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

Abstract

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 ºC. 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 α-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.

Intestinalni izolati Lactobacillus sp. V3 i Bifidobacterium sp. A71 su izabrani za fermentaciju sojinog mleka prema pokazanoj acidifikacionoj aktivnosti u sojinom mleku. Sok cvekle i mrkve su izabrani za obogaćivanje sojinog mleka kao dodatni izvor ugljenih hidrata a autolizat pivskog kvasca kao dodatni izvor azota. Fermentacija je vršena u toku osam sati na 42 ºC i praćena je standardnim analitičkim i mikrobiološkim testovima koji su obuhvatali promenu aciditeta (pad pH i povećanje sadržaja kiselina), promenu sadržaja rastvorne suve supstance, promenu sadržaja šećera (izraženih preko glukoze) i α-amino azota, kao i promenu broja živih ćelija. Uzorkovanje je vršeno pre početka fermentacije i na svaka dva sata do kraja praćenog perioda fermentacije. Rezultati su pokazali da postoje razlike između testiranih izolata u pogledu sposobnosti fermentacije sojinog mleka. Smeša pojedinačnih sokova sa autolizatom pivskog kvasca je pokazala bolji stimulativni efekat na rast i biohemijsku aktivnost oba soja, u poređenju sa samim sokovima. Dodatno, sok mrkve je bolji stimulant za rast soja Bifidobacterium sp. A71 u poređenju sa sokom cvekle, dok je obrnuti efekat utvrđen za rast Lactobacillus sp. V3.