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  • 1
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A Tn5-based transposon bearing the kil gene (killing protein), mediating controlled export of periplasmic proteins into the culture medium, was constructed (Tn5-KIL3). This transposon contained the kil gene of the ColE1 plasmid under the growth-phase-dependent promoter of the fic gene (filamentation induced by cAMP) of Escherichia coli, an interposon located upstream of kil, a kanamycin/neomycin-resistance gene, a multiple cloning site and the mob site. The transposition of Tn5-KIL3 to Acetobacter methanolicus showed a moderate transposition frequency (10−5–10−6). By insertion of a Bacillus hybrid β-glucanase (bgl ) as a model protein into the transposon (Tn5-LF3) it was shown that the secretion function as well as the gene of the target protein had been transferred to and stably integrated into the chromosome of A. methanolicus, and that the transposition of Tn5-LF3 was non-specific. β-Glucanase was highly overexpressed and secreted into the medium during stationary phase. Total and extracellular production of β-glucanase varied depending on the integration site of the transposon. The viability of the bacterial cells was not affected, and cell lysis did not occur.
    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 Cultivation conditions for the extracellular production of a hybrid β-glucanase from Bacillus were established by using Escherichiacoli JM109 carrying the plasmid pLF3. This plasmid contained a novel secretion system consisting of the kil gene (killing protein) of plasmid ColE1 under the stationary-phase promoter of either the fic or the bolA gene, an omega interposon (Prentki and Krisch 1984) located upstream of the promoters and a hybrid β-glucanase gene of Bacillus. When controlled by the fic promoter, the kil gene led to a higher total production of β-glucanase and a higher protein secretion than when it was under control of the bolA promoter. When the effect of different distances between the stationary-phase promoters and the kil gene was investigated, a shorter distance was generally found to result in a higher secretion. With a complex growth medium, the kinetics of extracellular production of the enzyme depended on several operating variables, such as the salt concentration (NaCl) and the oxygen supply, which were varied by changing the culture volume and the shaking speed. In defined media the secretion of β-glucanase into the medium was increased significantly by the addition of glycerol as a carbon source and by prolonged cultivation. The strain with the highest production and secretion yield of β-glucanase [E. coli JM109(pLF3)] was tested on the fermenter scale.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-072X
    Keywords: Key words Protein secretion ; kil Gene ; β-Glucanase ; Escherichia coli ; Growth-phase-dependent promoter ; Stationary phase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Heterologous gene products produced by Escherichia coli cells can be exported into the culture medium by the action of the kil gene of the ColE1 plasmid, which encodes a bacterial release protein. The kil gene was fused with the stationary-phase promoter of the fic gene of E. coli, and a secretion cassette (Kil-Km cassette) containing the regulated kil gene, the Km-resistance gene, and multiple cloning sites for the integration of target genes was constructed. Using the gene for β-glucanase (bgl) as a target gene, it was shown that the protein produced was only secreted into the medium during the stationary phase. Quasi-lysis and lethality were not observed. The primary effect of the induction of the kil gene was the overproduction of β-glucanase. The total amount produced per milliliter of bacterial culture was almost threefold higher than that of the corresponding Kil– control. The protein pattern of periplasm and culture medium was analyzed before and after induction of the kil gene expression, indicating that the release of periplasmic proteins is semiselective. This secretion system is the first to use a growth-phase-regulated promoter for the expression of the kil gene.
    Type of Medium: Electronic Resource
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