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Oral Presentation 5-03 Harnessing Natural Biodiversity for Biomass
Conversion Kevin A. Gray, David Blum, Brian Steer, Walt Callen Dan E. Robertson, Geoff Hazlewood and Jay Short Diversa Corporation 4955 Director’s Pl San Diego, CA 92121 In
the natural world, microorganisms that break down plant structural
polysaccharides play a key role in recycling photosynthetically fixed
carbon. Many different types of
microorganisms, both prokaryotic and eukaryotic, are implicated in a process of
carbon recycling that occurs wherever plants grow. A feature common to nearly all such microorganisms is the
capacity to synthesize a repertoire of functionally related enzymes,
principally hydrolases and lyases, that act in concert to break down the
chemically and structurally complex polysaccharides that account for the bulk
of plant biomass. Our current
understanding of this process is based on studies of cellulases and
hemicellulases from bacteria and fungi isolated from their natural environment
and cultured in the laboratory. Significant
effort has been expended on developing enzymatic processes for converting the
structural polysaccharides from plant biomass to their constituent sugars for
subsequent processing into fuels and chemicals. However, there is a continuing
need for an efficient and economically viable process. This suggests that
existing experimental systems may lack an essential component, or alternatively
that the most active enzyme systems in the natural world have not been
identified and harnessed for this process. Diversa has
unrivalled access to natural biodiversity and the ability to discover novel
enzymes of any type, without first cultivating the native host for the enzyme.
We have used this technology successfully to access enzymes from taxonomically
diverse bacteria growing in ecosystems with widely different conditions of
temperature, pH and ionic strength. Such technology could be used to isolate
novel polysaccharide-degrading enzymes from any environment on Earth. Our existing
enzyme library contains many of the enzymes necessary for complete hydrolysis
of plant structural polysaccharides. These include endoglucanases, α- and
β-glucosidases, endomannanases, mannosidases, galactanases,
arabinofuranosidases, arabinanases, phenolic acid esterases and a collection of
more than 140 endoxylanases, many of which are modular in architecture and
contain functional domains that may be of pivotal importance for effective
hydrolysis of hemicellulose.
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