What is biorefining?

Question 1

What is a biorefinery?

Answer 1

Integrates biomass conversion processes and equipment to produce fuels, power, heat and value-added chemicals (ethanol) from biomass.

Question 2

What are carbohydrates?

Answer 2

Polymers composed of sugars.

Monomer sugars: glucose, fructose, galactose,

Dimer sugars: maltose, sucrose, lactose

Question 3

What is starch?

Answer 3

Made up of glucose monomers.

Made up of amylose and amylopectin

Enzymes breakdown - amylase

Question 4

What is amylose?

Answer 4

Smaller polysaccharide which is linear having alpha 1-4 linkage between glucoses.

Question 5

What is amylopectin?

Answer 5

The larger component of starch which is highly branched. This polymer has amylose as a base but has branching connected by alpha 1-6 linkage.

Question 6

What are some sources of starch?

Answer 6

Cereal grain seeds like corn, wheat, Tubers and Roots like potato, peas, sago.

Question 7

What is lignocellulosic resource?

Answer 7

Woody and agricultural resource, that isn’t water soluble and hard to digest. Consists of Cellulose, Hemicellulose, and Lignin.

Question 8

What is Cellulose?

Answer 8

Structural component of woody plants made of sugar polymers which has a beta-D-linkage.

Have both crystalline and amorphous regions.

Question 9

What are some recalcitrant properties of cellulose?

Answer 9

Crystallinityy of cellulose makes it harder for enzymes to break it down.

Requires 320C, 25MPa to become amorphous in water.

Question 10

What base components make-up hemicellulose?

Answer 10

Xylose, mannose, galactose, rhamnose, arabinose and C5 sugars.

Question 11

How can hemicellulose be extracted & broken down?

Answer 11

Soluble in water so it can be extracted

Dilute acid/base can hydrolyze hemicellulose because of its amorphous structure

Question 12

What are the steps to extract starch from plants?

Answer 12

a) Plant material is chopped into tiny pieces
b) Rasped to break cell open
c) Starch is rinsed & filtered

Question 13

What is the difference between flour and starch?

Answer 13

Flour undergoes minimal processing

While starch is heavily processed

Question 14

If the desired products from starch are gluten feed, gluten meal and corn oil, what type of milling process should be used? Why is this process used and will it cost more or less?

Answer 14

Wet milling should be used

Produces larger variety of products at a higher operating cost

Question 15

What is the major difference between dry and wet milling

Answer 15

Dry milling is used for larger ethanol productions and operates at lower costs

Wet milling is used when a variety of products are desired, and hence operate at a higher cost

Starch in wet milling doesn’t go through drying process after steeping

Question 16

What part of the corn should be used if corn oil is desired product?

Answer 16

Corn germ

Question 17

Why was there a need to replace acid hydrolysis of starch with enzymatic hydrolysis?

Answer 17

Acid hydrolysis required corrosion resistant reactors

Required more energy for heating

Difficult to control

Question 18

What are the stages in starch conversion? Summarize each step?

Answer 18

1) Gelatinisation
- Dissolution of starch, forming viscous suspension (amorphous gel)
Heated for 5 min @ 100-105C in water

2) Liquifaction
- Enzymes hydrolyze viscous gel, hence decreasing viscosity
time: 1-2hrs @ 90-95C
- Convert starch to dextrins (smaller glucose polymers)

3) Saccharification
- Complete hydrolysis to required Dextrose Equivalent (DE)
- Max temperature of 95C is not exceeded

Question 19

What are the enzymes involved starch hydrolysis? What function do they serve?

Answer 19

Amylase

• breaks alpha 1-4 bonds
• alpha amylase cleaves 1-4 bonds at random points
• beta amylase cleaves 1-4 bonds at the end of the chain

Pullulanase
- breaks alpha 1-6 bonds

Glucoamylase
- Converts maltose to glucose

Question 20

What is an oligosaccharide? What function does it serve?

Answer 20

• Polymers containing 3-10 simple sugars

- Used in cell recognition & cell binding

Question 21

Define Metabolism

Answer 21

Overall sum of enzyme catalyzed chemical reactions in biological systems

Question 22

Saccharomyces cerevisiae is the most conventional ethanol producer. Under what conditions can this organism be used for fermentation & what limitations?

Answer 22

Must be done in anaerobic conditions (or anoxic)

Can only assimilate C6 sugars

Question 23

Which type of organisms are used for fermentation? What are the molecules formed as a result of fermentation by these organisms?

Answer 23

Facultative anaerobes, strict anaerobes & aero-tolerant anaerobes are used for fermentation

1 glucose -> 2 ATP + 2 Ethanol

Question 24

The yeasts Schizosaccharomyces pombe & Kluyveromyces marxianus carry which respective advantage in fermentation?

Answer 24

S. pombe can tolerate high salt content (high osmotic pressure)

K. marxianus can tolerate high temperatures (thermophilic conditions), allowing for increased rate of metabolism & lower refrigeration requirements

Question 25

What are the disadvantages of fermenting with yeast?

Answer 25

Can only ferment mono or disccaharides Cannot assimilate cellulose, hemicellulose or lignin directly Not all yeasts can ferment C5 sugars

Question 26

What is diauxic growth? Define each step.

Answer 26

Diauxic growth is two-staged cell growth caused by the presence of two sugars, seen in yeasts and/or bacteria that can ferment both C5 & C6 sugars Stages in Diauxic growth - Fermentation/metabolism of C6 sugars until depletion - Lag phase: Synthesis of enzymes for C5 fermentation/metabolism - Fermentation/metabolism of C5 sugars until depletion

Question 27

What advantage does using a bacteria such as zymomonas mobilis have over yeasts? What type of bacteria is it?

Answer 27

Higher ethanol yields caused by lower cell yield, increasing amount of ethanol obtained from same substrate Facultative anaerobe

Question 28

What are the different pathways that bacteria & yeasts use for fermentation? What are the resulting products?

Answer 28

Bacteria such as Z. Mobilis make use of Entner-Duodoroff pathway 1 Hexose -> 1 ATP + 2 Ethanol Yeasts such as S. Cerevisiae make use of the Embden Meyerhoff-Parnas pathway 1 Glucose -> 2 ATP + 2 Ethanol

Question 29

What are the advantages & disadvantages of using a bacteria such as Z. Mobilis?

Answer 29

Advantages - High ethanol tolerance - High optimal production temperature - Easily genetically manipulated Disadvantages - Can only ferment glucose, fructose & sucrose - Sucrose based media leads to levan (increases viscosity) and sorbitol formation

Question 30

What is the goal of genetically modified organisms?

Answer 30

- Hydrolyze starch & ferment glucose, without addition of amylases - Ferment pentose - Eliminate controls that inhibit hyper-production of desired products - Consolidated bioprocessing (Removal or combination of steps ie Liquefaction & Saccharification into one step or total removal) - Combine bacterial enzymes into yeast

Question 31

What is the difference between 1st and 2nd generation biofuels?

Answer 31

1st Gen - Made from sugar and vegetables 2nd Gen - Made from biomass sources - any source of organic carbon that is renewed as a part of the carbon cycle - lignocellulosic biomass

Question 32

Why does lignin pose a problem when using lignocellulosic biomass?

Answer 32

- Lignin is a protective barrier of plants | - Prevents cell destruction therefore must be removed to access cellulose and hemicellulose

Question 33

What are the main goals of pre-treatment?

Answer 33

- Remove lignin - Reduce crystallinity of cellulose - Increase porosity of the biomass

Question 34

What are the requirements for pre-treatment?

Answer 34

- Improve the formation of sugars (or subsequent formation) - Must not degrade/destroy carbohydrates in biomass - Avoid formation of inhibitory products = inhibitory to hydrolysis or fermentation process - Cost effective

Question 35

What are the different categories of pre-treatment?

Answer 35

``` Physical: milling, grinding Physio-chemical: Steam explosion Chemical: dilute alkali/acid Biological Electrical ```

Question 36

It is required to pre-treat biomass using a chemical method that is lowest hazard to the environment. Which method should be selected? Describe the process.

Answer 36

Ozonolysis should be selected - Reactions are carried out at RT & normal pressure - Degrades lignin and hemicellulose - Ozone decomposed by catalytic bed or by increasing temperature

Question 37

A company narrows down its choices to 2 pre-treatment methods: AFEX & ARP. The company uses a wide variety of biomass, and requires lignin to be the main component in the biomass to be degraded. Which of the two processes should be chosen? Why?

Answer 37

- Ammonia Recycle Percolation method should be chosen - ARP uses aqueous ammonia that reacts primarily with lignin, causing depolymerization (cleaves lignin from carbs) - AFEX only a small amount of solid material is solubilized = almost no lignin or hemicellulose removed

Question 38

A customer wants to use the steam explosion pre-treatment method for a bioprocessing plant. What are some objections you would bring up before the customer makes the purchase?

Answer 38

- Destruction of xylan fraction (destroys some amount of carbs in biomass) - Incomplete destruction of the lignin matrix - Formation of inhibitory compounds - Pre-trated biomass requires washing

Question 39

A bioprocessing plant uses a feedstock biomass that conatins residual lignin (6.4wt% - 27.4wt%). The company requires that most products be recovered after pretreating its biomass. Which process should be chosen? Why? Under what conditions does this method operate?

Answer 39

Lignol process should be used - Used for residual lignin content - Lignin recovered as precipitate = Achieved by flashing the pulp liquor to atmospheric pressure - Hemicellulose sugars and furfural are recovered recovered from a water-soluble stream - 50:50 ethanol water blend at 200C & 400psi extracts most of lignin