Biomass Fundamentals
Module 14: Lignin II:
Specialty Applications
A capstone course for
BioSUCCEED:
Bioproducts Sustainability: a University Cooperative
Center of Excellence in EDucation
The USDA Higher Education Challenge Grants program gratefully
acknowledged for support
This course would not be possible without
support from:
USDA
Higher Education Challenge (HEC) Grants Program
www.csrees.usda.gov/funding/rfas/hep_challenge.html
What is “lignin?”
• The amorphous glue that
binds carbohydrate bundles
• A complex, polydisperse
(weight average
MW/Number average MW
 measure of distribution of
individual MWs) polymer
• A source of endless
discussion for the exact
nature of its biosynthesis in
plants (enzyme controlled vs.
random radical coupling)
• C9 polypropylphenol
derivative
O
CH2OH
CHOH
OH 3C
O
CH2OH
O
CHOH
CH2OH
CHOH
OH 3C
O
O
OH
OH 3C
CH2OH
O
O
O
O
OH 3C
OCH3
O
O
OH C
OCH33
HO
CH2OH
O
CH2OH
OCH3
OH 3C
CHOHCH OH
2
CHOH
O
CH2OH
OH
CHOH
O
O
O
CH2OH
CH2OH
CHOH
CHOH
O
O
O
O
CHOH
OH 3C
OH 3C
OCH3
CH2OH
OCH3
O
CH2OH
CHOH
H2COH
O
OCHH3 2COH
O
OH 3C
O H3CO
CHOH
O
OH 3C
O
CH2OH CH2OH
OCH3
O
CHOH
O
O
OH
OCH3
OH 3C
OCH3
OH
O
CHOH
OCH3CH2OH
O
OH 3C
CHOH
OCH3
CH2OH
OH
CH2OH
O
CHOH
CH2OH
OH
Lignin Biosynthesis
Structures of Lignin Precursors
Flavonoids: Chemical Offshoots of
Lignin Biosynthesis
• 15 carbon atom compounds (C6C3-C6) – over 4000!
• Polyphenol
• Phytochemicals (phenolic acids,
stilbenes, polyphenols)
• Antioxidants
• CV health: reduce agglomeration
of platelets in endothelia
• Assist lignification of cell walls in
plants in response to injury
• Antimicrobials
Biologically Active Isoflavonoid
• Rotenone comes from
Derris root and
Lonchocarpus species
• Insecticide
• Fish poison
• Topical treatment of
head lice, scabies, and
ectoparasites
Rheological Properties of Lignin
• Schematic illustration of
secondary cell wall of spruce
tracheids
• Between ordered cellulose fibrils
is the lignin-hemicellulose matrix
• Various vibrational studies (static
& dynamic FT-IR) of lignin
functional groups suggest lignin is
ordered in plane with the plane of
cell wall surface
• Distribution, however, is not
ISOTROPIC in fiber wall
Rheological Properties of Lignin,
Part Deux
• Monolignols couple/polymerize under environmental
constraints along fiber axis to ordered polysaccharide matrix
• Polysaccharides templates*?
• A high response in a 90° out-of-phase spectrum with lignin
peaks indicates a more viscoelastic behavior for lignin over
carbohydrates – also can move freely in matrix unperturbed
by carbohydrates
*
Lignin in Composite/Industrial
Applications
•
•
•
•
•
Lignosulfonates
Extrusion moldings
Fuel
Fertilizer/agricultural adjuvant
Potential raw material for fine chemical
production
Lignin as a Medical “Tissue”
• Wood and bone possess unique structural
motifs that fulfill requirements of support &
transport of nutrients
• Is it possible, therefore, to use wood as a
implantable material?
• Can it be used, for example, as a femoral
replacement?
Technical Hurdles to Address
•
•
•
•
•
Toxicity
Compatibility
Adsorption
Functionality
Mechanical Properties
What is Bone?
• Ceramic-polymer composite
• Calcium phosphate (hydroxyapatite) and collagen
• The apatite has different metal ions that adjust
solubility and availability of mineral elements to
rest of body
• Small apatite platelets crystallize in preferred
locations on collagen
Ultrastructure of Bone
Attempts to Mimic Bone
• MOE: *Hydroxyapatite + polyethylene – middle ear
implants, maxillofacial reconstruction, & bone repair;
possesses MOE similar to bone
• Porosity: Porites (coral species) have similar pore size &
interconnectivity; CaCO3 (aragonite in coral) 
hydroxyapatite by hydrothermal process
• Hierarchical Structure: tendon, muscle, WOOD, and bamboo
*
van Leeuwenhoek’s Famous
Comment
When he first recognized the Haversian canals in bone in 1693, he
made reference to other hierarchical structures:
Structure & Function of Wood
• Wood is a polymer of 20-30%
lignin and the virtual remainder
carbohydrates
• Tracheid (osteocyte in bone) is
“cell”
• Tracheids consists of 5-30 nm
wide microfibrillar elements
composes of cellulosic strands
(2.5 nm diameter)
• Wood is porous and operates on
negative pressure osmotic
gradients in lumens and valves in
pits – transport in bone is positive
pressure from circulation of
nutrients
Morphological Structure of
Juniperus communis
A: annual rings; B: rays & pits; C: pirs in a ray connecting adjacent tra
Helical texture of spiraling cellulose strands outside a tracheid
Bone & Wood
• Collagen is bone’s counterpart to wood’s
cellulose
• Alternating fibrillar orientation in the
various lamellae in bone and wood imparts
strength & toughness
• Pore networks differ only in size and
connectivity
Material Property Chart for
Orthopedics
Histological Section of Juniper
Wood
A: cortical bone after 3 mos.
B: cortical bone after 6 mos.
C: trabecular bone after 6
mos.
Conclusions from Medical Study
• No infection, serendipitously due to wood oils
• Boiling wood to remove excess oil and any
microorganisms lowered MOE, better mechanical
fit to wood (see chart)
• Wood well tolerated by body – surrounded by
bone
• Even bone growth into open pores and artificial
microchannels (a priori machining) for improved
integration