Results obtained so far on the comparison of several pretreatment
methods for elephant grass showed that the pretreatment
with NaOH is the best because it leads to the highest production
of sugars and ethanol. Therefore, this pretreatment was studied
in more detail to improve the ethanol yield. A Draper–Lin central
composite design, with three central points, was used to optimize
the pretreatment conditions and maximize the ethanol yield.
Experimental conditions are shown in Table 1.