Constitutive production of the receptor-binding domain of the F18 fimbriae on the surface of <Emphasis Type="Italic">Lactococcus lactis</Emphasis> using synthetic promoters

Nine synthetic constitutive promoters with different activities were produced for the surface display of the receptor-binding domain of the F18 fimbrial adhesin FedF in Lactococcus lactis. The promoters were synthesized from an oligonucleotide, designed to allow for randomization of bases between defined lactococcal promoter consensus regions. However, promoters with spontaneous modifications were selected for fedF expression, indicating that the consensus promoter was too strong. The amount of FedF on the surface of the best performing promoter clone was comparable to the amount of FedF produced by a L. lactis strain with an optimized NICE expression system. Stability of FedF production further suggested that an optimal constitutive expression level was attained.