Recombinant E. coli strains and culture conditions were studied for the fermentation expression of porcine somatotropin (PST) inclusion bodies under the control of a pL promoter. Our objective was to achieve high cell density together with a high level of recombinant protein expression. Improved fermentation conditions included oxygen enrichment, yeast extract (YE) effect, optimal specific growth to switch on gene expression, and feeding strategies. To maintain a low residual glucose concentration, a medium feed rate was controlled on a real-time basis by using cell density information estimated from on-line carbon dioxide monitoring of a fermentor's exhaust gas. The optimal specific growth rate required to initiate a temperature shift in our system was found to be around 0.2 hr-1. The cell density and PST expression level could reach 55 OD600 and 35%, respectively, after 16 hours of cultivation under optimal conditions by applying computer-controlled nutrient feed. In our recombinant host/vector system, the location of cl gene appears to affect gene expression under YE-supplemented and/or a high cell density culture condition. With cl gene placed on plasmid, our E. coli host no longer showed sensitivity toward YE in PST gene expression.
[1]
J. Neway,et al.
Effects of medium quality on the expression of human interleukin-2 at high cell density in fermentor cultures of Escherichia coli K-12
,
1990,
Applied and environmental microbiology.
[2]
T. Ritch,et al.
Production of human alpha consensus interferon in recombinant Escherichia coli
,
1986
.
[3]
S. Shimizu,et al.
High Concentration Cultivation of Candida brassicae in a Fed-Batch System
,
1985
.
[4]
C L Cooney,et al.
Growth monitoring and control in complex medium: A case study employing fed‐batch penicillin fermentation and computer‐aided on‐line mass balancing
,
1983,
Biotechnology and bioengineering.
[5]
Henry Y. Wang,et al.
Computer‐aided baker's yeast fermentations
,
1977,
Biotechnology and bioengineering.