1Department of Genetics, Universidad de Sevilla, Seville, Spain
2Ingeniatrics Tecnologías SL, Spain
3Department of Microbiology and Parasitology, Universidad de Sevilla, Seville, Spain
4Centro Andaluz de Biología del Desarrollo, Universidad Pablo de Olavide, Seville, Spain
5Biomedal SL, Spain
Characterization of microorganisms usually involves culture during more than 20 generations in order to achieve the formation of macrocolonies on solid media. Alternatively, microencapsulation allows the detection of microbial growth by monitoring the development of microcolonies from encapsulated individual cells. Microbial proliferation inside the microcapsules can be detected using flow cytometry, provided that the population of microparticles exhibits appropriate optical and mechanical properties and is monodisperse in size and shape.
Using a Cellena® Flow Focusing® microencapsulator (Figures 1 and 2), we managed to produce monodisperse alginate microparticles containing individual bacteria, yeast and human stem cells (Figure 3). Alginate particle sizes were reproducibly selected from less than 100 µm to over 600 µm, by replacing the disposable nozzle. Sterility was preserved during the microencapsulation procedure, preventing undesired contaminations.Microencapsulated microorganisms were used for a variety of application: from characterizing secreted enzymes to detection of thermosensitive mutants. Proliferation inside the particles was monitored by flow cytometry without requiring fluorescent labelling.