3. FOOD ChEMISTRy & bIOTEChNOLOGy 3.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Food Chemistry & Biotechnology
Fig. 1. Agarose gel electrophoresis of EMA-PCR products
obtained after amplification of purified lactobacillus DNA:
lane 1: EMA treatment, lane 2: no EMA treatment, lane 3: negative
control without DNA, lane 4: positive control with purified
lactobacillus DNA (c DNA = 10 ng μl –1 ), lane 5: DNA standard
(100 bp ladder)
Fig. 2. Agarose gel electrophoresis of EMA-PCR products
obtained after amplification of lactobacillus DNA from yoghurt:
lanes 1, 3, and 5: cells with EMA treatment, lanes 2, 4, and 6:
cells without EMA treatment, lane 9: DNA standard (100 bp
ladder); lanes 1 and 2: 32 days after yoghurt expiration, lanes 3
and 4: not expired, lanes 5 and 6: 12 days after yoghurt expiration,
lane 7: negative control without DNA, lane 8: positive control
with purified lactobacillus DNA (c DNA = 10 ng μl –1 )
not treated cells deffered. On the contrary, in longer expired
yoghurts only dead cells were detected. This is in agreement
with the presumption that non-expired yoghurt samples contain
more viable cells.
s806
Table I
Identification of viable and dead Lactobacillus cells in
yoghurt samples
Yoghurt
expiration
[days]
EMA EMA-PCR Viability
treatment product of cells
non-expired + ++ viable and dead
– +++
12 + + viable and dead
– ++
32 + – dead
– +++
Conclusions
The results presented here show that the method proposed
(ethidium monoazide treated cells in combination with
polymerase chain reaction) is suitable for the distinction of
viable and dead Lactobacillus cells. The method developed
was applied for the analysis of real dairy products (yoghurts).
More viable cells were detected in non-expired yoghurt samples.
The financial support of the National Grant Agency for
Agricultural Research (NAZV) grant No. 1G 57053 and a
long-term research programme of the Ministry of Education,
Youth, and Sports of the Czech Republic (MSM 0021622415)
are gratefully acknowledged. We thank Mr. Ladislav Červený
for his kind language revision.
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