(386c) Dilute Alkali Treatment Followed By Mechanical Refining to Enhance Sugar Conversion

Lignocellulosic biomass has acetate groups in xylan backbone, which can be released during pretreatment process and negatively affect the microbial growth during the fermentation process. It has been reported that the deacetylation of biomass with alkaline reagents can remove both acetate groups and partial fraction of lignin, and enhance the carbohydrate conversion yield in a subsequent enzymatic hydrolysis, as well as the efficiency in the downstream fermentation process. Meanwhile, mechanical treatment is recently considered as a promising technology to enhance the yield of carbohydrate conversion in pretreated lignocellulosic biomass. The purpose of this work is to optimize deacetylation process for corn stover with minimum loading of NaOH with a post-treatment of mechanical refining. Due to cost burden of NaOH and its recycling process, the decrease of NaOH loading is critical for economic feasibility of the whole conversion process.  Preliminary data presented that deacetylation at 80 °C for 20 min with 2% NaOH (w/w of biomass) could remove 70.6% of acetate groups in raw corn stover, and at the elevated temperature of 140 °C for the same reaction time and NaOH loading, 74.0% of acetate groups were removed. With less than 4% difference in changes of acetyl content, the resulting in carbohydrate conversion yield showed substantial changes between the two deacetylated biomass, 35.8 and 52.2%, respectively. When they are subjected to mechanical treatment, the conversion yields for both samples were improved to 50.0 and 65.0%, respectively. To mitigate the decline in pretreatment yield from lower NaOH loading, the effect of pretreatment at the elevated temperature and mechanical refining under higher temperature/pressure will be also considered in this study.