Plasmid stability

One of the concerns on plasmid selection for metabolic engineering is plasmid stability problems, which include structural stability and plasmid segregational stability [30]. 

Friehs, K. (2004) Plasmid copy number and plasmid stability. Advances in Biochemical Engineering/Biotech-... 

Several areas are receiving much of the research attention. Approaches that integrate product recovery with the fermentation in a three-phase fluidized bed bioreactor reflect general research trends in biochemical engineering (Yabannavar and Wang, 1991 Davison and Thompson, 1992). The successful use of three-phase biofluidization has also been demonstrated for recombinant protein systems, where it may have some benefit in improving plasmid stability (Shu and Yang, 1996). 

Gerdes, K. (1988). The parB (hoklsok) locus of plasmid Rl a general purpose plasmid stabilization system. Bio/Technology, 6, 1402-5. 

For segregational plasmid stability, cells need to be replicated so that the average number of plasmid copies per cell is doubled once per generation, and the plasmid copies need to be distributed equally to the daughter cells at cell division. It was reported that the problem of plasmid instability was encountered in systems employing E. coll (Kim and Ryu, 1984 Deretic et al., 1984 Caulcott et al., 1985), B. subtilis (Kadam et al., 1987), as well as yeast (Whiteway and Ahmed, 1984 Schwartz et al., 1988) as hosts. 

Parker, C. and D. DiBiasio, "Effect of Growth Rate and Expression Level on Plasmid Stability in Saccharomyces cerevisiae Biotech. Bioeng. 29 (1987) 215-221. 

Mutator plasmid mutation rate of host is enhanced curing strain of plasmid stabilizes the mutation Selifonova, 2001... 

Cochleates can also be used for plasmid delivery. A negatively charged phospholipid such as phosphatidylserine, phosphatidic acid or phosphatidyl glycerol, in the absence or presence of cholesterol, are utilized to produce a suspension of multilamellar vesicles containing plasmids, which are then converted to small unilamellar vesicles by sonication. These vesicles are dialyzed against buffered divalent cations (e.g. calcium chloride) to produce an insoluble precipitate referred to as cochleates. Cochleates have been shown to encapsulate plasmid and enhance plasmid stability and transfection efficiency. 

Yield of IL-4 v Plasmid stability Maintenance of induction capability... 

Vector Remarks strain Plasmid stability Expression level [mg IL-4 g- dry weight] Fermentation yield Expression before induction... 

Fig. 12.1 Plasmid stability of the IL-4 v expression vectors pR021.1.0 (T7-promoter based) and pR02.1.0 (T5 promoter-based). For details, see Table 12.2.

Several samples were taken during the exponential and stationary phases and used for measurement of different parameters such as enzyme yield, cell density, plasmid copy number, and plasmid stability. The optimal enzyme production for all strains was found to be in one of the samples from the stationary growth phase. The obtained maximum cell density varied for the different yeast strains when grown in shake flasks and the enzyme activity data have therefore been corrected for variation in the cell density (Figure 4). The preliminary results from these studies indicate that it is possible to find host systems that are better producers of enzymes than... 

Yu MR, Du YM, Jiang WY, Chang WL, Yang ST, Tang IC. (2012). Effectsof differentreplicons in conjugative plasmids on transformation efficiency, plasmid stability, gene expression and n-butanol biosynthesis in Clostridium tyrobutyricum. Appl Microbiol Biotechnol, 93, 881-889. 

In recombinant microorganisms, plasmid stability is of crucial importance for continued PHB production which is a problem associated with the expression of PHB biosynthetic gene in bacteria... 

In recombinant microorganisms, plasmid stability is of crucial importance for continued PHA production. Some attention has been directed to this problem in recombinant E. coli [154,167]. Another advantage of using E. coli as the production host is the relative ease with which the accumulated PHA can be extracted from the cells [168]. 

A structured, segregated model for genetically modified Escherichia coli cells and its use for prediction plasmid stability. BiotechnoL Bioeng, 36, 581-592. 

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