Fig. 4

Development of fluorescence signal in dependency to pH changes in cultures of E. coli BL21 and E. coli MG1655 confined in microfluidic droplets without pH regulation. Droplet populations were incubated in customized incubators as part of the dynamic droplet incubation setup, with which oxygen was continuously supplied. The incubators were equipped with an excitation light source and a fiber guide leading to a photodiode. a Course of fluorescence intensity during microbial incubation in droplets for the replicate droplet cultivations with strains E. coli BL21 and E. coli MG1655. Fluorescence intensity was determined for entire droplet populations in the incubator. Rx indicates a different biological replicate from which the data was collected. b Representative images of droplets and offline parameters recorded for E. coli fermentation in pL droplets. Optical cell density (OD₆₀₀), concentration of glucose and pH with standard pH electrode were measured before or after the incubation in droplets in the aqueous phase. Droplets were fused after incubation by using an anti-static gun [14]