Abstract: The gene encoding of Brazzein was modified according to the codon bios in Lactococcus lactis and three sense mutations in Brazzein, Asp29Lys, His31Ala, Glu41Lys were generated in an attempt to enhance the sweetness.The optimized gene was amplified by overlap PCR and the fragment was subcloned into pMD18-T vector, followed by being sequenced.The gene of interest was cloned into pNZ8112 expression vector and recombinant plasmid was transformed intoL. lactis by electroporation to construct the surface display system for expression of the Brazzein protein on the surface of L. lactis.

Key words: sweet protein, Brazzein, Lactococcus lactis, surface display