High-throughput Microfluidic Screening Platforms for Microalgae Study

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2014-12-15

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Abstract

Microalgae have been envisioned as a future source of renewable energy. Both fossil fuel depletion and environmental concern have drawn more interest in microalgal biofuels, but the production cost of these biofuels are not yet economically competitive. Significant improvements such as development of better performing microalgal strains, optimization of culture conditions, and better understanding of microalgal biology are required for commercial viability. To resolve these limitations, massively parallel studies are needed, however, current microalgae culture systems are lack of high-throughput screening capabilities, and thus not suitable for the parallel studies. Here, three different high-throughput microfluidic microalgae screening platforms have been developed, each of which addresses major bottlenecks towards economically feasible microalgal biofuel.

The first platform, a high-throughput microfluidic photobioreactor array has been developed to investigate the effect of different culture conditions on microalgal growth and oil production. This platform can provide up to 64 different culture conditions on-chip, such as combinations of different light intensities, light cycles, and culture media/chemical compositions. Single cell/colony trapping sites in culture compartments allowed for long-term analysis of microalgal growth and oil production with single cell/colony resolution. The light conditions that induced 1.8-fold higher oil accumulation over the typically used culture conditions were successfully identified.

The second platform, as a microalgae library screening tool, a high-throughput microfluidic single-cell screening and selection platform has been developed to examine growth and oil production of various microalgal strains, followed by selective extraction of particular microalgae showing desired traits to off-chip reservoirs for further analysis. Single microalga was isolated and cultured, and its growth and oil accumulation were analyzed through 1024 single-cell trapping/culturing sites in the platform, where opening and closing of each trap can be individually controlled with integrated microfluidic control layers. By opening only a specific site out of the 1024 trapping sites, microalgae in particular trapping sites were selectively released and successfully collected off-chip.

The third platform, a high-throughput droplet microfluidics-based microalgae screening platform has been developed to investigate the growth and the oil production of microalgal libraries with much higher throughput. Growth was characterized by encapsulating a single microalga into a droplet (functions as an independent bioreactor) and tracking its behavior over time. Oil production was also quantified through on-chip staining process, the key feature of the platform, where oil content in microalgae can be stained and measured through on-chip fluorescent tagging. Growth and oil accumulation under different culture conditions were successfully analyzed and compared, demonstrating the capability of the platform as a high-throughput screening tool.

We have developed series of high-throughput microfluidic screening platforms for microalgae study, which provides the capabilities of analyzing microalgal growth and oil production under different culture conditions or among large numbers of microalgal library. The developed platforms will serve as powerful tools to accelerate research in addressing the limitations of microalgal biofuels as well as to significantly advance the current state of microalgal biofuel production.

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