Discipline: Chemistry and Chemical Sciences
Subcategory: Materials Science
Room: Exhibit Hall A
Rachel Hannah - University of Arkansas at Pine Bluff
Co-Author(s): Tuhua Zhong, Washington State University, Pullman, Washington; Michael P. Wolcott, Washington State University, Pullman Washington
Lignocellulosic biomass can be converted to bio-ethanol by enzymatic hydrolysis of cellulose in lignocellulosic biomass followed by the fermentation of the resulting sugars. The recalcitrance of cellulose due to its crystalline structure and the surrounding lignin and hemicellulose prevent the enzymes accessing to celluloses, thus resulting in lower enzymatic digestibility, low sugar yield, and the high cost of the hydrolysis process. Mechanical milling usually demands high-energy inputs, which is a major barrier to its commercialized application. The objective of this study here is to investigate the effects of catalyst sodium hydroxide (NaOH) used in the pilot-scale milling on physicochemical properties of amorphized particles and sugar yield, to assess the mechanochemical- assisted pretreatment energy efficiency associated with the sugar recovery. The catalyst NaOH was expected to speed up the deconstruction of the lignin-carbohydrate complexes and crystalline structure in lignocellulosic biomass when in combination with the mechanical pulverization/amorphization forces generated by a Spring Suspended Vibratory Tube Mill (SSVTM). We conducted particle size, bulk density, and crystallinity analysis to measure the difference the catalyst NaOH made in the physicochemical of the resulting amorphized wood particles. So far, the results indicated that at the same milling time, the particle size of wood particles milled with catalyst is slightly smaller than that of those milled without catalyst. We also found that particles milled for 20 minutes without catalyst are slightly denser that those milled with the catalyst. On the other hand, particles milled for 45 minutes with the catalyst are denser than particles milled without the catalyst. Finally, we carried out enzymatic hydrolysis and carbohydrate composition determination and enzymatic hydrolysis sugar yield analysis. We used enzymes Cellic CTec2 and HTec2 (Novozymes) during enzymatic hydrolysis as a pretreatment to further digest the lignocellulose structure. This makes it easier to collect a more considerable amount of undamaged cellulose sugar that can be used in the bioethanol production for bio-jet fuels. The results confirmed that samples milled with catalyst produced higher sugar yield than those milled without catalyst. Although this is the answer we seeked, the data was much lower than expected. We concluded that this was because pH levels in the samples were too high for enzymatic activity. Attempting to solve, we added citric acid to adjust pH levels to optimal pH (4.8). Sugar yields were much higher after this addition, but still not as high as expected. We then concluded that enzymes that were being used were bought over five years ago and may be denatured. In the future, new enzymes will be purchased, and samples will be tested for higher sugar yields.
Funder Acknowledgement(s): This work was supported by the National Institute of Food and Agriculture (NIFA), USDA Award Number: 2017-67032-26005.
Faculty Advisor: Michael P. Wolcott, email@example.com
Role: I focused on using sodium hydroxide as a catalyst to speed up the deconstruction of lignin in biomass. I performed all methods and ran all test.