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  • 1
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Functional bivalent miniantibodies, directed against the epidermal growth factor receptor, accumulated to more than 3 gl−1 in high-cell-density cultures of Escherichia coli RV308(pHKK) on a pilot scale. The miniantibodies consist of scFv fragments with a C-termi-nal hinge followed by a helix-turn-helix motif, which homodimerizes in vivo. The improved expression vector pHKK is characterized by the hok/sok suicide system, improving plasmid maintenance, and the inducible lac p/o promoter system with the very strong T7g10 Shine-Dalgarno sequence. The expression unit is flanked by terminators. The prototrophic RV308 cells were cultivated in glucose mineral salt medium and reached a cell density of 145 g dry biomass l−1 after 33 h. After induction, growth continued almost unchanged for a further 4 h with concomitant miniantibody formation. In the fed-batch phase, the concentration of glucose was kept almost constant at the physiological level of approximately 1.5 g l−1, using on-line flow injection analysis for control. Surprisingly, E. coli RV308(pHKK) did not accumulate significant amounts of the metabolic by-product acetate under these unlimited aerobic growth conditions.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The paper describes the synthesis of the phosphorylcholine-binding miniantibody McPC603scFvDhl x in cell-wall-less L-form strains of Escherichia coli and Proteus mirabilis. Cells of these strains were transformed with the plasmid pACK02scKan, carrying the miniantibody (miniAb) coding sequence under the control of the lac promoter. L-form transformants of both species were able to synthesize the functional miniAb as an extracellular soluble product. The highest quantities were obtained by P. mirabilis L-form strains after induction with 5 mM isopropyl β-d-thiogalactopyranoside (IPTG). Yields of 45–75 mg/l total antibody protein and of 10–18 mg/l functional miniAb were estimated in the growth medium of shaking cultures 40–80 h after induction with IPTG. About 10% of the active miniAb remained cell-bound. The yields of functional miniAb could be optimized by lowering the growth temperature from 37 °C to 26–32 °C and by supplementation of the medium with 80 mM sodium fumarate. A comparison of the specific activities revealed that the P. mirabilis L-form strains have a similar synthesis capacity (2–4 mg functional miniAb/g cell dry weight) to that of the producer strain E. coli RV308. The results show that the processes of correct folding and assembling of the miniAb molecules are possible without the periplasmic compartment.
    Type of Medium: Electronic Resource
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