A Demonstration of the Consistency of Maize Stover Pretreatment by Soaking in Aqueous Ammonia from Bench to Pilot-Scale
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Soaking in aqueous ammonia (SAA) is a means of pretreating biomass at moderate temperatures and ammonia concentrations (15% w/w). To establish process consistency and scalability, sieved maize stover was pretreated at 50-ml, 300-ml, and 100-l scales. Each scale was carried out through different methods. Sealed reactor tubes were used for 50-ml pretreatment. Fabric dyeing apparatus was used for the 300-ml pretreatment and a commercial Littleford DVT reactor was used for 100-l pretreatment. For each scale, biomass washing and solid-liquid separations were scaled appropriately. Washed pretreated solids were analyzed for composition and recovery of dry biomass and carbohydrates calculated. Nearly 100% of the glucan content was recovered in pretreated solids at all three scales, indicating the viability of SAA pretreatment. Pretreated solids (15% w/w) were hydrolyzed in a 1-l twin Sigma blade mixer using Cellic CTec2 (15 FPU.g-glucan−1) followed by fermentation in shake flasks. Hydrolytic yields ranged 65–70% across scale treatments. In comparison, fermentative yields averaged 95% across scale treatments, indicating saccharification to be a rate-limiting step in effective bioconversion of lignocellulose.
KeywordsPretreatment Soaking in aqueous ammonia Scale-up Lignocellulose Maize stover Sigma mixer Cellulase Hydrolysis
The authors would like to thank the Lab and Engineering staff at NCERC for their invaluable support through the project, and Graduate Assistant Kimia Kajbaf for her assistance.
The study was funded by the Illinois Corn Growers Association (https://www.ilcorn.org/home).
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