Thursday, May 3, 2012: 9:00 AM
Waterbury Ballroom, 2nd fl (Sheraton New Orleans)
Among the major hurdles in converting lignocellulosic feedstocks into fermentable sugars are the costs associated with pretreatment of the substrate and the cost of enzymes that are required to break down the complex carbohydrates found in plant cell walls. To meet the anticipated demand for such enzymes, significant increases in production capacity must be achieved by enzyme manufacturers, which will also incur added capital expenditures. Expressing cell wall degrading enzymes (CWDEs) directly in substrate plant tissues offers an opportunity to address both of the major cost components of producing biofuels from lignocellulosic sources by simultaneously enabling milder, lower-cost pretreatment conditions and by reducing the amount of exogenous enzymes that must be added during saccharification. Agrivida has been able to generate plant material that can be converted more efficiently into fermentable sugars by expressing a number of different CWDEs in maize or switchgrass. However, expressing highly active CWDEs in plants can seriously retard growth of the plant and may even incur infertility. To overcome this, Agrivida has developed a series of intein-modified CWDEs. Inteins are heterologous protein domains that can catalyze their own excision from a host protein. By developing conditionally-responsive inteins, Agrivida has been able to engineer CWDEs that become active post-harvest, for example, only after exposure to pretreatment temperatures that are well above the temperatures that a crop might encounter in the field. Such intein-modified enzymes can accumulate in transgenic plants without the associated impact on growth or fertility while still enabling enzyme performance during hydrolysis of the biomass.