Abstract:
Pediococcus acidilactici CP7-3 and Weissella confusa CP3-1 were lactic acid
bacteria (LAB) isolated from Thai traditional fermented sausage and previously reported
to have bacteriocin-like activity. This research aimed to study the growth phase of those
two LAB in batch culture and determined their bacteriocin activity in each phase of
growth. Four culture media were compared i.e. Trypic soy broth plus 3% yeast extract
(TSBYE), MRS broth normal formula, MRS broth without glucose (MRSNG) and
coconut water broth (CWM). The results showed that the strain CP7-3 had higher
growth than the strain CP3-1 in all media. Furthermore the bacteriocin activity against
indicator microorganism (Bacillus cereus and Staphylococcus aureus) seemed to relate
with the growth phase. and a further decreased at the end of growth in the media
without glucose (TSBYE and MRS-NG) where the pH remained at 6.0. the inhibitory
activity also decreased at the end of the growth . Both Bacteriocin CP3-1 and CP7-3
produced by LAB in MRS broth and CWM. Although the BUmax of the two LAB strains
in the media with glucose (MRS and CWM) were high at 3.6-4.6 B.U./ml , this due to
the synergistic role of lactic acid produced and the drop of pH, the high number of cells
and bacteriocin production all together. The filtrate from CP7-3 showed inhibitory activity
against both of B. cereus and S. aureus but the filtrate from CP3-1 showed low
inhibition to B. cereus. Thereafter, filtrate from CP3-1 and CP7-3 were partially into 3
different range Pellicorn membrane and were partialy purified by choloform extraction
and ammonium sulphate precipitation. The results showed that inhibitory activity of
CP7-3 appeared at the range of ≤ 5 kDa. In contrast the activity of CP3-1
insuppressing B. cereus revealed at ≥ 10kDa, though the inhibition of S. aureus showed
at < 5 kDa. The amino acid components of peptides from CP3-1 were analyzed. There
were aspartic acid, glutamic acid, lysine, threonine and valine, however aspartic acid
and glutamic acid seem to involve in the bacteriocin. The smaller size of peptide from
CP3-1 (smaller than 5 kDa) composed of aspartic acid, glutamic acid, lysine, valine,
leucine and isolecine. This research had suggested the potential of novel bacteriocin
produced by W. confusa CP3-1 and its possible amino acid components which may be
useful for being bio-preservative in the future.