Non-severe thermochemical hydrolysis of stover from white corn and sequential enzymatic saccharification and fermentation to ethanol

Abstract

A parametric study, with an initial load of 15%w/w of dry stover from white corn, was conducted to evaluate the sequential thermochemical hydrolysis (TH), enzymatic saccharification (ES) and fermentation of the whole slurry with ethanologenic Escherichia coli. The TH was designed to release the maximum amount of xylose with a concomitant formation of minimal amounts of furans. It was found that 29.0% or 93.2% of the xylan was recovered as free xylose at 130°C after 8 min in the presence of 1% or 2%w/w H2SO4 and produced only 0.06 or 0.44 g/L of total furans, respectively. After 24h of ES, 76.14-77.18 g/L of monosaccharides (pentoses and hexoses) were obtained. These slurries, which contained 0.03-0.26 g/L of total furans and 5.14-5.91 g/L of acetate, were fermented with 3.7 g/L of ethanologenic E. coli to produce 24.5-23.5 g/L of ethanol.

Keywords: Diluted acid pretreatment; Ethanol; Ethanologenic Escherichia coli; Sequential hydrolysis and fermentation; Stover from white corn.