Expression of bovine trypsin in Lactococcus lactis

Bovine trypsin is widely used in the production of bioactive peptides from milk proteins. The objective of this study was to express bovine trypsin in Lactococcus lactis to produce peptides by fermentation. The bovine trypsin with bias codon of L. lactis was synthesized, cloned into a secretory expressive vector pSEC-E7, and then introduced to L. lactis strain NZ9000 by electroporation. The expression of trypsin induced by nisin was identified by Western blot. Western blot analysis revealed a band in the protoplast fraction corresponding to SPUsp45 (signal peptide of usp45)-trypsin. Biological activity of expressed trypsin was confirmed by the single substrate overlay assay. These results suggest that the expression of biologically active bovine trypsin has been detected in the protoplast fraction of L. lactis strain NZ9000 (pSEC:trypsin).