Optimization of nisin production by Lactococcus lactis

The production of nisin by batch culture of Lactococcus lactis ATCC 11454 in MRS broth (pH 6.5), as treated in 30 assays, that were set up by a fractional factorial design of two levels (2[4–1]), was improved. The minimum and maximum concentrations of sucrose (5.0–12.5 g/L), asparagine (7.5–75 g/L), potassium phosphate (6.0–18.0 g/L), and Tween-80 (1.0–6.6 g/L) were added to MRS broth. The best nisin activities ranged from 1.5×104 to 1.8×104 arbitrary units (AU)/mL for the maximum levels of sucrose, asparagine, and monobasic potassium phosphate, and for the minimum concentration of Tween-80. The best following proportions between nutrients were adopted as optimum for maximum specific nisin productivity of about 6.0 mg/mg of dry cell weight (related to 2.5 mg of pure nisin preparation with a specific activity of 1.0×105 AU/mL): C/N=0.17, C/P=0.69, N/P=4.17 (C=sucrose, N=asparagine, P=phosphate, T=Tween-80).