Scientific journal

49 2010

Journal of Food and Nutrition Research
Summary No. 1 / 2010

Effect of some environmental factors on autolysis of lactococci used for cheese production
Journal of Food and Nutrition Research, 49, 2010, No. 1, s. 1-9

Milada Plocková, Department of Dairy and Fat Technology, Institute of Chemical Technology, Prague, Technická 5, CZ – 166 28 Prague 6, Czech Republic. E-mail:, tel.: +420 220 443 275

Summary: About 300 strains were isolated from different sources and phenotypically identified. Twenty-three of them, identified as Lactococcus lactis, were subjected to genotypic characterization and tested for autolytic activity. These strains were subdivided by the plasmide profile technique into 4 clusters, each containing the isolates that shared the same plasmid pattern. Three strains showed completely different plasmid profiles. Three highly autolytic strains were found among 23 isolates. One of them, Lactococcus lactis HMM81, which exhibited the highest autolytic activity in citrate buffer (approximately 48%), was chosen for further investigation of factors influencing the autolysis. These comprised extrinsic factors (incubation temperature) and intrinsic factors (NaCl concentration, pH of the medium, citrate buffer concentration, growth phase). As a reference strain, a non–autolytic strain Lactococcus lactis subsp. lactis NIZO B643 was used. Based on the investigation of the extrisic and intrinsic factors, the most suitable conditions for fast prediction of autolytic activity of a strain were suggested: pre-incubation for 6 h at 30 °C, re-suspendation of cells in 50 mmol•l-1 sodium citrate buffer (pH 5.0, containing 15 g•l-1 NaCl) and cultivation at 30 °C for 6 days.

Keywords: Lactococcus, autolysis, prediction, citrate buffer

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