A Bacterial Continuous Culture System Based on a Microfluidic Droplet Open Reactor

Abstract

Recently, micrometer-sized bacterial culture systems have attracted attention as useful tools for synthetic biology studies. Here, we present the development of a bacterial continuous culture system based on a microdroplet open reactor consisting of two types of water-in-oil microdroplets with diameters of several hundred micrometers. A continuous culture was realized the through supply of nutrient substrates and the removal of waste and excess bacterial cells based on repeated fusion and fission of droplets. The growth dynamics was controlled by the interval of fusion. We constructed a microfluidic system and quantitatively assessed the dynamics of the bacterial growth using a mathematical model. This system will facilitate the study of synthetic biology and metabolic engineering in the future.

In vivo, in vitro and in silico: an open space for the development of microbe‐based applications of synthetic biology

“…Yet, because these vessels are at least a few millilitres in volume, this setting precludes carrying out large‐scale experiments with many vessels working in parallel. This drawback triggered the development of continuous culture systems based on open reactors managing microfluidic droplets [see (Ito et al ., 2016) and the special issue on recent advances of molecular machines and molecular robots edited by Takinoue and Kawano, which describes advances in the domain, mainly in Japan (Takinoue and Kawano, 2020)]. The future of laboratory‐set evolution is now likely to rest on nanolitre reactors such as those already used for production of important metabolites (Xu et al ., 2020), allowing in vivo directed evolution (Femmer et al ., 2020).…”

Recent advances of integrated microfluidic suspension cell culture system

“…It is important to perform several culture protocols (e.g. growth media refreshment, metabolites removal and reagent addition into droplets) for controllable growth dynamics [124], long-term continuous culture [69,125], adaptive evolution research [126] and cell-based screening [42]for synthetic biology. These operations are generally executed in water-in-oil droplets for regulating the dynamic culture environment, which can be achieved through the interplay between microchannel geometries, microvalve and electrodes, such as pico-injection, splitting and fusion [34,42,111,125].…”

Fabrication of Circular Cross-Section Microchannels with 3-D Lattice Arrangement and Their Use as On-Off Valves

“…In the research on synthetic biology, precise control of the amount of chemicals in small reactors is required by adjusting the feed amount of chemicals with a nanolitre scale over a long period of time [2]. Microchannels with an on-off valve function have been proposed as a device to precisely control the amount of chemicals to be mixed [3,4].…”