Construction of various bacteriophage λ mutants for stable and efficient production of recombinant protein in Escherichia coli

Using the rate of respiration to monitor events in the infection of Escherichia coli cultures by bacteriophage T4

The growing interest in applications of bacteriophages creates a need for improvements in the production processes. Continuous monitoring of the phage production is an essential aspect of any control strategy and, at present, there is no completely satisfactory option. The approach presented here uses IR-spectrometry to continuously measure the rate of respiration (CO(2) released) of Escherichia coli infected by phage T4 at various multiplicities of infection (MOI). Within the trends in these data, or in other aspects of the rate of respiration, it was possible to reliably and reproducibly identify five features that reflected specific events in the infection process. These included two events in the host cell apparent growth rate and events in the magnitude of the host cell density, in the measurement of OD(600) or in the specific rate of respiration. All of these correlations were within 95% confidence showing that they are suitable for the monitoring and control of E. coli populations infected by phage T4. This method is reliable, cheap, and can be operated in-line and in real time.

Enhancement of bacteriophage λ stability using a λQ-S- mutant in the continuous culture of Escherichia coli

In this study, we used a bacteriophage λQ⁻S⁻ mutant that increased the stability of recombinant Escherichia coli during continuous culture. The operation was conducted in two stages: the first stage was carried out to promote cell growth, and the second stage was performed for product formation. The productivity of recombinant proteins depends on the substrate concentration of the fresh medium supplied to the second stage (S₃) and dilution rate of the second stage (D₂). With the optimal value of S₃ and D₂, the first and second stages were stably maintained for 170 and 80 h, respectively. To further improve this process, a three-stage continuous process was conducted with an additional induction stage between the growth and production stages. Compared with the two-stage operation, the stable production period was extended by 1.7 fold, and the recombinant protein production increased by 1.3 fold.