Automatic supplementation of minerals in fed‐batch culture to high cell mass concentration

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Abstract
Automatic constant‐value control of mineral ions was attempted in semibatch culture of high cell mass concentration (more than 150 g dry cell/L) with ethanol and ammonia feeds. Equations were derived from the mass balance principle to calculate the required concentration of each mineral ion in the mineral feed solution, taking into account both the decrease in the volume of the culture supernatant as a proportion of the whole culture broth and the increase in the volume of the whole culture broth during the cultivation. The mineral solution was supplied automatically, linked either with ethanol feed or ammonia water feed. The actual concentrations of mineral ions could be kept within small variations. To adjust the supplementation in accordance with the culture change from oxygen sufficiency (early growth phase) to oxygen deficiency (later growth phase), the concentration of each mineral ion was altered stepwise when the dissolved oxygen concentration fell to zero. The mineral supplementation gave better results coupled with ethanol feed than with ammonia feed. The mineral ions studied were K+, Mg2+, Na+, Fe2+, Zn2+, Ca2+, Co2+, Cu2+, Mn2+, NH+4, PO and SO.