The oxalate-degrading activity of Lactobacillus spp. isolated from different sources as the potential probiotic modulators for oxalate homeostasis

Abstract

Background: Currently, diseases of the urinary system are observed in 3.5–4% of the world's population. According to WHO, the number of people suffering from this pathology doubles every 7–10 years. To date, hyperoxaluria is considered as the main risk factor for the formation of oxalate-calcium stones, which account for 75% of all kidney stones. One of the main causes of hyperoxaluria is a decrease in the number of microorganisms capable of degrading oxalates, which occurs due to the disruption of the intestinal microbiota. Oxalate-degrading bacteria include the genera Lactobacillus, Bifidobacterium, Oxalobacter formigenes etc. Searching of probiotic strains with high oxalate-degrading activity have become one of the priorities from the context of research. The aim of the present study was to isolate Lactobacillus spp from different sources and to determine their ability to degrade oxalate. Methods: A total of 23 Lactobacillus spp. from food of animal and vegetable origin were isolated with selective MRS Broth medium and further cultured on MRS Agar or Oxalate Medium with 5 g/l sodium oxalate. ANAERO test23 was used to assess the species affiliation. Oxalate-degrading activity (ODA) was measured by redox titration with KMnO4. Results: Only 7 species of isolated bacteria out of 23 showed the ability to grow on the oxalate-containing culture medium. According to the morphological and physiological-biochemical characteristics, these bacteria belonged to the genus Lactobacillus: L. nagelii – 2 spp, L. rhamnosus – 2 spp., L. frumenti - 1 spp, L. plantarum – 1 spp, L. acidophilu – 1 spp. The most active metabolizers of oxalate on Oxalate Medium were L. plantarum S3 – 42%; L. acidophilus S5 – 38%, and L. nagelii Z2 – 35%; the worst results were shown by L. rhamnosus K7 and L. nagelii S12 – both metabolized only 7% of sodium oxalate. Conclusions: The redoximetric titration with KMnO4 was adopted to evaluate the ODA of bacteria in culture media. Lactobacillus spp. isolated from different sources differs according to the level of ODA. Three promising Lactobacillus species were selected for further estimation of probiotic profile.