solvents. The use of lactic-acid bacteria for the manufacture of products (beverages)
with curative and prophylactic effect is substantiated not only by the accumulation of
lactic acid, which suppresses putrid and pathogenic microbiota. The therapeutic
function of lactic-acid bacteria is also characterized by the synthesis of antibiotics with
a relatively high activity.
It is believed [9] that specific antagonism phenomenon arises from a complex
effect of these factors, since it has not been established yet the clear difference between
antibiotic effect and lactic-acid inhibitive effect [9]. Despite the fact that lactobacilli
antibiotics, for example lactams in L. plantarum or lactocidine in L. acidophilus, have
been known for a long time, their pharmaceutical forms are still absent in pharmacies.
This increases the reasonability of lacto-fermented food and beverages application for
therapeutic use.
Within this context, we evaluated the antagonistic activity of metabolites,
produced by L. casei ssp. аlactosus strains' regarding Enterobacteriaceae: sanitary
indicator strain of Escherichia coli 055 and pathogenic strain of Salmonella
typhimurium DISK 144. Cells' suspension of one of the test cultures, containing
approximately 105 CFU/1 cm
3
, was applied in a volume of 1 cm
3
into test tubes
containing 10 cm
3
of birch sap, fermented with strain No. 6 or No.12. The control was
the same suspension applied into the saline solution. The obtained mixtures were stored
at room temperature with no exposure to light. Inoculations on Endo medium (E. coli)
and bismuth sulfite agar (S. typhimurium) were made immediately after test cultures'
application, and then in 30 and in 60 minutes.
Calculation of colonies (test-cultures that grew in three parallel experiments after
inoculation into the tubes with fermented juice and control tubes with saline solution)
showed that their number decreased by about two times as compared to initial strains
No. 6 and No.12 after 30 minutes exposure in the fermented juice. After 1 hour
exposure the sanitary indicative and pathogenic Enterobacteriaceae were not detected.
These results are given in Table 4.
Table 4 Antimicrobial activity of birch sap fermented by
L. casеi ssp. аlactosus strains regarding some Enterobacteriaceae (n=3, р≥0,95)
Test-culture
Variant
Strain
number
Test-cultures number (CFU/ 1см
3
х 10
3
) after contact
with fermented juice (hours)
0
30
60
E. сoli 055
Control
-
6.4…7.1
6.0…6.7
5.8…6.0
Experiment
6
5.3…6.9
2.0…3.0
Not detected
12
6.5…7.0
3.1…3.7
Not detected
S. typhimurium
Control
-
8.1…8.8
7.9…8.3
7.7…7.9
Experiment
6
5.8…7.2
3.0…4.0
Not detected
12
8.3…8.6
3.7...4.9
Not detected
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