2.4.2. Substrate concentration
The concentration of the different carbon sources in the media(glucose, lactose, fructose and glycerol) was determined by HighPerformance Liquid Chromatography (HPLC) using Waters Chro-matograph (Model 2414) coupled with refractive index detector(at 65◦C) and an Aminex HPX-87H column (Bio-Rad, Hercules,CA, USA). Sulfuric acid (5 mM) in deionized water was used asmobile phase at a flow rate of 0.5 mL min−1and the sample injec-tion volume was 20 L. Sunflower oil consumption was determinedgravimetrically after extraction with hexane [13].