## Results and Discussion
\begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \(Gly_{0}\) & \multicolumn{3}{c}{**Time**} & \(Gly_{0}\) & \(X\) & \(\rm MI\) & \(\rm Ery\) & \(\rm Ara\) & \(CA\) & \(Pol\) & \(Y_{CA/Gly}\) & \(\rm Y_{Pol/Gly}\) \\ (g/L) & & **(h)** & **(g/L)** & **(g/L)** & **(g/L)** & **(g/L)** & **(g/L)** & **(g/L)** & **(g/L)** & **(g/L)** & **(g/g)** & **(g/g)** \\ \hline \(\approx\)100 Flasks & \(\pm\)0 & 183 & 95.4 \(\pm\) 7.1 & 15.0 \(\pm\) 1.9 & 13.8 \(\pm\) 2.2 & 17.1 \(\pm\) 2.5 & 7.3 \(\pm\) 1.2 & - & 38.2 \(\pm\) 5.9 & - & 0.40 \\ \hline \(\approx\)100 & \(\pm\)0 & 4.5 & 86.8 \(\pm\) 6.1 & 21.0 \(\pm\) 3.1 & 3.0 \(\pm\) 0.5 & - & - & 20.4 \(\pm\) 3.3 & 3.0 \(\pm\) 0.5 & 0.24 & 0.03 \\ Bioreactor & b & 65 & 103.5 \(\pm\) 9.9 & 19.0 \(\pm\) 3.4 & 0.5 \(\pm\) 0.1 & - & - & 42.4 \(\pm\) 5.5 & 0.5 \(\pm\) 0.1 & 0.41 & 0.004 \\ \hline \end{tabular}
\end{table} 
Table 3: Quantitative data of cultures of _Yarrowia lipolytica_ LMBF Y-46 on glycerol-based media in which initial glycerol concentration (\(Gly_{0}\)) \(\approx\) 100 g/L was added (nitrogen was added as ammonium sulfate at 2.0 g/L and yeast extract at 3.0 g/L) in shake-flask and batch bioreactor experiments. Culture conditions: for the flask experiment as in Table 1. For the bioreactor experiment: agitation \(800\pm 5\) rpm, pH = 6.0 \(\pm\) 0.1, aeration fluctuating from 0.1 up to 2.0 vvm in order to have a DOT \(\geq\) 10% \(\%\)/, incubation temperature \(T=28\pm 1\)\({}^{\circ}\)C, active volume = 2.0 L. Culture details when the maximum concentration of polyols (\(Pol\), g/L) (a), citric acid (CA, g/L) (b) and yeast dry cell biomass (\(X\), g/L) (c) was achieved. MI, Ery and Ara is the concentration of mannitol, erythritol and arabitol, respectively (in g/L), at the given fermentation times. Each experimental point presented is the mean value of two independent determinations. The most profound difference between the flask and the bioreactor trial was observed in the spectrum of the final fermentation products between the two cultures; in the shake-flask trial (and despite the fact that pH was \(>\)4.5--as previously stated in most of the shake-flask experiments pH value was found within the range 4.8-5.8) the major metabolites synthesized were the three previously indicated polyols (_Pol_ = 38.2 g/L, \(Y_{Pol|Gly_{0}}\) = 0.40 g/g). In contrast, a remarkable metabolic shift in which mostly citric acid was produced occurred in the bioreactor experiment. Specifically, a \(CA_{\text{max}}\) quantity = 42.4 g/L (simultaneous \(Y_{CA/Gly}\) = 0.41 g/g) was reported, whereas insignificant quantities of mannitol and negligible ones or aribitol and erythroid were reported in the batch bioreactor experiment (Table 3). Iso-citric acid quantity ranged between 5-9% of the total citric acid concentration determined. In the above-mentioned fermentation point, iso-citric acid corresponded to 8.0% _w/w_ of \(CA\) formed. Moreover, it is interesting to indicate that the maximum volumetric productivity of \(CA\) (\(P_{CA\text{max}}\)) achieved in the current batch culture (\(P_{CA\text{max}}\) calculated as \(P_{CA\text{max}}=\frac{CA_{\text{max}}}{\Delta t}\), where \(\Delta t\) is the fermentation time in the batch or fed-batch culture requested to achieve this \(CA_{\text{max}}\) value) was \(\approx\)0.65 g/L/h, being certainly comparable with the highest values reported by other wild-type or mutant _Y. lipolytica_ strains cultivated in batch (0.52-0.85 g/L/h [55]), fed-batch (i.e., 0.40-0.93 g/L/h [56, 57, 58, 59]), and continuous (between 0.70 and 1.30 g/L/h [60]) bioreactor operations (in the cited batch and fed-batch cultures, \(P_{CA\text{max}}\) was calculated as in the present study, whereas in the continuous cultures, \(P_{CA}\) was calculated as \(P_{CA}=CA\cdot D\), where \(CA\) was the concentration at the steady-state and \(D\) was the dilution rate imposed).