Storage stability of food-grade recombinant Lactococcus lactis NZ3900-fermented milk expressing K-ras mimotopes

K-ras mimotope expressed by Lactococcus lactis NZ3900 is a potential live oral vaccine developed to target specific K-ras mutations in colorectal cancer. However, the storage and delivery of live oral vaccines through the harsh gastrointestinal environment remains a challenge. Hence, this study was aimed to evaluate the storage stability of Lactococcus lactis NZ3900 expressing K-ras mimotopes in fermented milk. The L. lactis NZ3900 expressing K-ras mimotopes was incorporated into skim milk for fermentation. The L. lactis-fermented milk was added with sucrose and stored for 42 days at 4 °C. The L. lactis NZ3900-fermented milk without sucrose was served as control. On day 28 of storage, L. lactis NZ3900-fermented milk with sucrose displayed high viability (8.05 log₁₀ CFU/mL), acceptable post-acidification activity (0.91% titratable acidity, pH 4.11), comparable physicochemical properties (13,949 mPa s viscosity, 71.4% syneresis, 5.83°Brix, \(\Delta\) $\mathrm{\Delta }$ E = 1.68) with K-ras mimotope expression, and high survivability after simulated sequential digestion (82.5%). This suggests that fermented milk with sucrose is a suitable delivery carrier for this live oral vaccine.