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Recovery and Purification of Bio-Products (Chapter 11, M. Shular, textbook). Strategies to recovery and purify bio-products Solid-liquid separation Cell disruption Separation of soluble products Finishing steps for purification. Recovery and Purification of Bio-Products.
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Recovery and Purification of Bio-Products(Chapter 11, M. Shular, textbook) • Strategies to recovery and purify bio-products • Solid-liquid separation • Cell disruption • Separation of soluble products • Finishing steps for purification
Recovery and Purification of Bio-Products • Strategies to recover and purify bio-products Unique characteristics of bioseparation products: - The products are in dilute concentration in an aqueous medium, e.g therapeutic protein 0.01mg/L. - The products are usually temperature sensitive. - There is a great variety of products to be separated. - The products can be intracellular, often as insoluble inclusion bodies. - The physical and chemical properties of products are similar to contaminants. - Extremely high purity and homogeneity may be needed for human care.
Fementer Solid-liquid separation Cell products Cells Supernatant Recovery Cell rupture Purification Cell debris Crystallization and drying Recovery and Purification of Bio-Products • Strategies to recovery and purify bio-products
Fementer Solid-liquid separation Cell products Cells Supernatant Recovery Cell rupture Purification Cell debris Crystallization and drying Recovery and Purification of Bio-Products • Strategies to recovery and purify bio-products
Recovery and Purification of Bio-Products • Liquid and solid separation - solid particles: mainly cellular mass, specific gravity 1.05-1.1. size (diameter): bacterial cells: 0.5-3 µm yeast cells: 5 -10 µm mold: 5-15 µm in diameter and 50-500 µm in length animal cells: 10 µm plant cells: 20 µm Methods: filtration and centrifugation
Filter cake Filter medium Slurry flow Filtrate Liquid-Solid SeparationFiltration Physical separation of solid particles from liquid or gas. a porous medium: allow fluid to pass through solid particles to be retained.
Liquid-Solid SeparationFiltration • Rotary vacuum filtration • Particle size: greater than 10 µm, yeast, mold, animal or plant cells. i.e. mycelium separation for antibiotics production or waste water treatment • Microfiltration • Particle size: 0.1 - 10 µm, bacterial and yeast cells. • Ultrafiltration • Size: 10-200 Å, Cell debris, macromolecules
Rotary Vacuum Filter • A rotary vacuum filter is a continuous filter partially submerged • in the slurry. • - A drum is covered with a filter medium. • Vacuum is applied to within the drum • As the drum rotates, the solid constituent is separated by retained on the porous medium • The liquid is drawn through the cake • into the inner filtrate pipes. • Each revolution consists of cake formation, • cake washing (if required), • drying and cake discharge.
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The rate of filtration (the flow of the filtrate) for (vaccum) filtration operation can be determined by(Bennet &Myers, Momentum, Heat and Mass Transfer, 1974, p221, the equation is from the mass balance of the cake.) Rotary Vacuum Filter
Rotary Vacuum Filter Assuming incompressible cake: constant α & constant pressure. Integrating the following equation (V at t, V=0 at t=0) yields
Rotary Vacuum Filter t/V V
Rotary Vacuum Filter To design a scaled-up rotary vaccum filter If given a total volume of fermentation broth Vb and required time tb to complete the filtration task at the large scale, determine the filter surface area. Based on the results from the smaller filter (incompressible cake: same α, medium & pressure drop):
Rotary Vacuum Filter For incompressible cake: constant α. If filtration rate is constant,
Liquid-Solid SeparationFiltration • Rotary vacuum filtration • Particle size: greater than 10 µm, yeast, mold, animal or plant cells. i.e. mycelium separation for antibiotics production or waste water treatment • Microfiltration • Particle size: 0.1 - 10 µm, bacterial and yeast cells. • Ultrafiltration • Size: 10-200 Å, Cell debris, macromolecules (antibiotics, proteins, polysaccharides)
Liquid-Solid Separation Filtration • Microfiltration & Ultrafiltration Use membrane as porous medium for filtration. Challenge: gel formation on the surface of membrane. Solution: cross-flow (tangential flow filtration) Pressure P1 Pressure P2 Feed in Feed out
Liquid-Solid Separation Filtration • Centrifugation - Particle size: 100-0.1 µm - more expensive than filtration - limited for scale-up - drive force: centrifugal force
Example (ex.11.1 in the textbook for solution) The following data were obtained in a constant-pressure unit for filtration of a yeast suspension: t(min) 4 20 48 76 120 V(L) 115 365 680 850 1130 Characteristics of the filter are as follows: A=0.28m2, C=1920kg/m3, μ=2.9X10-3 kg/m-s, α=4m/kg Determine: a) The pressure drop across the filter. b) The filter medium resistance. c) The size of the filter for the same pressure drop to process 4000L of cell suspension in 20 min.