Simultaneous saccharification and cofermentation of dilute-acid pretreatedyellow poplar hardwood to ethanol using xylose-fermenting Zymomonas mobilis

Simultaneous saccharification and cofermentation (SSCF) was carried out at approximately 15% total solids using conditioned dilute-acid pretreated yel low poplar feedstock, an adapted variant of National Renewable Energy Labor atory (NREL) xylose-fermenting Zymomonas mobilis and either commercial or N REL-produced cellulase enzyme preparations. In 7 d, at a cellulase loading of 12 filter paper units per gram cellulose (FPU/g), the integrated system produced more than 3% w/v ethanol and achieved 54% conversion of all potent ially available biomass sugars (total sugars) entering SSCF, A control SSCF employing Sigmacell cellulose and a commercial cellulase at an enzyme load ing of 14 FPU/g achieved 65% conversion of total sugars to ethanol.