Cellulosic Biofuels and BioproductsOvercoming Technical Challenges

Tina JeohAssociate Professor

Biological and Agricultural Engineering

January 13, 2016

ADVANCE Scholar Awards Symposium

In the beginning...

Transportation Energy in 2014

Residential22%

Commericial19%

Industrial32%

Transportation27%

Natural Gas3%

Petroleum92%

Electricity<0.1%

Biofuels5%

Total Energy Used in 2014 = 98.32 QBtu

Glucose and other sugars Fermentation Biofuels

Valuable Co-products!

Cellulosic Biomass

Getting the sugars from cellulosic biomass is a major bottleneck.

Cellulose Hydrolysis is still an unsolved puzzle

Why does the reaction slow down long before the reactant/substrate runs out?

Why are not all cellulose hydrolyzed similarly?

Cellulase hydrolysis of Cellulose

E

EE

Time[Sol

uble

Fer

men

tabl

e Su

gars

]Sp = Productive binding sitesEb,p = Productively bound cellulase

[ ] [ ]pbcat Ekdt

Sugarsd,=

𝑆𝑆𝑝𝑝,𝑡𝑡 = 𝑆𝑆𝑝𝑝 + 𝐸𝐸𝑏𝑏,𝑝𝑝

Initial hydrolysis rate is limited by the productive binding capacity of the cellulosic substrate.

The Productive Binding Capacity (Sp,t) of Cellulose Substrates

Cellulose[Sp,t]

(μmole/g)

BC 0.9 ±0.2

Swollen FP 0.4 ± 0.1

FP 0.09 ± 0.01

MCC 0.03 ± 0.01

AC 0.03 ±0.02

Microcrystalline CelluloseFilter Paper

Swollen Filter Paper

Differences in cellulose can be distinguished by their initial productive binding capacity ([Sp,t])

Algal Cellulose

Bacterial Cellulose (BC)

TrCel7A hydrolysis of Bacterial Cellulose

0 10 20 30 40 50

Exte

nt o

f Hyd

roly

sis

(%)

0

20

40

60

80

100

2x2µm

Jeoh, Tina, Santa-Maria, Monica C., & O’Dell, Patrick J. (2013). Assessing cellulose microfibrillar structure changes due to cellulase action. Carbohydrate Polymers, 97(2), 581-586. doi: http://dx.doi.org/10.1016/j.carbpol.2013.05.027

TrCel7A hydrolysis of Algal cellulose

Time (hours)

0 20 40 60 80 100 120

Exte

nt o

f Hyd

roly

sis

(%)

0

20

40

60

80

100 325x500nm

Modeling the depletion of accessible productive binding sites

0.00

0.05

0.10

0.15

0.20

0.25

0.0 4.0 8.0 12.0 16.0 20.0 24.0

[Spt

] (um

oles

/g)

Time (hours)

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

0.0 4.0 8.0 12.0 16.0 20.0 24.0

[Cel

lobi

ose]

(mM

)

Time (hours)

No perturbation of Spt

Linear Decrease in Spt

Exponential Decrease in Spt

Experimental Data

𝑆𝑆𝑝𝑝,𝑡𝑡 = 𝑆𝑆𝑝𝑝 + 𝐸𝐸𝑏𝑏,𝑝𝑝 𝑑𝑑 𝑆𝑆𝑝𝑝,𝑡𝑡

𝑑𝑑𝑡𝑡= 𝑑𝑑 𝑆𝑆𝑝𝑝

𝑑𝑑𝑡𝑡+ 𝑑𝑑 𝐸𝐸𝑏𝑏,𝑝𝑝

𝑑𝑑𝑡𝑡≠ 0

𝑑𝑑 𝑆𝑆𝑝𝑝,𝑡𝑡

𝑑𝑑𝑡𝑡= 𝑑𝑑 𝑆𝑆𝑝𝑝

𝑑𝑑𝑡𝑡+ 𝑑𝑑 𝐸𝐸𝑏𝑏,𝑝𝑝

𝑑𝑑𝑡𝑡= 0

Take aways from my talkSolving the mechanism of cellulose hydrolysis is a critical but unmet challenge towards enabling the Cellulosic Biofuels Industry.

The productive binding capacity of cellulose limits the initial hydrolysis rate.

The evolution of the concentration of accessible productive binding sites limits long term rates and extent of hydrolysis.

Image credit: Vincent Eijsink

STEM for Girls!• Annual event for 10-12 year old (5-6th grade)

girls from Sacramento and Woodland.

• In partnership with• Women in Science and Engineering (WISE)• Women’s Research and Resources Center

(WRRC)• ISIS Education

• local (Davis) non-profit offering technology education programs for girls.

• Currently funded by NSF

AcknowledgementsGraduate Students

- Maria Cardona (recently graduated)

- Nara Karuna

- Ryan Kawakita

- Akshata Mudinoor

- Jenn Nill

- Scott Strobel

Research Assistants

- Chris Roberts

- Kevin Hudnall

Funding Agencies

- NSF

- USDA

UC Davis Collaborators

- David Block

- Kyria Boundy-Mills

- Mike McCarthy

- Nitin Nitin

- Sanjai Parikh

- Bob Powell

- Chris Simmons

- Heather Lou (WRRC)

External Collaborators

- Peter Goodwin (LANL)

- Mike Crowley (NREL)

- Gregg Beckham (NREL)