Reuterin production by lactobacilli
isolated from pig faeces
and evaluation of probiotic traits
Rodríguez
et al. (2003) conducted a study to determine the production of reuterin by
lactobacilli isolates from pig faeces and to evaluate their potential as
probiotic bacteria. Thirty-three samples of pig faeces were used to isolate
lactobacilli in this study. Samples were serially dilutions and plated on MRS
agar. All isolates were screened for their reuterin production in the presence
of glycerol by using colorimetric assay at 490 nm. API 50 CHL strips were used for
the biochemical characterization of reuterin-producing isolates. A polymerase
chain reaction (PCR) method based on amplification of 16S RNA coding sequences
of L. reuteri and L. fermentum was used to identify selected
isolates at species level, with primers pairs LOWLAC-REUT1 and LOWLAC-FERM1.
Genomic DNA from L. reuteri CECT 925T and L. fermentum CECT 4007T
were used as control in PCR reactions. Reuterin-producing isolates were exposed
to HCl at pH 3 for 1 h and consecutively to 0.3% oxgall for 1 h to evaluate their
survival under simulate gastric and intestinal conditions. Neutralized
supernatants from cultures grown in MRS broth were used to determine the presence
of bacteriocin-like antimicrobial activity by an agar diffusion assay using Enterococcus
faecalis EF, L. buchneri St2A, Listeria monocytogenes Ohio, L.
plantarum CECT 4645, Clostridium tyrobutyricum NZ8 and E. coli
K12 as indicator strains. Antimicrobial activity was detected by the presence
of inhibition zones. The results showed that 28 of 165 lactobacilli isolates
produced reuterin in the presence of glycerol. Six isolates yielding high
levels of reuterin (> 15 mg/mL) with respect to type strain Lactobacillus
reuteri CECT 925T were identified as L. reuteri. They were able to
survive at pH 3 and subsequent exposure to 0.3% oxgall and presented bacteriocin-like
activities. The researchers suggested that high yields of reuterin may be
obtained from selected isolates of L. reuteri. Probiotic characteristics
of isolates studied could be applied in food and feed. However there are some
limitations.
1)
Resistance to low pH and bile salts in this study under simulate gastric and
intestinal conditions in this study were not correlated with presented conditions
in stomach and small intestine. According to Argyri et al.
(2013), resistance
to bile salts was assessed in terms of viable colony counts and enumerated
after incubation culture in medium with 0.5% bile salts at 37 °C
for 0, 1, 2, and 4 h, reflecting the time spent by food in the small intestine.
For evaluation of resistance to low pH, the experiment was performed by incubation
culture in medium with pH 2.5 at 37 °C for 0, 0.5, 1,
2, and 3 h, reflecting the time spent by food in the stomach.
2)
Neutralized supernatant used for determination of bacteriocin-like
antimicrobial activity could not exclude the inhibitory effect of other
antimicrobial substances such as hydrogen peroxide and diacetyl which produced
by lactobacilli. Therefore, inhibitory effect might not be from
bacteriocin.
The
strength of this study is that biochemical characterization and PCR
amplification of 16S RNA coding sequences used are widely accepted in many
laboratories for bacterial identification in genus and species levels,
respectively. Especially, 16S RNA coding sequences could differentiate
bacterial species up to 99%. Another advantage of this study is that the
results were clearly described with text, table, figures and
conclusion which were made relation to results in this study.
References
Rodríguez, E., Arqués, J.L.,
Rodríguez, R., Nuñez, M. and Medina, M. (2003). Reuterin production by
lactobacilli isolated from pig faeces and evaluation of probiotic traits. Letters
in Applied Microbiology, 37: 259-263
Argyri, A. A., Zoumpopoulou, G., Karatzas,
K. -A. G., Tsakalidou, E., Nychas, G. –J. E., Panagou, E. Z., and Tassou, C. C.
(2013). Selection of potential probiotic lactic acid bacteria from fermented
olives by in vitro tests. Food Microbiology, 33: 282-291.
Hi
ReplyDeleteline 29 "salts was assessed in terms of viable colony counts and enumerated..."
I think that after and. you should be used "verb"
I not sure :)
Hi Sujitra Jaa
ReplyDeleteFollowing the web (https://www.library.cornell.edu/research/citation/apa), they tell that " Write out the last name and initials for all authors of a particular work. Use an ampersand (&) instead of the word "and". "
So in APA style reference "and" should be changed to "&" . ^ ^
Hi Sijitra
ReplyDeleteI think you should be full term of each abbreviated word; for example, MSR agar and API 50 CHL strips.
Thank you for all comments ka.
ReplyDelete