Optimization of Nisin Production by Lactococcus lactis UQ2 Using Supplemented Whey as Alternative Culture Medium

Abstract: Lactococcus lactis UQ2 is a nisin A-producing native strain. In the present study, the production of nisin by L. lactis UQ2 in a bioreactor using supplemented sweet whey (SW) was optimized by a statistical design of experiments and response surface methodology (RSM). In a 1st approach, a fractional factorial design (FFD) of the order 2^5-1 with 3 central points was used. The effect on nisin production of air flow, SW, soybean peptone (SP), MgSO₄/MnSO₄ mixture, and Tween 80 was evaluated. From FFD, the most significant factors affecting nisin production were SP (P = 0.011), and SW (P = 0.037). To find optimum conditions, a central composite design (CCD) with 2 central points was used. Three factors were considered, SW (7 to 10 g/L), SP (7 to10 g/L), and small amounts of added nisin as self-inducer (NI 34.4 to 74.4 IU/L). Nisin production was expressed as international units (IU). From RSM, an optimum nisin activity of 180 IU/mL was predicted at 74.4 IU/L NI, 13.8 g/L SP, and 14.9 or 5.11 g/L SW, while confirmatory experiments showed a maximum activity of 178 ± 5.2 IU/mL, verifying the validity of the model. The 2nd-order model showed a coefficient of determination (R²) of 0.828. Optimized conditions were used for constant pH fermentations, where a maximum activity of 575 ± 17 IU/mL was achieved at pH 6.5 after 12 h. The adsorption-desorption technique was used to partially purify nisin, followed by drying. The resulting powder showed an activity of 102150 IU/g. Practical Application : Nisin production was optimized using supplemented whey as alternative culture medium, using a native L. lactis UQ2 strain. Soybean peptone, SW, and subinhibitory amounts of nisin were successfully employed to optimize nisin production by L. lactis UQ2. Dried semipurified nisin showed an activity of 102150 IU/g.