Rheology of enzyme liquefied corn stover slurries: The effect of solids concentration on yielding and flow behavior

Abstract

The measurement of yield stress and shear thinning flow behavior of slurries formed from unpretreated corn stover at solids loadings of 100–300 g/L provides a key metric for the ability to move, pump, and mix this lignocellulosic slurry, particularly since corn stover slurries represent a major potential feedstock for biorefineries. This study compared static yield stress values and flow hysteresis of corn stover slurries of 100, 150, 200, 250, and 300 g/L, after these slurries were formed by adding pellets to a cellulase enzyme solution (Celluclast 1.5 L) in a fed‐batch manner. A rotational rheometer was used to quantitate relative yield stress and its dependence on processing history at insoluble solids concentrations of 4%–21% (wt/vol). Key findings confirmed previous observations that yield stress increases with solids loadings and reaches ~3000 Pa at 25% (wt/vol) solids concentration compared to ~200 Pa after enzyme liquefaction. While optimization of slurry forming (i.e., liquefaction) conditions remains to be done, metrics for quantifying liquefaction extent are needed. The method for obtaining comparative metrics is demonstrated here and shows that the yield stress, shear thinning and shear thickening flow behaviors of enzyme liquefied corn stover slurries can be analyzed using a wide‐gap rheometry setup with relative measuring geometries to mimic the conditions that may exist in a mixing vessel of a bioreactor while applying controlled and precise levels of strain.

Effect of biomass liquefaction on glucose and xylose prices predicted by National Renewable Energy Laboratory biochemical sugar model

“…There are three types of liquefaction: the enzyme route (50 °C, 1 atm), the enzyme mimetic route (140-160 °C, 4.7 atm), and the combined route (50-160°C, 1-4.7 atm). 22 The liquefaction process is catalyzed by an enzyme and/or an enzyme mimetic compound that functions as an enzyme. For all liquefaction routes the pH is to be maintained at 4.8 by addition of ammonium hydroxide.…”

“…It is important to note that liquefaction process uses no sulfuric acid. There are three types of liquefaction: the enzyme route (50 °C, 1 atm), the enzyme mimetic route (140–160 °C, 4.7 atm), and the combined route (50–160°C, 1–4.7 atm) 22 . The liquefaction process is catalyzed by an enzyme and/or an enzyme mimetic compound that functions as an enzyme.…”

“… Glucose, corn steep liquor, corn oil, host nutrients and sulfur dioxide are the inputs in the cellulase enzyme production step (Data courtesy: Szeto et al 22 ). …”

“…The process of liquefaction eases the flow of solids in a biorefinery, this improvement in flow properties is a result of reduction in yield stress. In one instance the yield stress of a slurry was found to decrease from 6806 Pa to 53 Pa through a combined liquefaction process as measured based on rheological measurement methodology described by Szeto et al 22,26 (Fig. 1).…”

“…Glucose, corn steep liquor, corn oil, host nutrients and sulfur dioxide are the inputs in the cellulase enzyme production step (Data courtesy: Szeto et al22 ).A Patil et al Modeling and Analysis: Glucose and xylose prices 50 © 2022 The Authors. Biofuels, Bioproducts and Biorefining published by Society of Industrial Chemistry and John Wiley & Sons Ltd. | Biofuels, Bioprod.…”