[Kinetic model of micro-organism growth: the case of Xanthomonas campestris]

Microbial growth is studied and kinetic models to describe the process rate useful in the scale-up are proposed. The growth of Xanthomonas campestris NRRL B-1459, a bacterium producing xanthan, a major industrial gum, is studied. Experimental data are arranged by means of different methods, and linear and non-linear regression techniques are applied in several ways (i.e. fixing or not fixing the values of certain parameters) and they are compared. To obtain parameter values with statistical meaning, two parameters must be calculated (namely, the maximum specific growth rate and the maximum biomass concentration available) by means of a non-linear regression technique employing the logistic equation. The maximum specific growth rate is related to temperature by means of different equations, but that of Ratkowsky et al. is the most suitable for X. campestris growth. Studied variables present no tendency to error and the reproduction of experimental data is very good.