Fig. 2

Comparison of automated (upper panel) and manual (lower panel) pHluorin2 assay results of nine random samples of supernatants of L. sakei A1608 (S1-S5) or L. lactis B1629 using sensor strain L. innocua LMG2785/pNZ-pHin2^Lm for determination of antimicrobial activity in bacteriocin units. NC/PC: Green—negative control (LMBO buffer); red—positive controls (left: LMBO containing 0.01% CTAB, right: M17 complex medium diluted fourfold in LMBO containing 0.01% CTAB). Nis: LMBO containing nisin in concentrations 0.128, 0.5, 1.25, 2.5 and 5 µg mL⁻¹. Controls and standards were measured in technical triplicates. Sample dilutions were measured in unicates. 50% threshold is calculated from mean ratios of negative control and 5 µg mL⁻¹ nisin. Measurements from undiluted cultivation supernatant were not analyzed due to interference of complex media with fluorescence measurement