Effect of dilution rate on the metabolism and product formation of a recombinant mammalian cell line growing in a chemostat with internal recycle of cells
A recombinant CHO cell line capable of high level expression of a heterologous protein, human growth hormone, was grown attached to microcarriers. Growth and product formation by the cell line was studied in a continuous culture system with internal recycle of the cells. The culture was fed at dilution rates from 0.03 to 0.19 h-t with a protein free defined medium. The attached cell densities, the percentage of confluent microcarriers and the specific hGH productivities were all functions of the dilution rate, the optimum rate being 0.12h-1. At dilution rates lower than 0.12h-1, the metabolic rate of the culture was controlled by the dilution rate. Limitation of glucose or glutamine or end product inhibition by ammonium or lactate were ruled out as possible causes, and it was felt that the supply of amino acids, in particular cystine, serine and aspartic acid was probably limiting metabolism at the low dilution rates.
KeywordsDilution Rate Human Growth Hormone Amino Acid Concentration Spinner Flask Airlift Reactor
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