(561d) Understanding the Impact of High Solids Loadings on Deconstruction of Celf Pretreated Poplar By C. Thermocellum consolidated Bioprocessing (CBP)

Co-solvent Enhanced Lignocellulosic Fractionation (CELF) pretreatment of Poplar was employed to produce glucan-enriched solids as a highly reactive substrate for application to consolidated bioprocessing (CBP) by wild type C. thermocellum DSM 1313. Our previous studies showed that deconstruction of CELF-pretreated poplar by C. thermocellum in shake flasks achieved nearly complete solids solubilization in 24-48 hours at glucan loadings of 5-10 g/L. However, because higher product titers would reduce the cost of downstream product recovery, total sugar solubilization was followed over CBP culture time for 50, 75, and 100 g/L of CELF-pretreated poplar solids generated at different pretreatment severities. In a run at 50 g/L solids loadings, 90% carbohydrate solubilization was achieved at lower CELF pretreatment severity while 96% carbohydrate solubilization was reached at higher severities. In order to gain insights into how solids composition, structural properties, and lignin linkages affected CBP performance, pretreated poplar and fermentation residues were both probed with NMR and Stimulated Raman Spectroscopy, and fermentation broths were characterized to determine if metabolite yields changed with solids loadings. This presentation will be report key factors that impacted the rate and extent of solids solubilization from synergistic pairing of CELF pretreatment with C. thermocellum CBP.