Figure 2: Optimization of TAG production from xylose by R. opacus MITXM-61 in batch-culture fermentations. (a) Central composite experimental design matrix defined xylose and (NH4)2SO4 concentrations. X1, xylose concentration (gl-1); X2, (NH4)2SO4 concentration (gl-1). The strain was grown in modified defined media containing various concentrations of xylose and (NH4)2SO4 in Sixfors-bioreactors. The data for TAG production as fatty acids represent the maximum values during 10 days of cultivation. (b) Response surface plot of the effect of xylose and (NH4)2SO4 concentrations on fatty acid production. Curves and points represent predicted values and experimental data, respectively. (c) Time course of fatty acid production carried out under the optimized growth conditions in Sixfors-bioreactor cultivations. The strain was grown in a modified defined medium containing 159 gl-1 xylose and 9.63 gl-1 (NH4)2SO4. Values and error bars represent the mean and s.d. of triplicate experiments.