Ultra-High-Throughput Screening of Enzyme Libraries with Droplet-Based Microfluidics

Directed evolution relies on the ability to screen large, diverse libraries of sequence variants. We have developed a microfluidic platform for ultra-highthroughput screening of enzyme libraries. Individual enzyme variants are assayed in a monodisperse water-in-oil microemulsion. Aqueous droplets compartmentalize the enzymatic reaction and maintain the genotype-phenotype linkage. A quantitative fluorescence detection system allows droplets to be analyzed and sorted at rates beyond 1 kHz. This screening platform provides a throughput that is orders of magnitude beyond traditional plate-based screens.