Tuesday, May 3, 2011
Consolidate bioprocessing (cbp) conversion comprises fermentative microorganisms that produce some or all 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) improves the yeast-based SSF conversion of the modified switchgrass line compared to wild type switchgrass. Here we evaluate the fermentation conversion of genetically modified feedstock such as switchgrass with the very active cbp microorganism Clostridium thermocellum. As expected, dilute acid pretreatment dramatically improves the yield of fermentation products on a substrate basis (g/g). Comparison of the wild type switchgrass to a modified COMT plant line showed pretreated washed solids yielded over 20% greater total fermentation products for the modified line on a g/g basis. Similarly C thermocellum fermentation of washed unpretreated and hot water pretreated switchgrass demonstrated superior product yield with the modified switchgrass. Comparison of C thermocellum conversion of these modified biomass substrates to other cbp microorganisms will be discussed.