We produced nisin from sweet whey, as described above,and labeled it as “nisin produced in-house”. As expected,no cross-contamination was detected. Nisin produced in-house (4982 g/mL total protein; 4 log10AU/mL) was mixedwith ammonium sulphate (1 or 2 M) and tested for antimi-crobial activity and protein content after 24 h. Addition ofammonium sulphate did not change the parameters evalu-ated over time (p < 0.05, T-test).Nisin activity is generally measured by the method usedin this paper, while protein content determination of peptidesvaried greatly. Protein content was first measured using theBradford method, but we did not obtain reproducible resultswhen testing samples with low protein/high nisin content(data not shown). The variability might be due to nisin size(3.4 kDa), which is close to Bradford lower limit (3 kDa), or/andnisin amino acid sequence, which has only five basic groupsto react with the dye. On the contrary, BCA has an expandedlower limit (2 kDa) and reacts with peptide bonds at highertemperatures. Use of BCA in our experiments improved nisindetection and allowed reproducible results.