This study describes a controlled gene expression system in Lactococcus lactis using the food-grade inducer nisin. The nisA promoter region was used to create transcriptional and translational fusion vectors for the gusA reporter gene. In the nisin-producing strain NZ9700, β-glucuronidase activity increased rapidly after mid-exponential growth, reaching a maximum at the start of the stationary phase. In non-nisin-producing strains NZ9800 and NZ3900, β-glucuronidase activity was linearly dependent on nisin concentration. A translational fusion vector yielded up to six times more β-glucuronidase activity than a transcriptional fusion vector, allowing gene expression in a dynamic range of over 1,000-fold. The β-glucuronidase activity was 25 times higher in NZ3900 than in NZ9800. This system was used for high-level production of aminopeptidase N, reaching up to 47% of total intracellular protein. The nisin-inducible system offers potential for overproduction of desired proteins in food-grade microorganisms. The system was tested in several lactococcal strains, showing efficient gene expression and regulation. The study highlights the potential of the nisin-inducible expression system for controlled overproduction of proteins in food applications. The system was developed using plasmids with the nisA promoter and various cloning strategies. The results demonstrate the effectiveness of the system for high-level expression of genes in Lactococcus lactis. The system was also used to study the kinetics of nisin induction and to produce aminopeptidase N. The study shows that the nisin-inducible system is a promising tool for controlled gene expression in food-grade microorganisms. The system was developed using plasmids with the nisA promoter and various cloning strategies. The results demonstrate the effectiveness of the system for high-level expression of genes in Lactococcus lactis. The system was also used to study the kinetics of nisin induction and to produce aminopeptidase N. The study shows that the nisin-inducible system is a promising tool for controlled gene expression in food-grade microorganisms.This study describes a controlled gene expression system in Lactococcus lactis using the food-grade inducer nisin. The nisA promoter region was used to create transcriptional and translational fusion vectors for the gusA reporter gene. In the nisin-producing strain NZ9700, β-glucuronidase activity increased rapidly after mid-exponential growth, reaching a maximum at the start of the stationary phase. In non-nisin-producing strains NZ9800 and NZ3900, β-glucuronidase activity was linearly dependent on nisin concentration. A translational fusion vector yielded up to six times more β-glucuronidase activity than a transcriptional fusion vector, allowing gene expression in a dynamic range of over 1,000-fold. The β-glucuronidase activity was 25 times higher in NZ3900 than in NZ9800. This system was used for high-level production of aminopeptidase N, reaching up to 47% of total intracellular protein. The nisin-inducible system offers potential for overproduction of desired proteins in food-grade microorganisms. The system was tested in several lactococcal strains, showing efficient gene expression and regulation. The study highlights the potential of the nisin-inducible expression system for controlled overproduction of proteins in food applications. The system was developed using plasmids with the nisA promoter and various cloning strategies. The results demonstrate the effectiveness of the system for high-level expression of genes in Lactococcus lactis. The system was also used to study the kinetics of nisin induction and to produce aminopeptidase N. The study shows that the nisin-inducible system is a promising tool for controlled gene expression in food-grade microorganisms. The system was developed using plasmids with the nisA promoter and various cloning strategies. The results demonstrate the effectiveness of the system for high-level expression of genes in Lactococcus lactis. The system was also used to study the kinetics of nisin induction and to produce aminopeptidase N. The study shows that the nisin-inducible system is a promising tool for controlled gene expression in food-grade microorganisms.