Variable-volume chemostat and applications thereof

A chemostat, comprising:

• a bioreactor chamber containing media with cells for cell growth and cell division;
• an input tube coupled to the chamber for delivering nutrient-laden media that support the cell growth and the cell division within the chamber, at an inflow rate;
• and
• an output tube coupled to the chamber for withdrawing a sample from the chamber at an outflow rate,
• wherein the inflow rate and the outflow rate are regulated such that the chemostat is operable in a sample accumulation phase or a sample withdrawal phase immediately following the sample accumulation phase, wherein in the sample accumulation phase, the outflow rate is zero and the inflow rate increases in proportion to an instantaneous volume of media in the chamber so as to accumulate the sample without changes in a metabolic state within the chamber;
• and wherein in the sample withdrawal phase, the outflow rate is regulated at a higher rate than the inflow rate to withdraw the accumulated sample from the chamber rapidly at one time and the inflow rate remains in proportion to the instantaneous volume to maintain chemostasis in the chamber.