Abstract
Yeast has been engineered for
cost-effective organic acid production through metabolic engineering and
synthetic biology techniques. However, cell growth assays in these
processes were performed in bulk at the population level, thus obscuring
the dynamics of rare single cells exhibiting beneficial traits. Here, we
introduce the use of monodisperse picolitre droplets as bioreactors to
cultivate yeast at the single-cell level. We investigated the effect of
acid stress on growth and the effect of potassium ions on propionic acid
tolerance for single yeast cells
of different species, genotypes
and phenotypes. The results showed that
the average growth of single yeast
cells in microdroplets was identical to those of yeast populations grown
in bulk, and microdroplet compartments do not significantly affect cell
viability. This approach offers the prospect of detecting cell-to-cell
variations in growth and physiology and is expected to be applied for
the engineering of yeast to produce value-added bioproducts.