Abstract:
:Plasmid instability of a recombinant Saccharomyces cerevisiae C468/pGAC9 (ATCC 20690) was examined during continuous culture in a nonselective medium in an airlift bioreactor. The recombinant strain contained a 2-micron based shuttle vector pGAC9 and expresses Aspergillus awatnori glucoamylase gene under the control of the yeast enolase I (ENO1) promoter. The changes in the fraction of plasmid-bearing cells and glucoamylase activity followed first-order kinetics. Expressed as a function of time, the decay rates of both the plasmid-bearing cell fraction and glucoamylase expression increased with increasing dilution rates. If expressed as a function of cell generations, the decay rates were nearly constant over the dilution rates tested. The results indicated that the growth rate difference between plasmid-bearing and plasmid-free cells was negligible. This was probably due to the low copy number of the 2-micron based yeast shuttle vector. Thus the contribution of preferential growth to apparent plasmid instability was negligible. A novel numerical method is proposed to evaluate the parameters related to plasmid stability. The estimated values of probability of plasmid loss (P = 0.0499) were nearly constant at different dilution rates. No significant effect of growth rates on plasmid instability was observed. The proposed kinetics agreed well with experimental observations.
journal_name
J Biotechnoljournal_title
Journal of biotechnologyauthors
Zhang Z,Scharer JM,Moo-Young Mdoi
10.1016/s0168-1656(97)00057-6subject
Has Abstractpub_date
1997-05-23 00:00:00pages
31-41issue
1eissn
0168-1656issn
1873-4863pii
S0168-1656(97)00057-6journal_volume
55pub_type
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journal_title:Journal of biotechnology
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