fast and sufficiently accurate estimation of k(L)a(b). The empirical correlations developed in the paper correspond reasonably well with the relatively wide variety of experimental data, as in the model proposed by PEREZ and SANDALL, and allow for the comparison of the fermentation batches of the same or different microorganisms; also, they may be applied to the workings of design, scale-up, control and monitoring of bioreactors.