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

OMeO OH

• 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 modification-induced dwarfing (LMID)

Schilmiller et al., Plant J. 2009

Lack of C3'H reduces lignin content andleads to novel lignins

Franke et al., Plant J, 2002

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

med5a/b19

196med5a/b ref8-1

ref8-13360

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 24 48 72

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

OMeO OH

Parsell et al., Green Chemistry 2015

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

Sirius Li

Yuki TobimatsuJohn Ralph

Chris McClellanClaire Halpin

Wout Boerjan

Biomass conversion: opportunities in lignin management · 2016. 12. 6. · Biomass conversion:...

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