Non-Lethal Oil Recovery Suitable For Biocatalytic Algal PlatformsR. Connelly1, S. Truscott3, K. O’Brien2, A.F. Seibert2, P. Kipp3

1University of Texas at Austin, Center for Electromechanics, Austin, TX2University of Texas, Separations Research Program, Austin, TX

3OpenAlgae LLC, Austin, TX

THE UNIVERSITY OF TEXAS AT AUSTIN

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.

Significance of the Study

Hypotheses

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.

Methods

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. A microporous hollow fiber membrane was pre-primed 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.

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.

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.

ConclusionsThe 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 technology2) The efficiency of oil removal is excellent; >95% of the oil is removed after a single pass despite the presence of cells3) 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.

Oil Droplets

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Methods / Results

Representative light micrograph of the experimental Chlorella/water/Isopar V mixture stained with Oil Red O.

Creation, visualization and separation of an experimental algae/water/Isopar V emulsion

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.

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.

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.

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