R.
1
Connelly ,
S.
3
Truscott ,
K.
2
O’Brien ,
A.F.
2
Seibert ,
P.
3
Kipp
1University of Texas at Austin, Center for Electromechanics, Austin,
2University of Texas, Separations Research Program, Austin, TX
3OpenAlgae LLC, Austin, TX
TX
Significance of the Study
Methods / Results
A host of strategies are being explored to develop
biocatalysts that can convert carbon inputs into
renewable oils. Designer organisms that produce
and secrete fungible oils are advancing out of the
lab and into pilot scale production. The various
biotech-based platforms already make oils at prices
that can compete in established niche markets. To
achieve its full commercial potential, a platform
based on a designer photosynthetic organism that
can convert CO2 to oil and secrete it must be able
to recover the oil without harming the organism.
We have developed a new concept in oil recovery
that achieves oil coalescence in the presence of
algal cells. The technique is remarkably efficient
and inexpensive and relies on commercially
available, highly-scalable, proven membrane
technology.
Creation, visualization and separation of an experimental algae/water/Isopar V emulsion
A
B
Oil Droplets
Representative light micrograph of the experimental
Chlorella/water/Isopar V mixture stained with Oil Red O.
Representative light micrograph of the experimental
Chlorella/water/Isopar V mixture stained with Oil Red O
after passing through the oil recovery membrane once.
Droplets of Isopar V stain red.
1.2
98% removal
An experimental insoluble oil/water/algae
emulsion can be separated into insoluble oil and
water/algae fractions with a single pass through
the OpenAlgae oil recovery membrane process.
A single pass through the membrane will not
materially impact the viability of the cells.
5
1.0
4.5
4
3
2
Oil in the emulsion before and after passing
through the membrane was extracted using
solvent. The solvent was boiled off and the
remaining oil was weighed. Untreated aliquots of
Chlorella and those that passed through the
membrane were regrown to assess impacts on cell
health.
0.8
0.7
0.5
1
0
Raw Algae
(No Isopar V
Added)
influent
containing
Isopar V
.08
Influent
Containing
Isopar V
Effluent,
Single
Pass
0.4
0
1
2
3
4
5
6
7
8
Days in Culture
Methods
A microporous hollow fiber membrane was preprimed with Isopar V. The mixture of Isopar
V/water/algae was passed through the membrane
at a rate of 1 gpm to evaluate oil removal.
0.9
0.5
Isopar V, collected from 50 mL aliquots (in triplicate) of the experimental
emulsion prior to and after passing through the membrane, was weighed to
assess oil removal (a sample of algae without Isopar V added is shown for
reference). 98% of the oil in the emulsion was removed by the membrane.
Chlorella sp. was grown in F/2 medium under
artificial lighting. 10 L of culture (~0.45 mg/L algae)
were removed to a separate vessel. 1 L of Isopar V
(ExxonMobil), a model fungible diesel
hydrocarbon, was vigorously integrated into the
algae by constant mixing; oil was visualized by Oil
Red O staining and light microscopy.
Membrane
Control
1.1
Absorbance at 680 nm
Hypotheses
Mg of Oil Recovered from the Algae Stream
6
Regrowth of Chlorella following a single pass through the membrane.
50 mL aliquots (in triplicate) were regrown following a single pass
through the membrane, with no supplemental nutrients added.
Untreated samples of Chlorella from the same source were grown in
parallel for comparison.
Conclusions
The OpenAlgae oil recovery technique was designed to recover oils liberated from lysed algae cells. This
study extends the basic oil/water/algae separation technique to biocatalyst platforms. The results show:
1) An experimentally generated emulsion can be efficiently removed from the algal stream using the membrane technology
2) The efficiency of oil removal is excellent; >95% of the oil is removed after a single pass despite the presence of cells
3) Passing through the membrane does not inhibit cell growth or viability
These studies demonstrate that fungible, drop-in hydrocarbon molecules can be easily and rapidly recovered
from water and away from algae using available technology.
A bio-catalyst platform that makes micron-sized oil droplets could use this inexpensive, scalable and proven
technique to recover oil and keep the designer microbe alive to produce additional product.
Future Experiments
These studies can be extended to demonstrate recovery of different oil-soluble products (i.e., TAG).
These studies can be extended to demonstrate removal of oil from higher stability emulsions with smaller oil
droplets.
These studies can be extended to demonstrate that the technique can be applied to non-algae biocatalyst
platforms making drop-in molecules.
THE UNIVERSITY OF TEXAS AT AUSTIN