Abstract:
This research aims to determine the fermentation conditions and
viability in a medium simulating the gastrointestinal tract and to examine the
antagonistic potential of Lactobacillus acidophilus (Lb. acidophilus) and
Lactobacillus rhamnosus (Lb. rhamnosus) in producing a lactose-free
starter. Our study examined Lactic Acid Bacteria (LAB). The sources of
Lb. acidophilus strains are camel milk (shubat), Lb. rhamnosus mare milk
(koumiss), traditional homemade dairy foods in Kazakhstan. Lb. acidophilus
and Lb. rhamnosus are resistant to gastric juice acidity at a pH above 3,
therefore they will be able to pass through the stomach intact. The cell
populations remained ≥106 CFU mL. When Lb. acidophilus was treated at
pH 3.0-5.0, the cell population was significantly higher (p≤0.05). Simulated
gastrointestinal transit was studied by assessing NaCl resistance. The cell
counts in the medium with 5% NaCl were significantly higher (p≤0.05) than
those in the medium with 2% NaCL. Lb. acidophilus and Lb. rhamnosus
showed growth corresponding to ~7 log CFU at 5-7% NaCl. Lb. acidophilus
and Lb. rhamnosus were tested for their antibacterial activity by agarwell diffusion test. Three common pathogens, E. coli, S. marcescens, and
S. Typhimurium were used for the investigation of antagonistic activity.
Lb. acidophilus and Lb. rhamnosus showed significantly high inhibition
zone ranges (p≤0.05) from 10-12 mm against E. coli and S. marcescens. A
medium zone of inhibition 5.0-6.0 mm against S. typhimurium. For cofermentation, pasteurized milk inoculated with Lb. acidophilus and Lb.
rhamnosus cells were fractionated into 25 mL portions and placed in 50 mL
conical tubes. It was spread on a nutrient medium of Petri dishes and
incubated for 24 h at 37°С. Lb. acidophilus and Lb. rhamnosus starter
culture reached a significant cell population of about ~8 logs Colony
Forming Unit (CFU/mL) during co-culture fermentation, pH in
Pasteurized Milk (PM) rapidly decreased to 3.0.
