METABOLIC POTENTIAL OF THE DM YEAST (Saccharomyces cerevisiae) TO PRODUCE BIOETHANOL

We studied the metabolic capacity to produce ethanol of DM yeast (S. cerevisiae) using glucose as carbon source. The concentration of residual glucose (DNS method), ethanol (gas chromatography) and biomass (OD 620 nm) were determined. In addition, the kinetic parameters were estimated (μ_max and K_s) of each case using the Monod model. The composition of the culture medium used was (g/L): yeast extract 0.5, KH₂PO₄ 1.0, MgSO₄•7H₂O 0.5 and 2.0 NH₄Cl. Glucose was added at 30 g/L for the inoculum and 200 and 300 g/L in the production medium. The medium were placed in Erlenmeyer flasks, the pH was adjusted to 5.0 and sterilized at 121 °C for 15 minutes. The inoculum media was inoculated using slant with yeast growth, and incubated 16 h at 30 °C, 150 rpm. After this time the content was transferred to this flask corresponding production flask and incubated under the same conditions, but for 120 h. Samples were taken at regular time intervals, and was determined residual glucose, ethanol and biomass. According to these, the metabolic potential of the strain is appropriate for the production of ethanol, since ethanol yields (Y_EtOH/sus) are 70 and 98% of the theoretical maximum yield (0.51) for 200 and 300 g/L respectively. Moreover, the relatively low biomass yield may suggest that reductive catabolism of yeast is being stimulated by a high concentration of glucose.