Development of a circulation direct sampling and monitoring system for O2 and CO2 concentrations in the gas–liquid phases of shake-flask systems during microbial cell culture

Schematic flow diagram of the circulation direct monitoring and sampling system for shake-flask (CDMSS). A Culture plug penetrated with a needle; B Erlenmeyer flask with branches on the bottom; C-a the gas circulation system (normal); C-b the gas circulation system (with CO2 absorbent); D the liquid circulation system; 1 connector; 2 0.22 μm filter; 3 flow meter; 4 diaphragm-type pump; 5 liquid measurement unit; 6 gas sampling unit; 7 check valve; 8 column packed with CO2 absorbent; 9 peristaltic pump; 10 liquid measuring unit; 11 liquid sampling uni