Droplet-based microfluidic high-throughput screening of heterologous enzymes secreted by the yeast Yarrowia lipolytica.

Droplet-based microfluidics is becoming an increasingly attractive alternative to microtiter plate techniques for enzymatic high-throughput screening (HTS)， especially for exploring large diversities with lower time and cost footprint. In this case， the assayed enzyme has to be accessible to the substrate within the water-in-oil droplet by being ideally extracellular or displayed at the cell surface. However， most of the enzymes screened to date are expressed within the cytoplasm of Escherichia coli cells， which means that a lysis step must take place inside the droplets for enzyme activity to be assayed. Here， we take advantage of the excellent secretion abilities of the yeast Yarrowia lipolytica to describe a highly efficient expression system particularly suitable for the droplet-based microfluidic HTS.