A process for energy-efficient high-solids fed-batch enzymatic liquefaction of cellulosic biomass

• Published in: Bioresource technology Vol. 198; pp. 488 - 496
• Main Authors: Cardona, M.J., Tozzi, E.J., Karuna, N., Jeoh, T., Powell, R.L., McCarthy, M.J.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.12.2015
• Subjects: Batch Cell Culture Techniques; Biofuels; Biomass; Biotechnology - instrumentation; Biotechnology - methods; Cellobiose - chemistry; Cellobiose - metabolism; Cellulose - chemistry; Cellulose - metabolism; Enzymatic hydrolysis; Enzymes - chemistry; Enzymes - metabolism; Fed-batch; Glucose - chemistry; Glucose - metabolism; Hydrolysis; Liquefaction; Magnetic resonance imaging; Magnetic Resonance Imaging - instrumentation; Magnetic Resonance Imaging - methods; Rheology; Rheology - instrumentation; Rheology - methods; Fed-batch; Magnetic resonance imaging; Liquefaction; Rheology; Enzymatic hydrolysis
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2015.09.042

•A fed-batch process for liquefaction was designed to enable high solids hydrolysis.•Yield stress was used as a process control variable to optimize biomass additions.•Upper limit of solids loading was ultimately limited by end-product inhibition.•Enzyme addition schemes impact liquefaction rates and efficiency, and conversion. The enzymatic hydrolysis of cellulosic biomass is a key step in the biochemical production of fuels and chemicals. Economically feasible large-scale implementation of the process requires operation at high solids loadings, i.e., biomass concentrations >15% (w/w). At increasing solids loadings, however, biomass forms a high viscosity slurry that becomes increasingly challenging to mix and severely mass transfer limited, which limits further addition of solids. To overcome these limitations, we developed a fed-batch process controlled by the yield stress and its changes during liquefaction of the reaction mixture. The process control relies on an in-line, non-invasive magnetic resonance imaging (MRI) rheometer to monitor real-time evolution of yield stress during liquefaction. Additionally, we demonstrate that timing of enzyme addition relative to biomass addition influences process efficiency, and the upper limit of solids loading is ultimately limited by end-product inhibition as soluble glucose and cellobiose accumulate in the liquid phase.