Andersson L, Yang S, Neubauer P, Enfors S O
Department of Biochemistry and Biotechnology, Royal Institute of Technology (KTH), Stockholm, Sweden.
J Biotechnol. 1996 May 15;46(3):255-63. doi: 10.1016/0168-1656(96)00004-1.
Fed batch cultivations of plasmid-free and recombinant Escherichia coli were employed in order to determine cellular responses and effects of plasmid presence and induction on the host cell physiology. While plasmid presence was shown to have minor influence on overall biomass yield, induction with 0.1 mM IPTG led to a marked reduction. The number of dividing cells, measured as colony forming ability, was influenced by plasmid presence and to a larger extent by induction. The latter caused a decline in the number of dividing cells to less than 10% of the population within 10 h. However, this cell segregation did not affect the specific rate of product formation, which was approximately constant throughout the cultivations. Analysis of the in vivo degradation rate of the product indicated that it was proteolytically stable. The cellular content of the stringent response signal substance, ppGpp, peaked immediately after transition from batch to fed batch mode to stabilise at a higher value than in the batch phase. When the specific growth rate declined below 0.06 h-1 an additional rise in ppGpp concentration was observed.
为了确定无质粒和重组大肠杆菌的细胞反应以及质粒的存在和诱导对宿主细胞生理学的影响，进行了补料分批培养。虽然质粒的存在对总生物量产量影响较小，但用0.1 mM异丙基-β-D-硫代半乳糖苷（IPTG）诱导导致显著降低。以菌落形成能力衡量的分裂细胞数量受质粒存在的影响，并且在更大程度上受诱导的影响。后者导致分裂细胞数量在10小时内降至不到群体的10%。然而，这种细胞分离并不影响产物形成的比速率，在整个培养过程中该比速率大致恒定。对产物体内降解速率的分析表明它在蛋白水解方面是稳定的。严格反应信号物质鸟苷四磷酸（ppGpp）的细胞含量在从分批培养模式转变为补料分批培养模式后立即达到峰值，并稳定在高于分批培养阶段的值。当比生长速率降至低于0.06 h-1时，观察到ppGpp浓度进一步升高。
