Tuesday, May 1, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
Consolidated bioprocessing (CBP) conversion comprises fermentative microorganisms that produce some or all of the needed biomass hydrolytic enzymes, mitigating the cost of added enzymes. It has been shown previously that down regulation of the caffeic acid O-methyltransferase (COMT) gene in switchgrass (Panicum virgatum) reduced lignin content, reduced S/G ratio, increased sugar release, and improved the yeast-based SSF conversion of the modified switchgrass line compared to the wild type switchgrass. As expected, the dilute acid pretreated wild type and modified switchgrass lines yielded superior products on a (g/g) basis in comparison to the less severe hot water pretreated wild type and modified switchgrass lines during yeast-based SSF. Here we evaluate the fermentation conversion of the genetically modified feedstock with the following very active CBP microorganisms Clostridium thermocellum, Thermoanaerobacterium saccharolyticum, Caldicellulosiruptor obsidiansis, and Caldicellulosiruptor bescii. Comparison of the wild type switchgrass to a modified COMT plant line showed that the transgenic switchgrass yielded over 20% greater total fermentation products on a (g/g) substrate basis. However, results also showed the potential impact of inhibitors during bacterial biomass fermentation and also a differential of inhibition for C. thermocellum, C. obsidiansis, and C. bescii.