Survival of Lactic Acid Bacteria and Their Lactases under Acidic Conditions

Abstract

Effects of sonication, survival, and p-galactosidase activity of four lactic cultures were investigated in pH 1.5-3.5 range. Lactobacillur delbruekii subsp. bulgaricus and Streptococcus thermophilus exhibited the highest P-galactosidase activity in skim milk and broth systems, respectively. The P-galactosidases from L. delbruekii subsp. bulgaricus, S. thennophilus, and L. acidophilus showed optimum activity in the neutral pH range and 55°C. Viable count of all four cultures decreased most rapidly at pH 1.5, but L. acidophilus and L. detbruekii subsp. bzd~uricus survived better than the other organisms. The decrease of enz$ne activity of unsonicated cultures withpH was slight. esneciallv at DH 3.5. However. acidification of sonicated cultures to PH 3.5 or'lower resulted in rapid and permanent loss of enzyme activity.

Producing Probiotic Peach Juice

“…The viability of probiotic organisms is also influenced by inhibitory components such as lactic acid during fermentation and cold storage. Some other Conditions such as increased acidity resulting from the fermentation process can reduce the survival and viability of probiotic bacteria (16,(20)(21)(22). As mentioned above, we found that L. delbrueckii and L. plantarum could survive the high acidity and low pH in fermented peach juice.…”

Viability of Probiotic Bacteria during Refrigerated Storage of Commercial Probiotic Fermented Dairy Products Marketed In Jordan

“…Although L. acidophilus and bifidobacteria tolerate acid, a rapid decline in their numbers in yogurt has been observed (Shah and Jelen, 1990). …”

Influence of “Mild” Sonication Conditions on the Characteristics of <i>Streptococcus thermophilus</i> ST-M5

“…Shah and Jelen [28] reported that Lactobacillus bulgaricus exhibited higher β-galactosidase activity than Streptococcus thermophilus and Lactobacillus acidophillus. Additionally, Wang et al [31] sonicated samples of Lactobacillus delbrueckii ssp.…”

“…Clark and Martin [27] reported that in the presence or absence of bile acid (Oxgall), B. longumand Lactobacillus bulgaricustolerated bile concentrations as high as 4.0%. Furthermore, Shah and Jelen [28] have attributed increased bile tolerance of Lactobacilli strains to their rigid cell wall. There could be other factors responsible for increased bile tolerance of Lactobacillus bulgaricus and Streptococcus thermophilus when subjected to mild sonication conditions.…”