Ethanol production from hydrothermal pretreated corn stover with a loop reactor

Hydrothermal pretreatment on raw corn stover (RCS) with a loop reactor was investigated at 195 °C for different times varying between 10 min and 30 min. After pretreatment, the slurry was separated into water-insoluble solid (WIS) and liquid phase. Glucan and xylan were found in the both phases. The pretreatment condition showed a significant impact on xylan recovery.

As the pretreatment time prolonged from 10 min to 30 min, the xylan recovery from liquid phase changed between 39.5% and 45.6% and the total xylan recoveries decreased from 84.7% to 61.6%. While the glucan recovery seemed not sensitive to the different pretreatment times. The glucan recovered from liquid was from 4.9% to 5.6% and the total glucan recoveries from all the pretreatments were higher than 98%.

Besides HMF and furfural, acetic, lactic, formic and glycolic acids were also found in the liquid phase. All the concentrations of these potential inhibitors were lower enough not to affect the activity of the Saccharomyces cerevisiae (S. cerevisiae). Compared with the ethanol production of 32.4% from the RCS with S. cerevisiae, all the WISs gave higher ethanol productions ranging between 61.2% and 71.2%.

When the xylan was taken into consideration, the best pretreatment condition would be 195 °C, 15 min and the estimated total ethanol production was 201 g kg−1 RCS by assuming the fermentation of both C-6 and C-5 with the ethanol yield of 0.51 g g−1 and 0.47 g g−1, respectively.