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Effects of Enzyme Loading, Densification, and Storage on AFEX-Pretreated Biomass for Ethanol Production

Biersbach, Gwen, Rijal, Binod, Pryor, Scott W., Gibbons, William R.
Applied biochemistry and biotechnology 2015 v.177 no.7 pp. 1530-1540
Panicum virgatum, Spartina pectinata, adverse effects, ammonia, beta-glucosidase, biomass, briquettes, bulk density, corn stover, endo-1,4-beta-glucanase, ethanol, ethanol production, feedstocks, fermentation, glucans, hydrolysis, saccharification
Corn stover, switchgrass, and prairie cordgrass were treated with an ammonia fiber expansion (AFEX) process and a novel densification method (ComPAKco). Separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) were used to evaluate impacts of densification. ComPAKco densification is characterized by low-temperature and low-energy requirements, resulting in compacted biomass briquettes (CBB) 1–2 cm square, with a bulk density of 380–460 kg/m³. Feedstocks were evaluated before and following AFEX pretreatment, after densification, and after storage. Two enzyme doses were tested. The low rate used 5 filter paper units (FPU) of Spezyme CP (cellulase) and 21.3 cellobiase units (CBU) of Novozyme 188 (aka NS50010 [β-glucosidase]) per gram of glucan. The high dosage rate was three times higher and resulted in 40–56 % and 33–82 % higher ethanol yields with SHF and SSF, respectively. Trials revealed no adverse effect on ethanol yield following densification or 6-month storage of densified, AFEX-pretreated feedstocks.