Kinetics of continuous GM-CSF production by recombinant Saccharomyces cerevisiae in an airlift bioreactor

被引:9
作者
Shu, CH [1 ]
Yang, ST [1 ]
机构
[1] OHIO STATE UNIV,DEPT CHEM ENGN,COLUMBUS,OH 43210
关键词
Saccharomyces cerevisiae; GM-CSF; kinetics; air-lift bioreactor;
D O I
10.1016/0168-1656(96)01409-5
中图分类号
Q81 [生物工程学(生物技术)]; Q93 [微生物学];
学科分类号
071005 ; 0836 ; 090102 ; 100705 ;
摘要
Continuous production of murine GM-CSF by recombinant Saccharomyces cerevisiae in an airlift bioreactor was studied at three different dilution rates. The reactor was initially fed with a selective medium to increase cell concentration, and then was fed with a rich, nonselective medium for GM-CSF production. Ethanol was used as the main carbon source to provoke GM-CSF expression. In continuous culture, GM-CSF production was maintained for over 150 h, even though the fraction of plasmid-carrying cells continuously dropped to lower than 20%. The stable GM-CSF production during the later phase of the continuous culture was attributed to increased specific cell productivity possibly resulting from an increase in the plasmid copy number in plasmid-carrying cells. This also indicated the possibility of natural selection of high-copy number cells in continuous culture. Plasmid stability was found to be growth rate (dilution rate) dependent; it increased with the dilution rate. Reactor productivity and specific productivity also increased with the dilution rate. A two-parameter kinetic equation was used to model the plasmid stability kinetics. The growth rate ratio between plasmid-carrying and plasmid-free cells increased from 0.996 to 0.998 while the segregational instability or the probability of plasmid loss from each cell division increased from 1.1% to 16% as the dilution rate decreased from 0.11 h(-1) to 0.05 h(-1). Oscillation of the dilution rate between 0.05 h(-1) and 0.11 h(-1) stabilized the plasmids and gave a higher productivity than that achieved without oscillation.
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页码:107 / 116
页数:10
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