Bacteriophages (phages) are present almost everywhere around us. Their key role is regulating microbial community in various ecosystems, therefore they are regaining attention as natural antimicrobial agents for potential antibacterial treatments also in human medicine, especially for multi-drug resistant bacteria. Phages are bacterial viruses which are formed during the process of infection and final lysis of bacteria. In medical applications and therapeutics, large amount and higher concentrations of phages are required. Phages are nowadays still being amplified traditionally, on laboratory scale in shaking culture flasks and as batch process in bioreactors on industry level. In our case, we studied the effect of dilution rate on productivity of continuous production of phages in “cellstat” which consists of two connected glass bioreactors »C« and »P« (volume of the first bioreactor was 25 mL and second bioreactor was 5 mL, respectively), run by a single pump. Fresh LB medium was continuously pumped in the first bioreactor »C« where bacteria were continuously growing and then continuously introduced into second bioreactor »P« where multiplication of phages occurred. As a model system we used well-studied phage T4 and Escherichia coli K-12 as a host. Two different sets of experiments where bacterial physiological state was either varied or kept constant were performed. When the steady state was reached, concentration of phages at the outflow of second bioreactor was evaluated by standard plaque assay and average values were obtained. Productivity of continuous production of bacteriophages was calculated from average phage titers and dilution rate in second bioreactor. The results obtained show that there exists an optimal dilution rate when maximal phage concentration and productivity are achieved.
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