## Materials and Methods
### Analyses  
In order to proceed to the various analyses, the whole content of the flasks (\(\approx\)46-48 mL) or a sample \(\approx\)20 mL of the bioreactor experiments was collected. In the case of the shake-flask trials, due to slight water evaporation, the volume of the liquid medium in the flasks after harvesting was \(47\pm 1\) mL. Certainly, the more the culture duration was elevated, the more water evaporation of the medium occurred. Nevertheless, the volume of the medium was never lower than 46 mL. This volume was always corrected to 50 mL and the whole content of the flask was used in the performed analyses. Regardless of the volume of the sample, yeast cells were harvested by centrifugation, and yeast total biomass quantity was determined through its dry cell weight (DCW, g/L) [16; 21]. Non-consumed glycerol (_Gly_), citric acids (citric + iso-citric acid) (_CA_), mannitol (MI), arabitol (Ara) and erythroid (Ery) were determined with the aid of HPLC analysis [18; 22]. In several fermentation points, iso-citric was assayed according to [PERSON] et al. [23]. Cellular lipids were extracted from the yeast DCWaccording to the modified \"Folch\" method [16; 24], while total microbial oil was recovered and trans-esterified according to [PERSON] et al. [24]. The produced fatty acid methyl-esters (FAMEs) were suspended in hexane and analyzed by GC analysis in a Varian CP-3800 chromatograph equipped with flame ionization detector (Agilent Technologies, Santa Clara, CA, USA), in which an Agilent J&W Scientific DB23 capillary column (model n.123-2332, 30.0 m \(\times\) 0.32 mm, film thickness 0.25 \(\upmu\)m) (Agilent Technologies, Santa Clara, CA, USA) was used. Helium gas was used as a carrier gas with a column flow rate of 2.0 mL/min. The set up conditions were as follows: initial oven temperature was set at \(T\) = 150 \({}^{\circ}\)C, held for 18 min, subsequently rammed to \(T\) = 185 \({}^{\circ}\)C at a rate of 5 \({}^{\circ}\)C/min and held for 2 min. Then the oven temperature was moved to \(T\) = 210 \({}^{\circ}\)C at a flow rate of 5 \({}^{\circ}\)C/min and held for 2 min, then increased to \(T\) = 240 \({}^{\circ}\)C at 10 \({}^{\circ}\)C/min. The injector and flame ionization detector temperatures were set at \(T\) = 260 \({}^{\circ}\)C and \(T\) = 270 \({}^{\circ}\)C, respectively. Individual FAMEs were identified by comparison of their retention times with external standard (Supelco 37 Component FAME Mix, CRM47885) retention times. The amounts of individual FAMEs identified were expressed in % of the total fatty acid areas chromatograms identified. In the case of the shake-flask cultures and for various fermentation points, the DOT was determined according to the procedure proposed in [PERSON] et al. [20]. In all of the cases in which DOT was measured (measurements were conducted at the phase in which polyols were accumulated into the medium), and for all of the \(Gly_{0}\) quantities set into the medium, DOT values were between 20% and 50% \(v/v\). Moreover, in several of the shake-flask cultures performed, ammonium ion concentration into the medium was determined with an ammonium selective electrode (SA 720, Orion; USA), according to previously indicated procedure [25]. In all the kinetic experiments both in shake-flask and bioreactor trials, each experimental point presented in the figures and the tables is the mean value of two measurements deriving from two independent experiments (SE in most of the experimental points was \(\leq\)18%).