Fermentation of lignocellulose by thermophilic bacteria at high solids concentration

• Grant number: 21/11492-8
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate (Direct)
• Start date: March 07, 2022
• End date: March 06, 2023
• Field of knowledge: Engineering - Chemical Engineering
• Principal Investigator: Lee Howard Lynd
• Grantee: Isabela Uematsu Zambello
• Supervisor: Evert Holwerda
• Host Institution: Centro de Biologia Molecular e Engenharia Genética (CBMEG). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil
• Institution abroad: Dartmouth College, United States
• Associated to the scholarship: 21/05398-9 - Fermentation of lignocellulose by thermophilic bacteria at high solids concentration: diagnostic experiments aimed at identifying factors that diminish performance at high solids, BP.DD

Abstract

In Brazil, the main feedstock used for E1G production is sugarcane crop, which results in a large amount of bagasse that can be used for E2G production. The sugarcane bagasse, like all lignocellulosic materials, is known for its recalcitrance. In order to be economically feasible, current and envisioned 2G biofuel production processes feature solids loading between 15 to 20 wt.% on a dry basis, providing ethanol titers of 5 to 7 wt.%. The upper end of this range is constrained by solids handling and mixing challenges. The lower end of this range is constrained by low ethanol titers, which increases 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). Clostridium thermocellum is a cellulolytic and thermophilic anaerobe, able to solubilize lignocellulose being a promising candidate for CBP. Even though its cellulase system readily solubilizes hemicellulose, it does not ferment pentose sugars. Thus, monocultures of C. thermocellum growing on lignocellulose accumulates soluble hemicellulose hydrolysis products, which are suspect to inhibit solubilization. This project aims to document and characterize solubilization performance at increasing solids loading for sugar cane bagasse using C. thermocellum and cocultures of saccharolytic organisms. (AU)