Measurement of Endo and Exo-Glucanase Activities in Cellulase

Using Non-Crystalline Cellulose

Rajesh Gupta and Y. Y. LeeRajesh Gupta and Y. Y. Lee

Department of Chemical EngineeringDepartment of Chemical Engineering

Auburn University, AL 36849Auburn University, AL 36849

yylee@eng.auburn.eduyylee@eng.auburn.edu

AIChE Annual Meeting, San Francisco, CAAIChE Annual Meeting, San Francisco, CA

November 16, 2006November 16, 2006

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OutlineOutline

Overview on Cellulosic EthanolOverview on Cellulosic Ethanol Significance of Cellulase EnzymesSignificance of Cellulase Enzymes Cellulase Action and ActivitiesCellulase Action and Activities

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BIOFUELBIOFUEL

““Sustainable transportation fuel made from Sustainable transportation fuel made from renewable feedstock”renewable feedstock”

Ethanol (E-10, E-85)Ethanol (E-10, E-85) BiodieselBiodiesel Biocrude Biocrude MethaneMethane HydrogenHydrogen

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Biofuels present opportunities for new Biofuels present opportunities for new industry and improved farm economy.industry and improved farm economy.

The fuel ethanol industry alone adds more The fuel ethanol industry alone adds more than $20 billion/year to the US economy.than $20 billion/year to the US economy.

Why Why BiofuelsBiofuels??

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EthanolEthanol BoomBoom

US produced 3.9 billion gallons of BioethaUS produced 3.9 billion gallons of Bioethanol in 2005 (about 3% of US gasoline consnol in 2005 (about 3% of US gasoline consumption) exclusively from corn. umption) exclusively from corn.

94 ethanol refineries nationwide (over 4 bil94 ethanol refineries nationwide (over 4 billion gallons/year capacity).lion gallons/year capacity).

30 new plants and 9 expansions are curre30 new plants and 9 expansions are currently under way(=additional 1.8 billion gallontly under way(=additional 1.8 billion gallons/year capacity). ns/year capacity).

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Economic Impact of Corn Based Economic Impact of Corn Based EthanolEthanol

Goals of Renewable Fuel Standard (2005):Goals of Renewable Fuel Standard (2005):

8 billion gallons by 2012.8 billion gallons by 2012. Ethanol industry will spend $70 billion over 2005-Ethanol industry will spend $70 billion over 2005-

2012.2012. Direct spending and indirect impact will add $200 Direct spending and indirect impact will add $200

billion to GDP over 2005-2012.billion to GDP over 2005-2012. Reduce trade deficit by $64 billion.Reduce trade deficit by $64 billion.

Long term goal: 20 billon gallons by 2020. Long term goal: 20 billon gallons by 2020.

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Constraints of Corn-Based Constraints of Corn-Based EthanolEthanol

Upper limit? Upper limit?

8 billion gallons/year represents 1/3 of total 8 billion gallons/year represents 1/3 of total corn production.corn production.

Marketability of byproducts (DDG).Marketability of byproducts (DDG).

Feedstock other than corn must be Feedstock other than corn must be utilized.utilized.

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Inherent Engineering DifficultiesInherent Engineering Difficultiesin Cellulosic Ethanol in Cellulosic Ethanol

Heterogeneous FeedstockHeterogeneous Feedstock Solid HandlingSolid Handling Slow ReactionSlow Reaction Non-reusable Catalyst (Enzyme) Non-reusable Catalyst (Enzyme)

Cellulose & Cellulose & CellulaseCellulase

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Cellulose Hydrolysis as a Rate ProcessNon-Reaction

ResistancesReaction

Resistances

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CellulaseCellulase Endo-Glucanase Endo-Glucanase

Cellulose Cellulose →→ Scarred Cellulose Scarred Cellulose

Exo-Glucanase (CBH)Exo-Glucanase (CBH)

Scarred Cellulose Scarred Cellulose →→ Cellobiose Cellobiose

ββ-Glucosidase -Glucosidase

Cellobiose Cellobiose →→ Glucose Glucose (Courtesy of(Courtesy of NREL NREL))

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Cellulase Activity DeterminationCellulase Activity Determination

FPU Method (Goshe, 1987)FPU Method (Goshe, 1987)

Uses filter paper (Whatman No.1) as the standard Uses filter paper (Whatman No.1) as the standard substrate. substrate.

Initial rate is measured by one data-point. Initial rate is measured by one data-point.

Released sugars are measured in terms of reducing ends Released sugars are measured in terms of reducing ends by DNS reagent (does not distinguish G1 and G2). by DNS reagent (does not distinguish G1 and G2).

Repeatability is poor because of several factors in Repeatability is poor because of several factors in the procedure that are error-prone.the procedure that are error-prone.

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HPLC for measurement of released sugarHPLC for measurement of released sugar G1 & G2 are converted to glucan for G1 & G2 are converted to glucan for

conversion calculation. conversion calculation. Slope-method (multiple points) for initial rateSlope-method (multiple points) for initial rate

Proposed ModificationProposed Modification

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Activity Determination by initial slope method

Substrate: Filter Paper

Enzyme Loading: 0.01ml/g glucan

y = 0.0128x + 0.0002

y = 0.0114x + 0.0009

y = 0.0168x + 0.0008

0.00%

0.20%

0.40%

0.60%

0.80%

1.00%

1.20%

1.40%

1.60%

1.80%

2.00%

0 0.2 0.4 0.6 0.8 1 1.2

Time(hrs)

%G

luca

n Spezyme CP A

Spezyme Cp B

GC 220

Enzyme Loading: 0.005ml/g glucan

y = 0.007x + 0.0005

y = 0.005x + 0.0016

y = 0.0092x + 0.0013

0.00%

0.20%

0.40%

0.60%

0.80%

1.00%

1.20%

0 0.2 0.4 0.6 0.8 1 1.2

Time(hrs)

%G

luca

n Spezyme CP A

Spezyme Cp B

GC 220

Enzyme Loading (ml/g glucan)

Spezyme CP A Spezyme CP B GC 220

0.01 1.00 0.89 1.31

0.005 1.00 0.71 1.31

Average 1.00 0.89 1.31

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Beyond the FPU?Beyond the FPU?

Observation of G1 & G2 is not sufficient to Observation of G1 & G2 is not sufficient to characterize the cellulase.characterize the cellulase.

Different combination of the three cellulase Different combination of the three cellulase

components may give same FPU.components may give same FPU. Use of substrates with different properties Use of substrates with different properties

may provide additional information.may provide additional information.

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Additional SubstratesAdditional Substrates

Non-Crystalline Cellulose (NCC)Non-Crystalline Cellulose (NCC)

Cello-oligosaccharidesCello-oligosaccharides

Non-Crystalline CelluloseNon-Crystalline Cellulose (NCC)(NCC)

• Amorphous cellulose made in our laboratory Amorphous cellulose made in our laboratory

from crystalline cellulose.from crystalline cellulose.• Hydrogen-bonds in cellulose are disrupted.Hydrogen-bonds in cellulose are disrupted.• Crystallinity is essentially removed.Crystallinity is essentially removed.

αα-Cellulose NCC-Cellulose NCC (Freeze-Dried) (Freeze-Dried)

SEMSEM

(1000X)(1000X)

(3000X)(3000X)

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Cotton NCC

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X-Ray Diffraction Patterns of MicroCrystalline Cellulose),X-Ray Diffraction Patterns of MicroCrystalline Cellulose),a-Cellulose & Non-Crystalline Cellulose a-Cellulose & Non-Crystalline Cellulose

20 25 30 35 40 45 50

2

Inte

nsi

ty

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DSC curves for a–Cellulose [----- ] & NCC [ - - - ] DSC curves for a–Cellulose [----- ] & NCC [ - - - ] Melting Pt. : NCC= 260 oC, a-Cellulose = 340 oCMelting Pt. : NCC= 260 oC, a-Cellulose = 340 oC

-6

-4

-2

0

2

4

Hea

t Flo

w (

W/g

)

0 50 100 150 200 250 300 350 400

Temperature (°C)

––––––– HH_cell1a.001– – – – HH_cell2.002

Exo Up Universal V3.1E TA Instruments

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FTIR graph for Treated & Untreated a-CelluloseFTIR graph for Treated & Untreated a-Cellulose-- A (Untreated a-cellulose), 1.019 (Without baseline -- A (Untreated a-cellulose), 1.019 (Without baseline

correction)correction)----- B (Treated a-cellulose), 2.165 (Baseline ----- B (Treated a-cellulose), 2.165 (Baseline

correction from 1800 cm-1 to 847.27 cm-1correction from 1800 cm-1 to 847.27 cm-1) )

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NCC as a Substrate for Activity Measurement

Highly amorphous ( suitable for Endo-G activity measurement)Highly amorphous ( suitable for Endo-G activity measurement)

Low DP ( suitable for Exo-G activity measurement)Low DP ( suitable for Exo-G activity measurement)

Higher surface area than crystalline celluloseHigher surface area than crystalline cellulose

Extremely high initial hydrolysis rate (short reaction time)Extremely high initial hydrolysis rate (short reaction time)

Endo and Exo-G activities can be measured simultaneously in Endo and Exo-G activities can be measured simultaneously in one experiment.one experiment.

Both activities can be measured using single substrate.Both activities can be measured using single substrate.

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NCC HydrolysateNCC HydrolysateLoading: 0.01 ml Sp CP-A/ g-Glucan, 1 hr

Ce

llo-

olig

os

ac

ch

arid

es

Ce

llob

ios

e

Glu

co

se

Glu

co

se

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Initial sugar releaseInitial sugar release from different substratesfrom different substrates

Enzyme loading: 0.112 ml Sp CP-A/g-glucan,Enzyme loading: 0.112 ml Sp CP-A/g-glucan,15 min.15 min.

Substrate Cellobiose Glucose OligomersCellobiose+

GlucoseTotal

% % % % %Avicel 3.77 1.08 0 4.85 4.85Filter Paper 1.85 0.63 0 2.48 2.48NCC 12.48 9.36 7.52 21.84 29.36

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Schematic Representation of Structural Differences Schematic Representation of Structural Differences between Crystalline Cellulose & NCCbetween Crystalline Cellulose & NCC

Amorphous domain (Substrate for Endo-glucanase)

Reducing Ends(Susbtrate for Exo-glucanase)

Amorphous domain(Substrate for Endo-glucanase)

Reducing Ends(Susbtrate for Exo-glucanase)

E + S Pk

dP= k[E][S]

dt

E Pk’ = k[S]

dP= K’[E]

dt

Crystalline Cellulose NCC

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SOLIDLIQUID

Low DP NCC

COS

CELLOBIOSE

GLUCOSE

Β-G

NCC

Hydrolysis of NCC

Exo-G

Endo-G

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0.5ml 2% sonicated NCC Solution with Buffer0.5ml of diluted Enzyme Solution

Stop the reaction by boiling it for 5min. &

Dilute it 3 times by cold DI water

Stir the content and take two 0.5ml sample containing

uniform mixture liquid and solid

Take liquid samplefor finding the sugar concentration

(From HPLC)

Find the Glucose and Cellobioseconcentration

Incubate at 50oCfor 30min.

Add 3ml DNS reagent in one sample as it is and centrifuge other sample & then add 3ml of DNS in liquid part only. Boil both the sample for exact 5min and cool

the content Immediately. Centrifuge both the sample again and find the absorbance of both

( Solid+Liquid part and only Liquid part )

Measurement of Endo-Glucanase and Exo-Glucanase Activities from NCC

0.5ml 2% sonicated NCC Solution with Buffer0.5ml of diluted Enzyme Solution

Stop the reaction by boiling it for 5min. &

Dilute it 3 times by cold DI water

Stir the content and take two 0.5ml sample containing

uniform mixture liquid and solid

Take liquid samplefor HPLC

sugar analysis

Determine Glucose and Cellobioseconcentration

Incubate at 50oCfor 30min.

Add 3ml DNS reagent in one sample and centrifuge other sample & then add 3ml of DNS in liquid

part only. Boil both the sample for 5min and cool Immediately afterward. Centrifuge the sample

and find the absorbance of the Solid+Liquid part and the Liquid part.

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Activity Determination

Sample calculation

* HPLC results represent mg of sugars generated from the reaction.

Dilution (ml/ml) 0.001 0.0002 0.0001 0 0.001 0.0002 0.0001 0 0.001 0.0002 0.0001 0

(ml/g of substrate) 0.05 0.01 0.005 0 0.05 0.01 0.005 0 0.05 0.01 0.005 0

L 1.123 0.398 0.192 0.016 1.196 0.475 0.295 0.016 1.704 0.662 0.418 0.016

S+L 1.366 0.637 0.399 0.168 1.491 0.721 0.547 0.168 1.994 0.914 0.646 0.168

S 0.243 0.238 0.207 0.152 0.295 0.246 0.200 0.152 0.290 0.252 0.228 0.152

G1 1.032 0.207 0.097 0.000 1.085 0.252 0.109 0.000 0.969 0.431 0.205 0.000

G2 2.268 0.897 0.457 0.000 2.482 1.044 0.415 0.000 1.543 1.436 0.891 0.000

Total Glucan (G1+G2) 3.083 1.039 0.522 0.000 3.335 1.219 0.492 0.000 2.338 1.751 1.031 0.000

Spezyme CP-A Spezyme CP-B GC 220

Enzyme loading

Absorbance

HPLC results

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Absorbance Corresponding to solid part

0.0000

0.0500

0.1000

0.1500

0.2000

0.2500

0.0000E+00

1.0000E-05 2.0000E-05 3.0000E-05 4.0000E-05 5.0000E-05 6.0000E-05

Enzyme Loading

Ab

so

rba

nc

e

Spezyme CP-A

Spezyme CP-B

GC 220

Exo & Endo-G Activity Determinationfrom NCC

Glucose + Cellobiose

y = 7756.4x + 0.0116

y = 4222.6x + 0.0105

y = 4210.1x + 0.0091

0.0

0.1

0.1

0.2

0.2

0.3

0.3

0.4

0.4

0.5

0.0000E+00

1.0000E-05

2.0000E-05

3.0000E-05

4.0000E-05

5.0000E-05

6.0000E-05

Enzyme Loading (ml/ml)

mg

Glu

ca

n E

qu

iva

len

t(G

1+

G2

)

Spezyme CP A

Spezme CP B

GC 220

Run 2: Low enzyme Loading (<0.1 FPU/g-glucan)

Slope RASpezyme CP A 870.00 1.00Spezyme CP B 730.00 0.84

GC 220 1324.00 1.52

Reltive Activity (RA)of Endo-Glucanase

Slope RASpezyme CP A 4210.1 1.000Spezyme CP B 4222.6 1.003

GC 220 7756.4 1.842

Reltive Activity (RA)of Exo-Glucanase

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Summary of Activity Test

Relative Activities Based on Volume

OverallOverall Endo-GEndo-G Exo-GExo-G β-Gβ-G

SubstrateSubstrate Filter PaperFilter Paper CMCCMC NCCNCC AvicelAvicel NCCNCC CellobioseCellobiose

MethodMethod AA BB AA BB AA BB AA

Spezyme CP-ASpezyme CP-A 1.01.0 1.01.0 1.01.0 1.01.0 1.01.0 1.01.0 1.01.0

Spezyme CP-BSpezyme CP-B 0.980.98 0.890.89 1.071.07 0.860.86 1.121.12 1.081.08 0.600.60

GC-220GC-220 1.651.65 1.311.31 1.511.51 1.461.46 1.421.42 1.771.77 2.312.31

A: ConventionalB: Proposed in this work

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Acid Hydrolysis of Acid Hydrolysis of Cello-oligosaccharidesCello-oligosaccharides

Cello-oligosaccharides

Ce

llob

iose

Glu

cose

Glu

cose

4% H2SO4, 121C, 1 hr

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Enzymatic Hydrolysis Enzymatic Hydrolysis of Cello-oligosaccharidesof Cello-oligosaccharides

Cello-oligosaccharides

Cellobios

e

Glucos

e

Cellobios

e

Glu

cose

Cello-oligosaccharides

Enzymatic Hydrolysis15FPU/g-glucan

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Hydrolysis of cello-oligosaccharide by Hydrolysis of cello-oligosaccharide by ββ-glucosidase (-glucosidase (Novo-188Novo-188))

Hydrolysis of Cello-oligosaccharides

0%

5%

10%

15%

20%

25%

30%

35%

0 20 40 60 80 100 120

Time (Hours)

% G

luc

an E

qu

iva

len

t)

Glucose (15 FPU+30 CBU)

Cellobiose (15 FPU+30 CBU)

Glucose (30 CBU)

Cellobiose (30 CBU)

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Hydrolysis of NCC and Cellobiose with Hydrolysis of NCC and Cellobiose with ββ-glucosidase-glucosidase

(Enzyme loading: 7 CBU/ g glucan)(Enzyme loading: 7 CBU/ g glucan)

Release of Glucose in NCC and Cellobiose

0%

4%

8%

12%

16%

20%

0 0.2 0.4 0.6 0.8 1

Time (Hours)

%G

luc

an

Eq

uiv

ale

nt

NCC

Cellobiose

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SummarySummary The economic, environmental, and The economic, environmental, and

strategic benefits of cellulosic ethanol are strategic benefits of cellulosic ethanol are great. great.

Time is ripe for commercial production of Time is ripe for commercial production of cellulosic ethanol.cellulosic ethanol.

Cost of the enzyme is a significant cost Cost of the enzyme is a significant cost factor in the cellulosic ethanol process.factor in the cellulosic ethanol process.

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oo

There is a room for improvement in the conventional FPU method.

The points to be addressed:

HPLC in place of reducing sugar. Calculate the extent of reaction in terms of the glucan equivalent of combined G1 and G2. Filter paper is still preferred over α-cellulose or Avicel because of consistency in property. Multiple-point (slope) method is preferred over one-point method for higher accuracy.

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Non-crystalline cellulose (NCC) can be used as a substrate to determine the relative activities of individual components of cellulase.

Hydrolysis of NCC by cellulase produces G1,G2,and cello-oligosacchrides (COS).

Formation of G1 and G2 from NCC may be taken as relative activity of exo-glucanase. Increase of reducing sugar in NCC may be taken as a measure of endo-glucanase activity.

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Cello-oligosaccharides (COS) can be used as Cello-oligosaccharides (COS) can be used as a substrate for identification of cellulase reactia substrate for identification of cellulase reactions.ons.

COS is hydrolyzed only by COS is hydrolyzed only by ββ-glucosidase.-glucosidase. (Endo and Exo-G cannot hydrolyze COS.)(Endo and Exo-G cannot hydrolyze COS.)

Hydrolysis of COS by cellulase is much slower Hydrolysis of COS by cellulase is much slower than NCC.than NCC.

ββ-Glucosidase works only on soluble substr-Glucosidase works only on soluble substratesates

(G2 & oligomeres).(G2 & oligomeres).

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AcknowledgementsAcknowledgements US Department of Energy Office of the BiomasUS Department of Energy Office of the Biomas

s Program (Contract DE-FG36-04GO14017)s Program (Contract DE-FG36-04GO14017) US EPA-TSE Program US EPA-TSE Program (No. RD-83164501) (No. RD-83164501) AU Team: Rajesh Gupta, Suma Peri, Yongming AU Team: Rajesh Gupta, Suma Peri, Yongming

Zhu, Hatem Harraz, T. H. Kim, Clayton SmithZhu, Hatem Harraz, T. H. Kim, Clayton Smith CAFI Team:CAFI Team:

Dartmouth College; Michigan State, Purdue, TDartmouth College; Michigan State, Purdue, Texas A&M; University of British Columbia; and exas A&M; University of British Columbia; and the National Renewable Energy Laboratorythe National Renewable Energy Laboratory

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Questions?Questions?Corn stover

Corn stover

Wood chip

Bagasse

Rice straw

Sawdust

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CellulaseCellulase Endo-Glucanase Endo-Glucanase

Cellulose Cellulose →→ Scarred Cellulose Scarred Cellulose

Exo-Glucanase (CBH)Exo-Glucanase (CBH)

Scarred Cellulose --- CellobioseScarred Cellulose --- Cellobiose

Beta-Glucosidase Beta-Glucosidase

Cellobiose --- GlucoseCellobiose --- Glucose

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Simplified Process SchematicsSimplified Process Schematics

Feed Handling

Utilities

SimultaneousSaccharification

& Co-FermentationPretreatment

Burner/BoilerTurbogenerator

ConditioningWaste WaterTreatment

Distillation &StillageTreatment

Storage

Corn Stover

Hydrolyzate BrothRecycle &Condensate

Waste Water

Ethanol

Cake

Biogas & Sludge

Waste Water

Enzyme

Recycle Water

Steam

Electricity

Steam

Solids

Liquor

Waste Water

S/L SepSyrup

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Economic Summary Economic Summary SheetSheet

Minimum Ethanol Selling Price $2.23

Ethanol Production (MM Gal. / Year) 47.9 Ethanol at 68°FEthanol Yield (Gal / Dry US Ton Feedstock) 62.1

Feedstock Cost $/Dry US Ton $53Internal Rate of Return (After-Tax) 10%Equity Percent of Total Investment 100%

Capital Costs Operating Costs (cents/gal ethanol) Feed Handling $7,500,000 Feedstock 85.4 Pretreatment $15,800,000 Biomass to Boiler 0.0 Neutralization/Conditioning $3,800,000 CSL 16.7 Saccharification & Fermentation $20,000,000 Cellulase 29.4 Distillation and Solids Recovery $23,000,000 Other Raw Materials 5.3 Wastewater Treatment $9,000,000 Waste Disposal 2.3 Storage $2,200,000 Electricity -20.2 Boiler/Turbogenerator $47,900,000 Fixed Costs 17.6 Utilities $4,800,000 Capital Depreciation 24.2Total Installed Equipment Cost $134,100,000 Average Income Tax 18.2

Average Return on Investment 43.7Added Costs $97,800,000 (% of TPI) 42% Operating Costs ($/yr)

Feedstock $40,900,000Total Project Investment $231,900,000 Biomass to Boiler $0

CSL $8,000,000Installed Equipment Cost/Annual Gallon $2.80 Cellulase $14,100,000Total Project Investment/Annual Gallon $4.84 Other Raw Matl. Costs $2,600,000

Waste Disposal $1,100,000Loan Rate N/A Electricity -$9,700,000Term (years) N/A Fixed Costs $8,500,000Capital Charge Factor 0.178 Capital Depreciation $11,600,000

Average Income Tax $8,700,000Denatured Fuel Prod. (MMgal / yr) 50.2 Average Return on Investment $20,900,000Denatured Fuel Min. Sales Price $2.15Denaturant Cost ($/gal denaturant) $0.572 Excess Electricity (KWH/gal) 5.04

Plant Electricity Use (KWH/gal) 2.94Maximum Yields (100% of Theoretical) Ethanol Production (MM Gal/yr) 82.6 Plant Steam Use (kg steam/gal) 32.0 Theoretical Yield (Gal/ton) 107.0 Boiler Feed -- LHV (Btu/lb) 2,244Current Yield (Actual/Theoretical) 58% Boiler Feed -- Water Fraction 0.516

All Values in 2002$Lime Prehydrolysis with Saccharification and Co-Fermentation

Lime - Corn Stover, Current Case

Ethanol Production Process Engineering Analysis

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Enzymatic Hydrolysis of Cello-Enzymatic Hydrolysis of Cello-oligosaccharidesoligosaccharides

Sp CP-A (15 FPU/g glucan)

0%2%4%6%8%

10%12%14%

0 20 40 60 80 100 120

Time (Hours)

% G

luca

n Eq

uiva

lent Glucose

Cellobiose

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e) 1 FPU

0%

2%

4%

6%

8%

10%

12%

0 5 10 15 20

Time, min

% H

yd

roly

sis

f) 1 FPU

0%

5%

10%

15%

20%

25%

30%

0 0.5 1 1.5 2

Time, hr

% H

yd

roly

sis

-Cellulose

Treated -Cell.

Enzymatic Hydrolysis of Crystalline and Enzymatic Hydrolysis of Crystalline and Non-Crystalline CelluloseNon-Crystalline Cellulose

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Estimation of Initial SlopesEstimation of Initial Slopes (G1 + G2)(G1 + G2)

Avicel Filter paper

Sp CP-A (0.06ml/g glucan)

y = 0.0579x + 0.0356

R2 = 0.9892

0%

5%

10%

15%

20%

0 0.2 0.4 0.6 0.8 1 1.2

Time (Hours)

%G

luca

n Eq

uiva

lent

Sp CP-A (0.06ml/g glucan)

y = 0.0734x + 0.0044

R2 = 0.9549

0%

5%

10%

15%

20%

0 0.2 0.4 0.6 0.8 1 1.2

Time (Hours)%

Glu

can

Equi

vale

nt