Secretory expression of lacticin Q fused with SUMO in Bacillus subtilis

Lacticin Q is a 53-amino acid Class II bacteriocin produced by Lactococcus lactis QU 5. It shows antibacterial activity comparable to that of nisin A in terms of both spectrum and intensity. Moreover, it remains stable at alkaline pH values, while nisin A was inactivated. It may possibly be employed as an alternative to or in combination with nisin A. The objective of this study was to express lacticin Q extracellularly with Small ubiquitin-related modifier (SUMO) fusion technology in Bacillus subtilis. Secretory SUMO-lacticin Q fusion protein was efficiently produced in B. subtilis WB600 transformed with the recombinant expression plasmid and accounted for 19% of the culture supernatant proteins. Fusion SUMO-lacticin Q was purified by nickel nitrilotriacetate (Ni–NTA) affinity chromatography and digested with SUMO protease to release lacticin Q. Lacticin Q was further purified by Ni–NTA chromatography to yield about 2.5 mg of lacticin Q with more than 93% purity from 1 L of supernatant of fermentation culture. An activity assay indicated that the recombinant bacteriocin exhibited excellent antimicrobial activity against indicator strains. The results obtained suggest that the secretory lacticin Q was efficiently expressed using SUMO fusion technology in B. subtilis. The expression and purification system could promote the application of lacticin Q in food and medicine.

► Secretory expression of lacticin Q fused with SUMO in Bacillus subtilis was performed. ► The purification process of lacticin Q is improved. ► The recombinant lacticin Q is active against indicator strains. ► The expression procedures could promote the use of lacticin Q.