Heterologous expression of bovine lactoferrin C-lobe in Bacillus subtilis and comparison of its antibacterial activity with N-lobe

The natural concentration of bovine lactoferrin C-lobe is low and its separation by proteolytic enzyme digestion is difficult. Here, we expressed the codon-optimized fragment of C-lobe on plasmid pMA0911 with the P_veg promoter in Bacillus subtilis 168 at 20 °C. The yield was 7.5 mg/L, and 90.6% purity was achieved using ammonium sulfate precipitation, Ni–NTA and molecular exclusion. The C-lobe at 10 mg/mL completely inhibited cell growth of Escherichia coli JM109 (DE3) and Pseudomonas aeruginosa CGMCC 1.6740, and 48.4% of growth of Staphylococcus aureus CGMCC 1.282, the result is similar to that of 200 ng/mL N-lobe. The minimum inhibitory concentrations of C-lobe were 4, 8 and 16 mg/mL, while those of N-lobe were 128, 256 and 512 μg/mL for E. coli, P. aeruginosa and S. aureus, respectively. This is the first report on bovine lactoferrin C-lobe expression and the comparative resistance of the recombinant N- and C-lobes in a food-safe strain of B. subtilis. Our findings offer the potential to study the structure–function relationship of the N- and C-lobes recombinantly produced in the same host.