Tuesday, May 3, 2011
Compressed-hot water flowthrough (FT) pretreatment has been shown to be effective to increase the digestibility of lignocellulose while reducing the use of chemicals compared with other pretreatment methods. In this study, various hot water flowthrough pretreatments were performed on bagasse, corn stover, pine, poplar and switchgrass to determine their effectiveness on different feedstocks. FT, batch and hot water rinsed batch pretreatments were performed and followed by testing the pretreated substrates using simultaneous saccharification and fermentation (SSF) with various enzyme loadings and C. thermocellum fermentations. For FT, it was found that C. thermocellum fermentation generally gives higher glucan conversions after 96 hours than SSF (10 FPU/g). Conversion was remarkable for C. thermocellum on FT pretreated bagasse and corn stover (above 96%) and was good for switchgrass (90%) and poplar (80%). However, the conversion for pine was much lower (10-30%), probably because of its different lignin structure and higher lignin content after FT pretreatment. For SSF, enzyme loadings below 5 FPU/g glucan gives lower than 60% conversion in 96 hrs even for FT pretreated substrate. Hot water rinsed batch pretreatment resulted in substrates exhibiting much higher solids digestibility than batch pretreatment, suggesting that the recondensation of solubilized compounds could be the cause of reduced performance for batch pretreatment.