Applying flow cytometry equipped with a sorting module enables scientists to separate cells that differ in cell size, morphology, or fluorescence being derived from photosynthetic pigments (autofluorescence) or from applied fluorescent probes. This technology s key to algae optimization, and the use of algae are in turn important for the production of biofuels.
Algal-based biofuels have several advantages, such as offering a carbon neutral combustion and for generating a fuel suitable for many vehicles.
To look into this topic more deeply, Digital Journal spoke with Dr. Babetta L. Marrone from the U.S. Los Alamos National Laboratory.
Digital Journal: What is the current state of biofuel development?
Babetta L. Marrone: The biofuel industry has grown tremendously in the past twenty years; our goal is to replace 25 percent of the US transportation fuel market by 2040.
DJ: Which forms of biofuels are most promising?
Marrone: There are a variety of fuel types that can be made from biomass. These include ethanol (as a blend), gasoline, diesel, and jet fuels, mostly derived from biomass and referred to as “drop-in” fuels. Essentially, biomass-derived fuels may directly replace petroleum-based fuels using the same infrastructure that is already in place for conventional petroleum-based fuels. Of the types of biomass feedstocks that can be used to produce biofuels, our research focuses on microalgae.
Algae has advantages over other types of biomass. As a “crop” for biofuel, it can be grown on marginal lands with water not suitable for agriculture in a variety of environments on minimal acreage. However, growing algae also has some challenges that we are addressing through our research in order to make algae-based biofuels more affordable.
DJ: What are the main limitations impacting on algal biofuel development?
Marrone: The main challenge is that the cost of algae cultivation and processing (harvesting and conversion to fuel) needs to be substantially reduced if we want to compete with petroleum-based fuels. Some of the factors that affect the cost of producing algae for biofuels are technical/operational, while others are focused on the biology:
The algae species that we cultivate need to be more productive on a per cell basis;
Cultivation needs to be able to occur throughout the year.
There is also the challenge of scaling up production; what we observe in the lab is not necessarily directly transferred to outdoor conditions.
We are trying to address these technical challenges through our research.
Another challenge is that we need to produce other bioproducts in addition to fuel in order to bring down the overall costs of algae cultivation and harvesting. Producing a more valuable co-product, alongside the fuel product offsets the cost of algae production. In a similar way, the petroleum industry makes a large percentage of their profits using a small part of a barrel of oil for making chemicals and materials.
DJ: How can these issues be overcome, and appropriate species of algae optimized?
Marrone: One area that we focus on, related to the publication, is on strain improvement. We start with algal strains that have proven to be good factories for making the oils or lipids needed for biofuels. Then we work to improve their production of lipids either through genetic engineering or through other methods like cell sorting of individual cells with high productivity and cultivating those isolates.
DJ: How does fluorescence-based, high-throughput flow cytometry work?
Marrone: Flow cytometry and fluorescence-activated cell sorting are single cell analysis methods that were developed at Los Alamos in the 1960’s. Cells are forced into a flowing sample stream of single cells that moves rapidly past a laser beam. The laser activates a fluorescent tag on the cell that is bound to a specific cell constituent (lipids, esterase enzyme, reactive oxygen species, etc).
The cells move at a high rate of speed-thousands of cells per second. Data from many thousands of cells are collected and their fluorescence intensities, corresponding to specific cell properties or phenotypes, are measured and compared. The measurements can be coupled with cell sorting, so that cells with high fluorescence, for example, can be sorted out of the general population in real-time and collected for further study.
DJ: What are the main insights from your recent research paper?
Marrone: Our research paper shows our success in developing methods to rapidly monitor the health and function of cultivated algae. Our methods are useful to researchers who are developing new or improved algae strains by providing them with the tools to measure a wider range of functional cell features associated with algae performance during cultivation. These tools can be used to assess changes in algae function associated with different cultivation or environmental conditions, and in response to genetic engineering efforts. Tools like this are important to advance technologies for optimizing algae growth and productivity for biofuels or bioproducts. As they say: “You can’t manage what you can’t measure”.
DJ: What is the next application with the research?
Marrone: This research was done using one species of algae. There are many more that are being pursued for biofuels and bioproducts development. We aim to demonstrate the utility of our methods by using them to measure and select for certain phenotypes in other algae species.
