African Journal of
Microbiology Research

  • Abbreviation: Afr. J. Microbiol. Res.
  • Language: English
  • ISSN: 1996-0808
  • DOI: 10.5897/AJMR
  • Start Year: 2007
  • Published Articles: 5233

Full Length Research Paper

The physiological state of Lactoccocus lactis and Propionibacterium freudenreichii strains in co-cultures induced by low temperature and osmotic stress

  Justyna Borawska1, Marta Mikš-Krajnik2* and MaÅ‚gorzata Darewicz1
  1Department of Food Biochemistry, Faculty of Food Science, University of Warmia and Mazury in Olsztyn, Poland. 2Department of Industrial and Food Microbiology, Faculty of Food Science, University of Warmia and Mazury in Olsztyn, Poland
Email: [email protected]

  •  Accepted: 25 March 2013
  •  Published: 19 July 2013



The bacterial physiological state, type of interactions and changes in metabolism ofLactococcus lactis and Propionibacterium freudenreichii strains in co-culture were studied in skimmed milk in response to osmotic [3% (w/v) NaCl] and low temperature (10°C) stress during long-term incubation. Changes in the integrity of cell membrane were examined by LIVE/DEAD® BacLight™ staining, and culture viability and bacterial interactions studies were performed with the use of the plate count technique. The profiles of volatile organic compounds were assessed by static headspace-gas chromatography. During the stationary growth phase, the number of LIVE cells with intact membranes was reduced in the presence of NaCl in comparison with control conditions, and a longer adaptation phase was observed at 10°C. The viability of starter cultures was high at ~108to 109 CFU/ml at the end of the experiment in all tested conditions. Our results point to the possibility of commensalisms interactions between lactic acid and propionic acid bacteria. Prolonged culture incubation contributed to the accumulation of acetoin, and it enhanced acetic acid and propionic acid synthesis during the stationary growth phase of propionic acid bacteria.


Key words: Lactococcus lactisPropionibacterium freudenreichii, viability, volatiles compounds, osmotic stress, low temperature stress.


 LAB, Lactic acid bacteria; PAB, propionic acid bacteria; VBNC, viable but not culturable; PI, propidium iodide; UHT, ultra high temperature; DEFT, direct epifluorescent filter technique; HS, headspace; GC, gas chromatography; FID, flame ionization detector; FISH, fluorescent in situ hybridization.