Continuous enzymatic saccharification and its rheology profiling under high solids loading of lignocellulose biomass

Continuous saccharification of lignocellulose biomass is an important process option for industrial biorefinery practice. Continuous saccharification in industrial operations needs to be performed under high solids loading to obtain a high titer of fermentable sugars for the consequent fermentation or the simultaneous saccharification and fermentation (SSF), which also produces highly viscous hydrolysates, two orders of magnitude greater than the regular fermentation medium. The rheological properties in the continuous saccharification should be characterized for bioreactor design. This study investigated the process efficiency of continuous enzymatic saccharification of two typical lignocellulose feedstocks (corn stover and wheat straw) under high-solids loading. The rheological change was profiled under varying saccharification parameters such as dilution rate, solids loading, and enzyme dosage. The apparent viscosity of the high solids loading hydrolysates was found in the range of 0.11–0.56 Pa·s, which allowed the efficient transportation by the regular pump in vessels and pipelines. The presence of inhibitors generated from dry acid pretreatment showed a negligible effect on the hydrolysis efficiency of the continuous saccharification and provided an environment away from microbial contaminations in the hydrolysates. The study provided important technical support for the process and reactor designs of continuous saccharification of lignocellulose feedstock under high solids loading.