L9: Percipitation, Extraction, Ion exchange

Question 1

What are the two main methods of synthesizing succinic acid?

Answer 1

Chemical synthesis via butane oxidation and fermentation from sugar.

Question 2

What is the theoretical carbon yield of succinic acid from sugar via fermentation?

Answer 2

Greater than 1, based on sugar.

Question 3

What are the downstream processing (DSP) requirements for small molecules like succinic acid?

Answer 3

High product concentration, high downstream yield, and easy separation from water and other components.

Question 4

What are the typical challenges in succinic acid recovery from fermentation?

Answer 4

Removing cells, cell debris, proteins, and separating succinic acid from water, fermentation broth, and byproducts (e.g., acetic, lactic, pyruvic acids).

Question 5

What pH challenges are associated with succinic acid fermentation?

Answer 5

Succinic acid exists as a salt at neutral pH, complicating crystallization and separation.

Question 6

What are the three main routes for recovering succinic acid from fermentation?

Answer 6

Precipitation, electrodialysis, and liquid-liquid extraction.

Question 7

What is the principle behind precipitation in DSP?

Answer 7

Solutes are brought out of solution as solids, often through pH adjustment, salt addition, or the use of organic solvents.

Question 8

Why is ammonium sulfate commonly used in protein precipitation?

Answer 8

It has high solubility, low density for centrifugation, and stabilizes proteins in precipitated form for long-term storage.

Question 9

What are the steps in the precipitation process?

Answer 9

Mixing, nucleation, growth by diffusion, and growth by fluid motion.

Question 10

How does ionic strength or temperature affect flocculation during precipitation?

Answer 10

Increasing ionic strength or decreasing temperature minimizes electrostatic repulsion, enhancing flocculation.

Question 11

What are the three common designs for precipitation reactors?

Answer 11

Batch reactor, tubular reactor, and continuous stirred-tank reactor (CSTR).

Question 12

What is electrodialysis, and how is it used for succinic acid recovery?

Answer 12

It separates molecules through a membrane based on charge, driven by an electrical potential difference.

Question 13

What are the key advantages and challenges of using liquid-liquid extraction in DSP?

Answer 13

It is efficient for separating solutes, but its effectiveness depends on solvent selection, solute properties, and phase miscibility.

Question 14

What is the distribution coefficient (K), and why is it important in liquid-liquid extraction?

Answer 14

It defines solute distribution at equilibrium between two phases; higher K values improve extraction efficiency.

Question 15

What are aqueous two-phase extraction systems, and when are they used?

Answer 15

Systems made of water-soluble polymers or polymer-salt combinations for non-denaturing separation of proteins and cells.

Question 16

What is the significance of countercurrent flow in multi-stage extraction processes?

Answer 16

It maximizes the solute concentration gradient, enhancing recovery efficiency.

Question 17

What are common extractors used in biotechnology for liquid-liquid extraction?

Answer 17

Agitated extraction columns and centrifugal extractors.

Question 18

What are the advantages of precipitation for protein purification?

Answer 18

It reduces volume, simplifies equipment needs, is inexpensive, and stabilizes proteins for storage.

Question 19

How does pH adjustment aid in protein precipitation?

Answer 19

Proteins precipitate at their isoelectric point (pI), minimizing solubility.

Question 20

Why is PEG (polyethylene glycol) used in protein precipitation?

Answer 20

Because it produces a nonionic environment that encourages aggregation, it decreases the solubility of proteins.

Question 21

What are the benefits of batch reactors in precipitation processes?

Answer 21

They produce compact and regular protein precipitates.

Question 22

How does the tubular reactor design compare to batch reactors for precipitation?

Answer 22

Tubular reactors offer continuous operation with similar particle size distribution as batch reactors over time.

Question 23

What factors influence the partition coefficient in liquid-liquid extraction?

Answer 23

Molecule size, pH, solvent type, temperature, and phase composition.

Question 24

Why is crystallization desirable for succinic acid recovery?

Answer 24

It provides a pure, solid product but requires high concentrations to achieve supersaturation.

Question 25

What is the primary goal of DSP in bioprocessing for small molecules?

Answer 25

To achieve high product concentration, yield, and purity while minimizing costs and complexity.