Integrated Microbioreactor for Culture and Analysis of Bacteria, Algae and Yeast

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Integrated Microbioreactor for Culture and Analysis of Bacteria, Algae and Yeast

Sam H. Au1, Steve C.C. Shih1 and Aaron R. Wheeler1,2
Institute of Biomaterials and Biomedical Engineering1 and Department of Chemistry2
University of Toronto, Canada

Microorganisms such as bacteria, algae, and yeast are important tools used in a wide range of applications. Microorganisms are typically grown in volumes of hundreds of microliters to thousands of liters in specialized growth media, often accompanied by active mixing and temperature control. A common method for monitoring microorganism cell growth is by measuring the absorbance of light as it passes through culture fluid. As biomass accumulates, the amount of light absorbed increases in a predictable manner, often reported as optical density. Many applications using microbes require large quantities of consumables, numerous replicates and/or tedious manual operation. There is therefore great interest in developing miniaturized analogues to reduce the costs of consumables, increase throughput and reduce manual labour requirements. Most efforts in miniaturizating microbioreactors have relied on enclosed networks of microchannels which often contain valves, micromechanical mixers and complex optical systems. In contrast, we introduce an automated valve-free, micromixer-free, pump-free microbioreactor relying on digital microfluidics (DMF) that is capable of the growth and density analysis of bacteria, algae and yeast in distinct microdroplets in air. Microorganisms were grown for up to 5 days with automated semi-continuous mixing and temperature control. Cell densities were determined by measuring the absorbance through transparent regions of microbioreactors with a commercially available well plate reader. The growth rates of bacteria, algae, and yeast cultures grown in the DMF system were shown to be very similar to those grown in conventional, macro-scale systems. These results suggest that the new methods have potential for use in miniaturized, automated culture and analysis of microorganisms.