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bioreactor studies of heterologous protein production by ...

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Bentley and Kompala, 1989; Satyagal and Agrawal, 1989). Inmashg <strong>protein</strong> yidd<br />

accompanied <strong>by</strong> decreasing specinc growth rate is possibIy due to incnasing the copy<br />

number, even though the copy number was not measured in this work. If the copy number<br />

was the same regardles <strong>of</strong> the specific growth rate. increaSing <strong>protein</strong> yiehi would be due<br />

to an inmase in DNA transcription efficiency as a consequence <strong>of</strong> the increase in the<br />

inûaœilular promoter concentration (Hardjito et ai.. 1992). The upedmental findings <strong>of</strong><br />

Park and Ryu (1990) supported this assumption. In a two-stage continuous system with a<br />

recombinant E. coli K12AHIdoplpPLc23npk they iavestigated the effm <strong>of</strong> dilution rate<br />

on Trpa <strong>production</strong>. The plasrnid content (mg DNA per mg cells) was found to be<br />

practically the same independent <strong>of</strong> the dilution rate; however the <strong>protein</strong> yield (units <strong>of</strong><br />

<strong>protein</strong> per mg ce&) decreased as dilution rate increased. In other words, the<br />

transcription efficency decreased with increashg dilution rate.

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