Extraction

1
Extraction

• Transfer of solute from one fluid to another
• Depends on the partition behavior of the solute
  between the phases

Fermentation broth Penicillin G impurities
water
MIBK
Impurities water
Penicillin G dissolved in MIBK
2
Applications of extraction

• Purification of antibiotics
• Purification of alkaloids
• Protein purification using aqueous two-phase
  systems
• Purification of peptides and small proteins
• Purification of natural dyes and pigments
• Purification of lipids
• Purification of DNA

3
Solvent systems

• Aqueous / organic systems
• Water/MIBK
• Water/acetone
• Water/chloroform
• Aqueous two-phase systems
• PEG/dextran
• PEG/potassium phosphate
• Supercritical fluid extraction

4
Solvent miscibility

• Ideally immiscible
• Suitable for extraction
• Partially miscible
• Composition dependent
• Various possibilities
• Could be used for extraction

5
Partially miscible solvent system
A, Solute
F
K
J
P
H
Q
C Extracting solvent
Original solvent B
L
6
Extraction
Feed
Rafinnate
Extractor
Extracting solvent
Extract
7
Extraction Sequence of events

• Mixing or contacting
• Phase separation
• Collection of separate phases

8
Aqueous two-phase extraction

• Special cased of liquid-liquid extraction
• Two immiscible aqueous phases are generated
  in-situ by addition of substances such as
  polymers and salts to the feed phase
• Two types of aqueous two phase systems
• Polymer-polymer two phase system
• e.g. dextran and PEG
• Polymer-salt two phase system
• e.g. PEG and KCl
• Phase separation is composition dependent

9
Aqueous two-phase extraction
Tie lines
PEG w/w
Dextran w/w

• Represent the compositions of the additives only
• Useful for determining what concentration of
  polymers and salts required
• Predict the polymer/salt content of the rafinnate
  and the extract phases
• Miscibility curve
• Tie-lines

10
Partition coefficient
Depends on physicochemical properties of
molecules and as phases PEG/dextran
system Polymer composition Solution pH
Molecular weight of solute Polymer and
salt Protein partitioning in the polymer phase
is favoured