Mechanical milling and membrane separation for increased ethanol production during simultaneous saccharification and co-fermentation of rice straw by xylose-fermenting Saccharomyces cerevisiae
Sasaki, K.; Tsuge, Y.; Sasaki, D.; Teramura, H.; Inokuma, K.; Hasunuma, T.; Ogino, C.; Kondo, A.
Bioresource Technology 185: 263-268
ISSN/ISBN: 1873-2976 PMID: 25776893 DOI: 10.1016/j.biortech.2015.02.117
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±3.4gL(-1) and 45.3±4.4gL(-1) of ethanol production after 48h by xylose-fermenting Saccharomyces cerevisiae from solid fractions (200 and 250gL(-1)) of pretreated rice straw with 5 filter paper unitg-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 250gL(-1) solid fraction increased ethanol production to 52.0±0.4gL(-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.