In vitro evaluation of resistance to environmental stress by planktonic and biofilm form of lactic acid bacteria isolated from traditionally made cheese from Serbia

In this study, the effects of different temperature, pH, different concentrations of salt, glucose and lactose, on the planktonic growth, biofilm formation and formed biofilm of Enterococcus hirae KGPMF9, Streptococcus uberis KGPMF2, Lactococcus lactis subsp. lactis KGPMF23 and Lactobacillus fermentum KGPMF29 was investigated. These lactic acid bacteria were previously isolated from traditionally made cheese from Southeastern Serbia. Evaluation of the effect of different environmental conditions on the planktonic growth, biofilm formation and formed biofilm were determined by spectrophotometric method. The limiting factor for the planktonic growth of tested bacteria was the salt concentration above 6.5%, while temperature of 4 degrees C was limiting factor for planktonic growth and biofilm formation. Temperature of 37 degrees C as well as various concentrations of glucose and lactose, stimulated planktonic growth and biofilm formation of all tested bacteria, except E. hirae KGPMF9. S. uberis KGPMF2 showed no ability of biofilm formation. Tested bacteria showed better planktonic growth and ability of biofilm formation in acidic media. Basic media was limiting factor for biofim formation. These results provide a basis for further research of influence of more environmental conditions on the development of lactic acid bacteria and their use like probiotics or starter cultures.