Environmental Engineering Reference
In-Depth Information
Bioenergy crop
Plant cells
Plant cell wall
Lignin
Hemicellulose
Cellulose
Cellulose
microfibril
Sugar
molecules
Glucose
FIGure 4.1 (see color insert)
Plant wall recalcitrance: A key scientific challenge. (From U.S. DOE,
Bioenergy research centers: An overview of the science, Genome Management Information Systems, Oak
Ridge National Laboratory, 2009.)
in separate microbial fermentations on-site or at commercial enzyme manufacturing plants, typically
utilizing genetically modified fungal hosts (
Trichoderma reesei
,
Aspergillus niger
,
Penicillium
funiculosum
,
Humicola insolens
,
etc.) grown in expensive stainless steel fermenters under aerobic
and aseptic conditions as submerged cultures. Commercial enzyme manufacturers produce these
enzymes during large-scale (up to ~300,000 L) aerobic fermentation, which requires energy for
fermenter and media sterilization, agitation for mixing viscous fungal suspensions, gas compression
for air/oxygen sparging, fluid heating for temperature control, pumps for fluid transfer, etc. This is
followed by downstream processing, which may include host cell deactivation and/or removal, pro-
tein concentration, and stabilization/formulation.
