determination of mass transfer limitations in e. coli encapsulated beads
DESCRIPTION
Determination of mass transfer limitations in E. coli encapsulated beads. From Team M-4 Leader: Waifong Chan George Hammer Yimin Tang. Introduction of Cell Encapsulation. Commonly employed in bioprocesses to encapsulate bioactive species. Immobilize the cells. - PowerPoint PPT PresentationTRANSCRIPT
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Determination of mass transfer limitations in E. coli encapsulated
beadsFrom Team M-4
Leader: Waifong ChanGeorge Hammer
Yimin Tang
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Introduction of Cell EncapsulationCommonly employed in bioprocesses
to encapsulate bioactive species.
Immobilize the cells.
Protect the cells from shear forces.
Increase the surface area and allow
higher permeability.
Promote the level of cell viability.
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Project Overview
To examine one method for encapsulating cells in alginate beads.
To demonstrate the parameters which control the bead size.
To determine the reaction is limited either by the reaction rate or the mass transfer limitation.
“I would like to know what parameters may control the average diameter of the beads produced and whether encapsulation imposes mass-transfer limitations for the bacteria.” -Dr. Ima Manager.
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Previous WorkPhase-1:
Safety Standard operating procedureBeads diameter regarding the changing flow
rate.
Phase-2: determine the change of oxygen uptake by changing…Bead sizeE. coli concentration
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Theory of mass transfer limitationAssumption:Steady StateParticle is isothermalMass transfer by diffusion onlyDAE, effective diffusivity is constantParticle is homogeneousZero-kinetic
Reaction rate is independent on the substrate concentration.
Reaction rate = rate constant * particle volume
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Thiele ModulusObservable Thiele Modulus
Where: Vp= catalyst volume Sx = External surface area R= radius of bead rA,obs= unit oxygen uptake rate =
DAe= Effective Diffusivity of oxygen in the beads
CAs= Concentration of oxygen at the surface
AsAe
obsA
CD
rR ,2
3
AsAe
obsA
x
p
CD
r
S
V ,
2
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Weisz criteria
ηi: the internal effectiveness factor
ηi = (observed rate)/(rate that would occur if CA = CAS)If ηi ≈ 1, negligible mass transfer limitationIf ηi < 1, mass transfer deficiencies throughout
the bead
13. i13 i
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ApparatusRing standCentrifuge tubeSyringeAir jetAir rotameterPetri-dish
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Apparatus (Cont’d)
Oxygen Probe
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Methods Prepare solution---- 0.5ml 3% Sodium Alginate & 0.5ml E.Coli
Transfer solution----To a syringe plunger with a 22 gauge needle
Secure syringe----use rubber band that needle protrudes 1 mm
Prepare Petri dish----filled with CaCl2
Turn on air jet----to 60 SCFH and place it coaxially with syringe
Collect beads----record volume used and drain CaCl2
Calibrate oxygen probe
O2 calibration----in 30ml LB & beads mixture with parafilm
Record O2 concentration----on every 5 min after stabilized
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Results (Bead size)Air Flow 60 SCFH 50 SCFH
Diameter Sample 1 225µm 275µm
Diameter Sample 2 280µm 275µm
Diameter Sample 3 328µm 300µm
Diameter Sample 4 300µm 330µm
Average Diameter 282µm 295µm
Fig.1: Alginate bead at air flow rate of 60 SCFH.
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Results (oxygen uptake)
0 50 100 150 200 250 300 3503
3.5
4
4.5
5
5.5
6
f(x) = − 0.00805238095238095 x + 5.28619047619048R² = 0.874486209815902
Dissolved oxygen content (mg/L)
Time elapsed (s)
Dis
solv
ed o
xygen
con
ten
t (m
g/l
)
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Results (oxygen uptake)Average Bead Diameter (m)
Average Unit Bead Volume (m3)
Number of Beads used
Overall Oxygen Uptake Rate (mg/l)
rA,obs
(mg/l)
2.82E-04 1.17E-11 8.52E+04 8.10E-03 9.51E-08
R (m) 1.41E-04
rA,obs (mg/l) 9.51E-08
Dae (m2/s) 2.56E-09
Cas (mg/l) 5.76
Φ 1.42E-08
Ф < 0.3
ηi = 1negligible mass transfer limitation
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Results from other literaturesFrom Xiaoming Xu et al[4]
Mass transfer is inversely related to beads’ diameter.
Some suggest that[2] [3]
Needle inside diameter and the viscosity of the alginate also contribute to the variability of bead’s diameter.
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ConclusionThe main parameter to determine the bead
size is the co-axle air flow rate.Higher flow rate corresponds to smaller
beads but in better spherical shape.Using Thiele modules and Weisz criteria,
alginate beads was demonstrated to have no mass transfer limitation.
Other literatures shows that smaller size of alginate beads can have higher mass transfer.
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RecommendationsUsing at least 1 ml of alginate beads in
order to observe significant change in
oxygen consumption.
Install a heater to incubate alginate
beads at 37 °C.
Using magnetic stirring bar with suitable
glassware to minimize the vibration
created by the oxygen probe.
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References1. Team M-5, Phase II Memo, 04/05/2010
2. G. W. Vandenberg, C. Drolet, S. L. Scott1 and J. de la Noüe, “Factors affecting protein release from
alginate –chitosan coacervate microcapsules during production and gastric/intestinal simulation Journal of
Controlled Release”, Volume 77, Issue 3, 13 December 2001, pages 297-307.
3. aUlf Pr¨usse*, bLuca Bilancetti, cMarek Bučko, dBranko Bugarski, eJozef Bukowski, cPeter Gemeiner, eDorota
Lewi´nska, dVerica Manojlovic, fBenjamin Massart, b Claudio Nastruzzi, gViktor Nedovic, hDenis Poncelet,
iSwen Siebenhaar, hLucien Tobler, bAzzurra Tosi, cAlica Vikartovska, aKlaus-Dieter Vorlop., “Comparison of
different technologies for alginate beads production”, Chemical Papers 62 (4) 364–374 (2008)
4. Xiaoming Xu, Philip S. Stewart *, Xiao Chen Transport limitation of chlorine disinfection of Pseudomonas
aeruginosa entrapped in alginate beads, Biotechnology and bioengineering 1996, vol. 49, no1, pp. 93-100 (25
ref.) 1996 John Wiley & Sons, Inc
5. Rigini M Papi, Sotiria A Chaitidou, Fotini A Trikka and Dimitrios A Kyriakidis, Encapsulated Escherichia
coli in alginate beads capable of secreting a heterologous pectin lyase, Microbial Cell Factories 2005, 4:35.
6. Mehmetoglu, U. "Oxygen Diffusivity in Calcium Alginate Gel Beads Containing Gluconobacter Suboxydans."
Artificial Cells, Blood Substitutes, and Biotechnology 24.2 (196): 91‐106. Web. 28 Mar 2010.
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