Physico-chemical Surface Properties of Microalgae:...
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Solar Energy and Renewable Fuels Laboratory Physico-chemical Surface Properties of Microalgae: Cell-Surface and Cell-Cell Interactions Altan Ozkan and Halil Berberoglu* Mechanical Engineering Department The University of Texas at Austin 7 th Annual Algae Biomass Summit October 2, 2013, Orlando FL
Transcript of Physico-chemical Surface Properties of Microalgae:...
Solar Energy and
Renewable Fuels Laboratory
Physico-chemical Surface Properties of Microalgae:
Cell-Surface and Cell-Cell Interactions
Altan Ozkan and Halil Berberoglu*
Mechanical Engineering Department
The University of Texas at Austin
7th Annual Algae Biomass Summit
October 2, 2013, Orlando FL
Motivation: Surface Interactions of Algae Cells
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●Cell to Surface Interactions
oUndesired attachment of cells on surfaces (biofouling)
● Photobioreactors
● Filtration Systems
● Cooling towers
● Ship hulls
oDesired attachment of cells on surfaces
● Algal biofilm/ algal turf based cultivation systems
● Photosynthetic microbial fuel cells
●Cell to Cell Interactions
oBioflocculation
oRheological behavior of slurries
● Apparent viscosity
● Settling of flocs
Interaction Mechanisms of Cell Surfaces
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● Surface Interaction Mechanisms
o Lifshitz-van der Waals Interactions GLW
oElectrostatic Interactions GEL
oAcid-base Interactions GAB
● Extended Derjaguin, Landau, Verwey, Overbeek (XDLVO) Model
● Total Interaction Energy:
We need to know the physico-chemical surface properties of cells and surfaces
Physico-chemical Surface Properties of Algae
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● Surface free energy components o Lifshitz-van der Waals gLW, electron donor g-, electron acceptor g+
o Quantified using contact angle measurements and extended Young’s Equation:
● Sessile drop technique using three probe liquids: water, diiodomethane, formamide
● 9 measurements with each probe liquid, with standard deviation less than 3.9% in results
● Surface potential o Measured the zeta potential (z) of cells from electrophoretic mobility using a
Zeta Meter ● Fresh water species in BG-11, salt water species in ASP-M
● Recovered the surface potential (y) accounting for the double layer and hydration layer thicknesses
● 25 measurements for each species, with standard deviation less than 3.0% in results
● Free energy of cohesion of surfaces
DGcoh > 0 : Hydrophilic
DGcoh < 0 : Hydrophobic
Physico-chemical Surface Properties of Algae
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● Surface properties of 12 different microalgae including green algae,
diatoms, and cyanobacteria were quantified
Adsorption/Desorption Experiments
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● Conducted adsorption desorption experiments to validate the use of XDLVO model
● Algae: Chlorella vulgaris (UTEX 2714) and Botryococcus sudeticus (UTEX B2629)
● Substrata: Glass and ITO coated glass
0.35 mm thick PDMS with a gap at the
center for liquid flow
Material to be tested (Glass/ITO)
Polycarbonate top plate with two pipe to tubing
adapter
100 μm 100 μm
flushing
Procedure:
Let the cells settle for 2 h
Flush flow rates: from 4.5 mL/min to 31.5 mL/min
Corresponding shear rates: 100 to 700 s-1
Calculated the drag and lift forces on the cells.
Adsorption/Desorption Experiments
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●Results
XDLVO model agreed well with experimental observations of adhesion strength
Applications of XDLVO Model: Cell-Surface Interactions
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● Applied the XDLVO model for analyzing the interactions of different
algal species and different materials of interest
Applications of XDLVO Model: Cell-Surface Interactions
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● Applied the XDLVO model for analyzing the interactions of different
algal species and different materials of interest
Applications of XDLVO Model: Cell-Cell Interactions
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● Applied the XDLVO model for analyzing the interactions of different
algal species with each other
Applications of XDLVO Model: Effects of pH and Ionic Strength
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● Changes in medium pH and ionic strength affect the electrostatic
interactions
At the ionic strength considered, y is:
16.1, −9.3, −16.9, and −22.1 mV at
pH 2, 4, 6, and 8, respectively. PZC is pH 2.9
The availability of the counter ions increases with
increasing ionic strength, decreasing the thickness
of the electric double layer.
Presence of multivalent cations also affect polar
Interactions, making the surfaces more hydrophobic
Conclusions and Future Work
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● Physico-chemical surface properties of 12 different microalgae species have been experimentally measured o Strong correlation between benthic cultures and hydrophobic surfaces
● XDLVO model has been established to agree well with experimental observations o Acid-base (polar) interactions play a major role in algal attachment
o Cell to cell and cell to surface interactions can be predicted using this model
● Future work includes: o Characterization of EPS and its effects
o Multi-microorganism scenarios
1. Ozkan A., Berberoglu H., 2013, Physico-chemical surface properties of microalgae, Colloids and
Surfaces B, Vol. 112, pp. 287-293. DOI: http://dx.doi.org/10.1016/j.colsurfb.2013.08.001
2. Ozkan A., Berberoglu H., 2013, Adhesion of algal cells to surfaces, Biofouling, Vol. 29, pp. 469-
482. DOI: http://dx.doi.org/10.1080/08927014.2013.782397
3. Ozkan A., Berberoglu H., 2013, Cell to substratum and cell to cell interactions of microalgae,
Colloids and Surfaces B, Vol. 112, 302-309. DOI: http://dx.doi.org/10.1016/j.colsurfb.2013.08.007
This presentation is based on the following recent work:
Solar Energy and
Renewable Fuels Laboratory
THANK YOU!
The University of Texas at Austin
Mechanical Engineering Department
Solar Energy and Renewable Fuels Laboratory
www.solarfuels.net
7th Annual Algae Biomass Summit
October 2, 2013, Orlando FL
Altan Ozkan
Halil Berberoglu
● The National Science Foundation (CBET-1125755)
Stages of Biofilm Formation on Surfaces
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●Formation of biofilms can be considered in four stages
I. Adsorption of organic matter such as EPS
I II III IV
II. Initial adhesion of algae cells
III. Anchoring or irreversible adhesion
IV. Growth of the algal biofilm
