Palm pressed fiber (PPF) is a lignocellulosic material that has potential to be cheap substrate for ethanol production. In this study, the enzymatic hydrolysis of alkali pretreated PPF was investigated. It was found that the hydrolysis with cellulase (10 FPU g (1) of PPF) and beta-glucosidase (10 U g (-1) of PPF) gave the higher reducing sugar production than using cellulase alone. In addition, the optimum condition of simultaneous saccharification and fermentation (SSF) with 6 h of prehydrolysis for ethanol production was the PPF concentration of 100 kg m (-3) with the enzyme loading of cellulase 6.0 FPU g (1) of PPF and beta-glucosidase 3.0 U g (1) of PPF at pH of 5.0 and 35 degrees C. The ethanol concentration of 10.4 kg m (3) and ethanol yield of 192 g kg (1) of cellulose was obtained at the optimum condition in 24 h of SSF. Finally, the effect of prehydrolysis of pretreated PPF prior to SSF on the ethanol concentration was examined with batch and fed-batch mode of hydrolysis. It was found that prehydrolysis with the fed-batch mode did not improve ethanol yield. However, the fed-batch mode of prehydrolysis gave the highest ethanol production of 12.1 kg m (-3) at 12 h of SSF process. Also, it was concluded that the advantages of fed-batch of prehydrolysis prior SSF were the less enzyme requirement and the increasing PPF loading for ethanol production. (C) 2012 Elsevier Ltd. All rights reserved.