1-04: Implications of the Improved Dedicated Feedstock Populus sp

Lignocellulosic feedstocks are one of the primary substrates for producing liquid biofuels and the implications for improved dedicated biomass sources, such as Populus sp., will be discussed. From sample sets of natural variant and transgenic Populus sp., we evaluated the susceptibility to bioconversion using yeast-based fermentation (separate hydrolysis and fermentation (SHF) and/or simultaneous saccharification and fermentation (SSF)) and consolidated bioprocessing (CBP) with Clostridium thermocellum. We examined six variants from a structured pedigree of hybrid Populus trichocarpa with lignin content ranging from 24-31% with two different pretreatment conditions (hot water and dilute acid) and found that the microbial bioconversion of un-pretreated biomass gave a strong negative correlation between fermentation yield and molecular beam mass spectrometry (MBMS) lignin content. Notably, C. thermocellum displayed superior conversion without any addition of hydrolytic enzymes. However, there was no correlation between fermentation yield and MBMS lignin content after either hot water or dilute acid pretreatment. We also examined, with the same microbial bioconversion platforms, 21 Populus sp. variants from two environmentally different common garden field sites that have an interesting mutation that affects the secondary carbon pathway metabolism and leads to reduced lignin content as low as approximately 16% in some variants. Additionally, gas chromatography-mass spectrometry (GCMS) metabolomic analysis was used to examine fermentation broths to elucidate the relative abundance of lignin derived mono-phenolics and/or aromatic compounds.