The pretreatment step of cellulosic ethanol production generates inhibitory compounds that affect the performance of fermenting microorganisms, and subsequently causes reductions in ethanol yield and productivity. Several researches in ethanol production from second generation feedstocks have therefore focused on the detoxification of inhibitors to increase the efficiency of the ethanol production. The adaptation of the microorganisms to inhibitors presented in raw material hydrolysate is one of the biotechnology routes to improve ethanol yield without any detoxification treatments. The purpose of this work was to adapt Saccharomyces cerevisiae SC90 to improve its ability to ferment toxic cassava pulp hydrolysate pretreated with diluted acid (1 N HCI). The initial total sugar of cassava pulp hydrolysate was 49.79 +/- 0.76 g/I The 20, 40, 60, 80, and 100% (v/v) of hydrolysate were prepared from the initial cassava pulp hydrolysate for the adaptation procedure. The total sugar concentration in all the diluted hydrolysate was adjusted to 50 g/l using glucose and supplemented with 1 g/I yeast extract, 2 g/I (NH4)(2)SO4, 0.5 g/I KH2PO4, and 1 g/I MgSO4.7H(2)O and the pH was adjusted to 5.5. The yeast cells were subcultured twice in the same hydrolysate dilution similar numbers of initial cells were transferred to a more concentrated hydrolysate. Adapted yeast cells from 100% (v/v) of hydrolysate supplemented with nutrient sources and non-adapted cells (the control) were investigated. The growth and fermentation potentials were compared. The adapted cells showed an improvement in sugar utilization and cell viability compared with those of the non-adapted cells. Consequently, the ethanol yield of the adapted cells was improved. These results indicated that the adaptation of the yeast cells to overcome the inhibitory effects of the lignocellulosic hydrolysate could improve the productivity and ethanol yield.
