Oxidative submerged lime pretreatment and high-solids saccharification of corn stover
2020
Rughoonundun, Hema | Fu, Zhihong | Mann, Tyler | Wales, Melinda E. | Holtzapple, Mark T.
Economic commercial-scale production of biofuels from lignocellulose depends, in part, on the development of a suitable pretreatment. In pursuit of that goal, this study assesses the repeatability and effectiveness of submerged lime pretreatment (SLP) of two batches of corn stover designated “Field” and “Module.” SLP was performed with 0.15 g Ca(OH)₂ g⁻¹ biomass and 10 g H₂O g⁻¹ biomass at 50 °C for 4 weeks while purging with air. SLP was repeated 14 times and the results of the mass balances, closures, and compositions of raw and SLP corn stover are presented. The glucan content of corn stover prior to pretreatment was determined to be 36.1 ± 0.7% (Module washed), 37.5 ± 0.4% (Field washed), and 32.6 ± 1.4% (Field unwashed). For washed corn stover (Module and Field), the standard deviation and coefficient of variation were <1%, demonstrating that the measurements were repeatable. For unwashed Field corn stover, because of its higher content of water-soluble components, the variability was slightly higher. The mass closures were above 96% with less than 2% standard deviation. The glucan content of SLP corn stover was 44.3 ± 0.8% (Module washed), 41.5 ± 0.5% (Field washed), and 42.9 ± 2.2% (Field unwashed). This study also presents a reliable analytical method for assessing the enzymatic digestibility of high-solids (15%) lignocellulose. Inositol is used as an internal standard to determine the final reactant volume, which is difficult in high-solids saccharification. After SLP, the overall glucan digestibility was ~80% (standard deviation < 4%, coefficient of variation < 5%), supporting the potential of SLP as a reproducible, cost-effective, and scalable pretreatment.
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