2-18: Tuning dilute acid pretreatment severity to increase both glucan digestibility and C5 sugar yield

Both high glucan digestibility and high C5 sugar yield are important factors to ensure a successful dilute acid pretreatment process. Although a number of studies have been conducted to improve the glucan digestibility, a systematic analysis of the effect of pretreatment severities on both high glucan digestibility and C5 sugar yield is still needed. The general rules derived from this analysis can be a useful guidance for the development and operation of a commercially relevant biomass-to-ethanol process.

In our study, corn stover was pretreated under a wide range of conditions (acid concentration, temperature, time), and the overall glucose and xylose yields from pretreatment and enzymatic hydrolysis were correlated with the pretreatment severities. It was shown that both high glucan digestibility and high xylose yield could be attained from a dilute acid pretreatment of corn stover that was operated in batch mode. The optimal severity was in the range of 1.4-1.6, where >85% of glucan was digestible and >85% xylose yield was obtainable. Nearly 100% of glucan digestibility could also be reached at relatively high severity (>1.9) but at an expense of increased xylose decomposition. Because of the different optimal pretreatment severities for glucan digestibility and xylose yield, a two-stage pretreatment process could be a good strategy to further improve the sugar yields.