Abstract
Background: Growing worldwide problem of antibiotic resistance has made infection with drug-resistant bacteria, such as Acinetobacter baumannii, an acute public health issue. As a result, development of novel and efficient treatment strategies is presently required. This study employed a Plackett–Burman design (PB) to identify the key auto-induction medium components affecting recombinant endolysin production in Escherichia coli BL21 (DE3) and its lytic activity against antibiotic-resistant A. baumannii strains. Methods: Five parameters were screened using a 12 run PB design: concentrations of glucose, glycerol, MgSO4.7H2O, lactose, and lactose addition time. The recombinant endolysin extracted from the E. coli cells in each run and its activity was determined by turbidity reduction assay against an antibiotic-resistant A. baumannii strain. Results: Analysis of Variance (ANOVA) revealed that glucose, glycerol, and lactose significantly influenced recombinant endolysin production and lytic activity (p-value < 0.05), whereas MgSO4.7H2O and lactose addition time showed no significant effect. The results reflect screening-level functional activity rather than quantitative protein expression. The Plackett–Burman screening identified glucose, glycerol, and lactose as the significant factors influencing endolysin activity. A linear correlation was observed between increased glycerol and lactose concentrations and higher endolysin activity, while glucose exerted its effect within a narrow range. The condition corresponding to the highest activity within the tested PB matrix was observed at low glucose (0.0247% w/v), high glycerol (5.92% w/v), and high lactose (4.880% w/v). Conclusion: These findings highlight the key factors influencing endolysin production and provide a basis for subsequent detailed optimization studies.