Transcripción del resumen del autor. This study investigated the potential of three freeze-dried switchgrass germplasms (St6-1, St6-3E, and St6-3F) as whole plants or their stems and leaves for bioethanol production. Whole switchgrass germplasms contained 24.34-30.95% glucan, 14.68-18.58% xylan, and 17.39-19.46% lignin. Switchgrass samples were pretreated with dilute sulfuric acid at concentrations of 0.5, 1.0, or 1.5% (w/v) for 30, 45, or 60 min at 121 °C and 15 psi. Although lignin degradation was limited, over 80% hemicellulose solublization was observed, especially in leaf samples, and the removal could be enhanced by increasing the pretreatment intensity through acid concentration and treatment time adjustment. Within each germplasm, pretreated samples with the least lignin content or greatest percent hemicellulose (xylan and arabinan) solublization were hydrolyzed enzymatically by cellulase at 0, 15, or 30 filter paper units (FPU)/g of dry biomass supplemented with cellobiase. Although the addition of cellulase greatly improved cellulose to glucose conversion, no significant (p = 0.05) differences were observed between activity levels of 15 and 30 FPU/g of dry biomass. Pretreatment significantly (p < 0.05) improved cellulose conversion in samples with the greatest hemicellulose solublization; complete cellulose hydrolysis was observed in some St6-3F samples. Fermentation of hydrolyzates with Saccharomyces cerevisiae (ATCC 24859) resulted in the greatest ethanol yield of 0.083 g of ethanol/g of raw St6-3F switchgrass whole plant, which was 60% of the theoretical yield. Results from this study demonstrated the potential of new switchgrass germplasms as energy crops for bioethanol production through dilute sulfuric acid pretreatment.

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