Mechanical milling and membrane separation were applied to simultaneous saccharification and co-fermentation from hydrothermally pretreated rice straw. Mechanical milling with minimized 4 cycles enabled 37.5 +/- 3.4 g L-1 and 45.3 +/- 4.4 g L-1 of ethanol production after 48 h by xylose-fermenting Saccharomyces cerevisiae from solid fractions (200 and 250 g L-1) of pretreated rice straw with 5 filter paper unit g-biomass(-1) cellulase (respectively, 77.3 +/- 7.1% and 74.7 +/- 7.3% of theoretical ethanol yield). Use of a membrane-based process including nanofiltration and ultrafiltration increased the sugar concentrations in the liquid fraction of pretreated rice straw and addition of this liquid fraction to 250 g L-1 solid fraction increased ethanol production to 52.0 +/- 0.4 g L-1 (73.8 +/- 0.6% of theoretical ethanol yield). Mechanical milling was effective in increasing enzymatic hydrolysis of the solid fraction and membrane separation steps increased the ethanol titer during co-fermentation, leading to a proposal for combining these processes for ethanol production from whole rice straw. (C) 2015 Elsevier Ltd. All rights reserved.