biomass conversion: opportunities in lignin management · 2016. 12. 6. · biomass conversion:...
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Biomass conversion: opportunities in lignin management
Clint ChappleDepartment of Biochemistry
Purdue University
Targets for biomass improvement
• Yield
• Water and nutrient use efficiency
• Pest and pathogen resistance
• Biomass quality
Targets for biomass improvement
• Yield
• Water and nutrient use efficiency
• Pest and pathogen resistance
• Biomass quality
Lignin is critical for plant survival
• structural support• water transport
• important impact on bioenergy and bioprocessing
• large commitment of fixed carbon
• high energy density
Lignin is a biosynthetically plastic polymer
Bonawitz and Chapple, Ann Rev Genetics, 2010
Lignin is a biosynthetically plastic polymer
OOMe
OMeO OH
O
OH
OMe
O
HO
OMe
OH
OMeO
HO
O
HO
HO
OH
O
OH
OMe
OMe
O
MeO
OH
OMe
HO OH
HO
OH
MeO
• Nucleic acid synthesis• Template-dependent
• Protein synthesis• Template-dependent
• Polysaccharide synthesis• Enzyme specificity-directed
• Lignin synthesis• Random radical coupling dependent on precursor supply
Opportunities for lignin engineering
• Block lignin synthesis
• Change lignin composition
• Redirect lignin monomers
• Alter lignin localization
Mutant screens can identify genes important to processes of interest
Normal plant
↓ mutagenesis
Mutant with trait of interest
↓ gene identification
Understanding of gene function
Lignin is a biosynthetically plastic polymer
Bonawitz and Chapple, Ann Rev Genetics, 2010
Lignin modification-induced dwarfing (LMID)
Schilmiller et al., Plant J. 2009
Lignin is a biosynthetically plastic polymer
Bonawitz and Chapple, Ann Rev Genetics, 2010
Lack of C3'H reduces lignin content andleads to novel lignins
Franke et al., Plant J, 2002
Lignin is a biosynthetically plastic polymer
Bonawitz and Chapple, Ann Rev Genetics, 2010
ref4 and rfr1 are required for lignin regulation
ref4 and rfr1 are required for lignin regulation
REF4 and RFR1 are components of theMediator complex
P Cramer Lab, Gene Center, University of Munich
med5a/bref8-1
med5a/bref8-2
wild type ref8-1med5a/b ref8-2
Disruption of MED5 rescues the dwarf phenotype of ref8
Bonawitz et al., Nature, 2014
ref8-1 mutants show widespread MED5-dependent transcriptional reprogramming
med5a/b89
216med5a/b ref8-1
ref8-14441
95
39
43025
med5a/b19
196med5a/b ref8-1
ref8-13360
54
12
37147
up-regulated down-regulated
(DeSeq, false discovery rate <0.05)
Bonawitz et al., Nature, 2014
med5a/b ref8-1 mutants synthesize predominantly H lignin
syringyl (S)
guaiacyl (G)
p-hydroxyphenyl (H)
wild type med5a/b med5a/b ref8-1
Yuki Tobimatsu, John Ralph, Wisconsin
med5a/b ref8 mutants show facilitated saccharification
0
20
40
60
80
100
0 24 48 72
0
20
40
60
80
100
0 24 48 72
gluc
ose
rele
ase
(%)
wild type
med5a/b
med5a/b ref8-1
time (hrs)
no pretreatment liquid hot water pretreated
Eduardo Ximenes, Mike Ladisch, Purdue
Suppressor screens can identify genes important to processes of interest
Normal plant
↓ mutagenesis
Mutant with trait of interest
↓ mutagenesis
Mutant plant in which trait is abolished
Suppressors of ref4-3 may identify other proteins required for phenylpropanoid regulation
Dolan et al., unpublished
Whole genome sequencing identified intragenic suppressor mutations and Mediator subunit suppressors
Dolan et al., unpublished
REF4 and RFR1 are components of theMediator complex
P Cramer Lab, Gene Center, University of Munich
Maybe lignin isn’t all bad
• Significant proportion of plant biomass
• More highly reduced than sugars and polysaccharides
• Amenable to catalytic degradation and conversion
OOMe
OMeO OH
O
OH
OMe
O
HO
OMe
OH
OMeO
HO
O
HO
HO
OH
O
OH
OMe
OMe
O
MeO
OH
OMe
HO OH
HO
OH
MeO
Maybe lignin isn’t all bad
Parsell et al., Green Chemistry 2015
Maybe lignin isn’t all bad
Shuai et al., Science 2016
Summary
• We are developing an understanding of the catalysts and regulators that provide us with control over lignin
• The study of Arabidopsis has revealed a previously unknown regulatory circuit for lignin biosynthesis that involves Mediator
• The dwarfing seen in some lignin-deficient plants can be suppressed genetically, indicating that it is an active protein-mediated process
• Plants with high H-lignin are viable and could provide novel inputs for the biorefinery
• Catalytic conversion of lignin into fuels may make more efficient use of biomass
Acknowledgements
Purdue and C3Bio
Nick BonawitzWhitney Dolan
Jake StoutCandy Mao
Bryon DonohoePeter Ciesielski
Eduardo XimenesMike Ladisch
Brian DilkesCharles Addo-Quaye
GCEP
Sirius Li
Yuki TobimatsuJohn Ralph
Chris McClellanClaire Halpin
Wout Boerjan