Table 1.

Strains and plasmids used in this study

Strain or plasmidDescriptionReference or source
Strains
L. helveticus53/7Industrial starter strainValio Ltd.
L. lactissubsp. cremoris
  MG1363Plasmid-free derivative of NCDO71210
  MG1363[XTOCN] ΔpepXΔpepT ΔpepO ΔpepCΔpepN 19
  MG1363[NC] ΔpepNΔpepC 19
  MG1363 (Prt+Lac+)pLP71210
  MG1363[XTOCN](Prt+ Lac+)ΔpepXΔpepT ΔpepO ΔpepCΔpepN (pLP712)19
  MG1363[X]− (Prt+ Lac+)ΔpepX(pLP712)16
  MG1363[N]− (Prt+Lac+)ΔpepN (pLP712)10
L. lactis NZ9000 nisR + nisK + NIZOa
E. coli DH5αF80 lacZDM15 Δ(lacZYA-argF) U169 recA1 endA1 hsdR17 supE44 thi-1 gyrA96 relA1 12
Plasmids
 pKTH2095Emr; 4.5 kb; pGK12 with pUC19 multilinker, pWV01 replicon13
 pIL277Emr; 4.3 kb; pAMβ1 replicon24
 pNZ8037Cmr; 3.1 kb; pSH71 replicon,PnisA 5
 pKTH2073pUC19 with L. helveticus pepN as 3.7-kb XbaI insert26
 pKTH2097pJDC9 with L. helveticus pepX in 2.6-kb BamHI insert31
 pKTH2105pJDC9 withL. helveticus pepD as 1.6-kbBamHI-SalI insert30
 pKTH2082pJDC9 with L. helveticus pepR as 1.1-kbBamHI-SalI insert27
 pKTH2172 L. helveticus pepN in pKTH2095 under control of its own promoterThis work
 pKTH2171 L. helveticus pepX in pKTH2095 under control of its own promoterThis work
 pKTH2175 L. helveticus pepC in pIL277 under control of its own promoterThis work
 pKTH2179 L. helveticus pepI in pKTH2095 under control of PpepX This work
 pKTH2150 L. helveticus pepD in pKTH2095 under control of its own promoterThis work
 pKTH2170 L. helveticus pepR in pKTH2095 under control of its own promoterThis work
 pKTH2182 L. helveticus pepD in pNZ8037 under control of PnisA This work
 pKTH2193 L. helveticus pepR in pNZ8037 under control of PnisA This work
  • a NIZO, Ede, The Netherlands.