Comparative study on biochemical activity of the intestinal isolates Lactobacillus sp. V3 and Bifidobacterium sp. A71 in different substrates

The two intestinal isolates Lactobacillus sp. V3 and Bifidobacterium sp. A71 were selected for soymilk fermentation according to their acidification activity in soymilk. Beetroot juice and carrot juice were chosen for soymilk supplementation as additional sources of carbohydrates and brewer's yeast as an extra source of nitrogen. The fermentation was carried out for eight hours at 42°C. The fermentation was monitored by standard analytical and microbiological tests for changes of acidity (decreasing pH and increasing acid content), the contents of soluble dry substances, sugars and a-amino acids as well as changes in the number of viable cells. The samples were collected at the beginning and subsequently every two hours until the end of the fermentation. The results showed that there were differences between the tested isolates in terms of their ability to ferment soymilk. The mix with brewer's yeast had a better stimulating effect on the growth of both strains compared to those with juices alone. In addition, the carrot juice stimulated the growth of Bifidobacterium sp. A71 better than beetroot juice, while the opposite effect was found for the growth of Lactobacillus sp. V3.