Abstract
One new strain of Lactobacillus, identified as Lactobacillus rhamnosus TCELL-1, was isolated from the healthy adult rectum biopsies in our laboratory. A new food-grade shuttle cloning vector for Lb. rhamnosus TCELL-1 and E. coli was constructed using the nisin immunity gene nisI as a selection marker. The food-grade shuttle cloning vector, pNI, was constructed using the pAMβ1 replicon, the pUC origin, the nisI gene, the promoter Lac for nisI expression, and the nucT reporter gene. Electroporation into Lb. rhamnosus TCELL-1 was selected with the nucT reporter gene. Plasmid pNI was confirmed in Lb. rhamnosus TCELL-1 with southern hybridization. Lb. rhamnosus TCELL-1 carrying pNI was shown to be able to grow in medium containing a maximum of 60 IU nisin/ml. These results show that the food-grade expression system reported in this paper has potential for expression of foreign genes in Lb. rhamnosus TCELL-1 in order to construct improved starter bacteria for food applications.