Fermentation of Lignocellulose by Thermophilic Bacteria at High Solids Concentration: Diagnostic Experiments Aimed at Identifying Factors that Diminish Performance at High Solids

• Grant number: 22/00359-8
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Effective date (Start): April 01, 2022
• Effective date (End): March 31, 2025
• Field of knowledge: Engineering - Chemical Engineering
• Principal Investigator: Lee Howard Lynd
• Grantee: Carla Ferreira dos Santos Vieira
• Host Institution: Centro de Biologia Molecular e Engenharia Genética (CBMEG). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil
• Associated research grant: 18/25682-0 - Advanced second generation biofuels laboratory, AP.BIOEN.SPEC

Abstract

In order to be economically feasible, current and envisioned 2G biofuel production processess feature solids loading between about 15 to 20 wt.% on a dry basis, corresponding to ethanol titers of 5 to 7 wt.% (Lynd et al., 2002). The upper end of this range is constrained by the high viscosity of unreacted lignocellulose slurries, and associated solids delivery and mixing challenges. The lower end of this range is constrained by low ethanol titers, which increase the cost of both fermentation and distillation. Operating C-CBP at such high solids loadings entails both engineering and biological challenges. Continuously-fed bioreactors will be used in order to operate at solids loadings higher than can be accommodated by operating in batch mode (limited to < 100 g/L). C. thermocellum does not ferment pentose sugars, although its cellulase system readily solubilizes hemicellulose (Paye et al., 2016). Thus monococultures of C. thermocellum growing on lignocellulose accumulate soluble hemicellulose hydrolysis products, which are known to inhibit cellulase activity (Verbeke and Elkins, 2017). Defined cocultures of C. thermocellum and a hemicellulose-fermenting microbe such as T. thermosaccharolyticum will be investigated as a means to alleviate this problem, using improved strains developed by the Biotechnology Focus area as available. Strains subjected to extended cultivation and hence evolution will be evaluated in the Laboratory Adaptive Evoltution project within the A2G lab.