The treatment and reutilization of paper sludge (PS) is a worldwide issue. In this study, PS without any pretreatment was used for bioethanol production through simultaneous saccharification and fermentation (SSF) using hyper producer of cellulase and thermotolerant yeast. For saccharification of PS cellulose, cellulase activity was improved from 1.28 x 10(7) FPU m(-3) (wild type) up to 1.52 x 10(7) FPU m(-3) by mutation of Acremonium cellulolyticus C-1 and its carboxymethyl cellulase (CMCase) activity increased 5-fold compared to that of the wild type. In the SSF process, using A. cellulolyticus origin cellulase the highest level of ethanol production was 11.80 and 11.34 kg m(-3) from 50 kg m(-3) untreated PS in 250 cm(3) and 2 dm(3) flask scales, respectively. Ethanol yield based on consumed glucose was 80%. This result exhibits a high ethanol production yield from untreated PS, without using a commercial cellulase, nor any pretreatment of PS during SSF process. (C) 2012 Elsevier Ltd. All rights reserved.