which were in the orderof 0.81 g of NaOH g−1of biomass (or 3.25% NaOH at 4 wt% TS).This study was based on a complex central composite design inwhich the process variables were the biomass particle size, the liquid to-solid ratio, the NaOH concentration, and both temperature and time used for pretreatment. However, the effect of varyingthe sonication power was not assessed. Also, the fermentation efficiency of the substrate hydrolysates was not given.