In this study, bacteriocin‐producing Lactococcus lactis subsp. lactis GYL32 strain was isolated from Boza. The GYL32 strain inhibited not only related strains but also gram‐positive bacteria, such as Listeria monocytogenes, Staphylococcus aureus and Bacillus cereus. The antimicrobial substance was inactivated after treatment with proteinase K and α‐chymotrypsin but not other enzymes. Bacteriocin remained active after 2 h of incubation at pH 2–11. It was stable to heat after treatment at 100C for 20 min. The bacteriocin produced by GYL32 was characterized as nisin by different pH, enzyme and heat treatments. The sequence analysis result showed that it is nisin Z, and its genetic determinants are encoded on genomic DNA. The maximum antimicrobial activity (5,120 AU/mL) was recorded after 8 h in M17 broth. Tricine‐SDS‐PAGE analysis showed that its molecular weight 6,700 Da. L. lactis subsp. lactis GYL32 strain may be used as a protective culture for manufacturing fermented products. Practical Applications Nisin is the best‐studied bacteriocin produced by some Lactococcus lactis strains and has been used for food preservation in over 50 countries. The present study describes isolation and characterization of nisin Z‐producing L. lactis strain isolated from traditional cereal‐based fermented food, which is Boza from Turkey. The results of this study suggest that nisin Z producer L. lactis subsp. lactis GYL32 strain may be used as a starter culture for improving the food safety of the fermented products.