CRYSTALLIZATION UNIT

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CRYSTALLIZATIONUNIT

• Rachel Adams
• Jana Dengler
• Megan MacLeod
• Kyla Sask

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Outline

• Purpose of Crystallizer
• Methods of Crystallization
• Design Specifications
• Engineering Drawing
• Alternative Cost and Suppliers
• Alternative Processes
• Questions

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Purpose of Crystallizer

• Used to recover pure solids from solution
• Highly desirable end product because of
• Exceptional purity
• Ease of handling
• Long shelf life
• One of the final treatment steps in the
  purification and concentration of insulin
• 98 of the insulin must be crystallized

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Mechanism of Crystallization

• Crystal nucleation and amorphous precipitates are
  in competition during supersaturation conditions
• Nucleation favored by slowly exceeding the
  equilibrium point of saturation
• permits time for the protein structure
• to orient in a crystalline lattice

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Continuous or Batch Design

• Benefits of Continuous
• Can maintain solution in supersaturated state
• Large fluidized bed for crystallization
• Minimizes operation costs
• Minimize down time (startup and shutdown)
• Benefits of Batch
• Good when have low concentration of product, high
  viscosity or many impurities
• Can produce high quality crystal

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Methods of Crystallization

• Supersaturation liquid (solvent) contains more
  dissolved solids (solute) than can ordinarily be
  accommodated at that temperature
• Can be achieved by several methods
• Cooling
• Evaporation
• Solvent addition
• Precipitant Addition

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Cooling Method

• Concentrated solution gradually cooled below
  saturation temperature (50-60C) to generate a
  supersaturated state
• Yields well defined micron-sized crystals
• Shell and tube heat exchanger is used to cool
  solution

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Cooling Method

• Advantages
• High purity downstream
• Disadvantages
• Temperature change does not always have a
  positive effect on supersaturation in proteins
• Protein stability may be at risk
• Solubility can be relatively insensitive to
  temperature at high salt concentrations
• Cooling will only help reach supersaturation in
  systems where solubility and temperature are
  directly related

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Evaporation Method

• Solute dissolves in solution when heated to a
  certain temperature (75C)
• Slowly cooled until crystals precipitate
• Shell and tube heat exchanger is used to heat and
  cool solution

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Evaporation Method

• Advantages
• high purity levels downstream
• Disadvantages
• Vaporization chamber requires high pressures
• Protein viability very sensitive to high
  temperatures

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Solvent Method

• Solvents are generally good protein precipitants
• Their low dielectric constants lower the
  solvating power of their aqueous solutions
• Requires acidic solvent
• For crystallization, an insulin protein falls
  out of solution at isoelectric point
  pH 5.4-5.7

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Solvent Method

• Advantages
• Proteins viability not at risk due to temperature
  change
• Disadvantages
• Possible protein contamination due to
  insufficient downstream solvent recovery

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Addition of Zinc Ions

• In the presence of zinc ions, insulin proteins
  orient to form hexamer structures
• Zinc ions render insulin insoluble which results
  in micro-crystallization and precipitation
• Human Insulin Hexamer with Zinc ion

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Seeding Techniques

• Primary nucleation is the first step in
  crystallization - growth of a new crystal
• Can bypass primary nucleation (creation of new
  crystals) by "seeding" the solution
• Secondary nucleation is crystal growth initiated
  by contact
• Accelerated by "seeding" adding existing insulin
  crystals to perpetuate crystal growth

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Progression of Crystallization
http//www.cheresources.com/cryst.shtml
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Crystal Size and Growth Rate

• Crystal size distribution is important for the
  production process affects
• downstream processing
• solids transport
• caking and storage properties of the material
• Correct crystal size vital for economic
  production
• Crystals produced in commercial crystallization
  processes are usually small
• 30 to 100 um in diameter

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Crystal Size and Growth Rate

• Assumptions
• Continuous
• Constant-volume
• Isothermal
• Well-mixed
• Relates population density and crystal size

• Mechanism of crystal growth to determine crystal
  growth

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Crystallizer Design

• Addition of acidic solvent to decrease pH to
  achieve supersaturation
• Addition of Zinc ions to initiate Insulin
  precipitation
• Implementing of seeding technique
• Minimize heat variation to maintain protein
  stability
• Washing and extensive solvent recovery downstream

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Design Equations
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Proposed Design
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Engineering Drawing
http//sundoc.bibliothek.uni-halle.de/diss-online/
04/04H181/prom.pdf
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Costing Estimates

• Three costs involved
• Crystallizer unit
• Zinc Chloride Solution and Water
• Power Requirements

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Costing Estimates

• Crystallizer Unit www.matche.com

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Costing Estimates

• Crystallizer Unit

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Costing Estimates

• Zinc Chloride Solution
• Many suppliers
• 15.00 - 27.00 for 500g
• Power Requirements
• Canadian Hydro 8.99 cents/kWh (April, 2006)

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Crystallizer Suppliers

• GEA Niro Inc.
• Companies in over 50 countries
• Copenhagen, Columbia, Germany, USA
• GEA Kestner Evaporator/Crystallizer
• Swenson Technology Inc.
• Illinois, USA
• HPD Inc.
• Illinois, USA

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Alternative Processes

• For special drug purposes and when a zinc-free
  product is needed
• Alternative processes that can be used include
• Isoelectric Precipitation
• Gel Chromatography
• Ultrafiltration

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Isoelectric Precipitation

• Protein purification procedure that
  can be used with
  crystallization
  or on its own
• The pH of a mixture is adjusted to the pI of the
  protein to be isolated to selectively minimize
  its solubility

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Gel Filtration Chromatography

• Molecules are separated according to their size
  and shape
• Filtration column is filled with porous beads
• Solution passes through column
• Elution through the gel occurs in order of
  decreasing molecular masses

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Ultrafiltration

• Ultrafiltration used to concentrate
  macromolecular solutions
• Forced under pressure or by centrifugation
  through a semipermeable membranous disk
• Solvent and small solutes pass
• through the membrane, leaving
• behind a more concentrated
• macromolecular solution

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• QUESTIONS?