title: High-Throughput Accurate Single-Cell Screening of Euglena gracilis with Fluorescence-Assisted Optofluidic Time-Stretch Microscopy.
abstract: The development of reliable, sustainable, and economical sources of alternative fuels is an important, but challenging goal for the world. As an alternative to liquid fossil fuels, algal biofuel is expected to play a key role in alleviating global warming since algae absorb atmospheric CO2 via photosynthesis. Among various algae for fuel production, Euglena gracilis is an attractive microalgal species as it is known to produce wax ester (good for biodiesel and aviation fuel) within lipid droplets. To date, while there exist many techniques for inducing microalgal cells to produce and accumulate lipid with high efficiency, few analytical methods are available for characterizing a population of such lipid-accumulated microalgae including E. gracilis with high throughout, high accuracy, and single-cell resolution simultaneously. Here we demonstrate high-throughput, high-accuracy, single-cell screening of E. gracilis with fluorescence-assisted optofluidic time-stretch microscopy-a method that combines the strengths of microfluidic cell focusing, optical time-stretch microscopy, and fluorescence detection used in conventional flow cytometry. Specifically, our fluorescence-assisted optofluidic time-stretch microscope consists of an optical time-stretch microscope and a fluorescence analyzer on top of a hydrodynamically focusing microfluidic device and can detect fluorescence from every E. gracilis cell in a population and simultaneously obtain its image with a high throughput of 10,000 cells/s. With the multi-dimensional information acquired by the system, we classify nitrogen-sufficient (ordinary) and nitrogen-deficient (lipid-accumulated) E. gracilis cells with a low false positive rate of 1.0%. This method holds promise for evaluating cultivation techniques and selective breeding for microalgae-based biofuel production.
authors.affiliation: Department of Chemistry, University of Tokyo, Tokyo 113-0033, Japan.
authors.forename: Baoshan
authors.initials: B
authors.lastname: Guo
authors.affiliation: Department of Chemistry, University of Tokyo, Tokyo 113-0033, Japan.|Department of Electronic Engineering, Tsinghua University, Beijing 100084, China.
authors.forename: Cheng
authors.initials: C
authors.lastname: Lei
authors.affiliation: Japan Science and Technology Agency, Kawaguchi 332-0012, Japan.
authors.forename: Takuro
authors.initials: T
authors.lastname: Ito
authors.affiliation: Department of Chemistry, University of Tokyo, Tokyo 113-0033, Japan.
authors.forename: Yiyue
authors.initials: Y
authors.lastname: Jiang
authors.affiliation: Department of Electrical Engineering and Information Systems, University of Tokyo, Tokyo 113-8656, Japan.
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Ozeki
authors.affiliation: Department of Chemistry, University of Tokyo, Tokyo 113-0033, Japan.|Japan Science and Technology Agency, Kawaguchi 332-0012, Japan.|Department of Electrical Engineering, University of California Los Angeles, Los Angeles, California, 90095, United States of America.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Goda
mesh_terms: D056804:Biofuels; D005056:Euglena gracilis / Q000737:chemistry / Q000378:metabolism; D057166:High-Throughput Screening Assays / Q000379:methods*; D056656:Lab-On-A-Chip Devices; D050356:Lipid Metabolism; D008055:Lipids / Q000737:chemistry* / Q000302:isolation & purification; D008856:Microscopy, Fluorescence; D059010:Single-Cell Analysis
chemical_list: D056804:Biofuels; D008055:Lipids