A culture medium for L. sakei (SAK-medium) was initially used, having the following composition: meat extract, ME (VWR) 8 g/L; yeast extract, YE (Costantino srl, Turin, Italy) 8 g/L; arginine, ARG (Merck K GaA) 0.5 g/L; Tween-80 (Merck K GaA) 0.5 mL/L, minerals and vitamins mix 1 mL/L as reported by Mapelli et al. [27 (link)]. Ingredients were dissolved in liquid CWP, kindly supplied by Latteria Soresina (Soresina, Italy).
Freshly produced CWP was collected at the cheese factory from the UF plant that processes whey from hard cheese manufacture, immediately frozen and kept at −20 °C until use. The CWP batch had a lactose content of 42 g/L and pH 6.2 and was filter sterilized just before use.
Both L. sakei growth and sakacin A production were determined in the SAK-medium and in MRS, being the latter taken as benchmark. L. sakei growth was studied at 26°C with different percentage of inoculum, i.e., 0.1, 0.5, 1 and 5% (v/v). Culture turbidity (OD) was measured spectrophotometrically at 600 nm every 15 min in a PowerWave™ XS2 Microplate Spectrophotometer (BioTek, Winooski, VT, USA); lag phase (min) and maximum growth rate (OD/h) were determined fitting data through the Baranyi and Roberts model [31 (link)] on DMFit 3.5 Excel add-in.
Freshly produced CWP was collected at the cheese factory from the UF plant that processes whey from hard cheese manufacture, immediately frozen and kept at −20 °C until use. The CWP batch had a lactose content of 42 g/L and pH 6.2 and was filter sterilized just before use.
Both L. sakei growth and sakacin A production were determined in the SAK-medium and in MRS, being the latter taken as benchmark. L. sakei growth was studied at 26°C with different percentage of inoculum, i.e., 0.1, 0.5, 1 and 5% (v/v). Culture turbidity (OD) was measured spectrophotometrically at 600 nm every 15 min in a PowerWave™ XS2 Microplate Spectrophotometer (BioTek, Winooski, VT, USA); lag phase (min) and maximum growth rate (OD/h) were determined fitting data through the Baranyi and Roberts model [31 (link)] on DMFit 3.5 Excel add-in.
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