Synthetic cellular communication-based screening for strains with improved 3-hydroxypropionic acid secretion

Although cellular secretion is important in industrial biotechnology, its assessment is difficult due to the lack of efficient analytical methods. This study describes a synthetic cellular communication-based microfluidic platform for screening strains with the improved secretion of 3-hydroxypropionic acid (3-HP), an industry-relevant platform chemical. 3-HP-secreting cells were compartmentalized in droplets, with receiving cells equipped with a genetic circuit that converts the 3-HP secretion level into an easily detectable signal. This platform was applied to identify Escherichia coli genes that enhance the secretion of 3-HP. As a result, two genes (setA, encoding a sugar exporter, and yjcO, encoding a Sel1 repeat-containing protein) found by this platform enhance the secretion of 3-HP and its production. Given the increasing design capability for chemical-detecting cells, this platform has considerable potential in identifying efflux pumps for not only 3-HP but also many important chemicals.