Thesis (MSc (Microbiology))--Stellenbosch University, 2008. / Lactobacillus plantarum JW3BZ and Lactobacillus fermentum JW15BZ isolated from boza, a
Bulgarian cereal based fermented beverage, produce bacteriocins JW3BZ and JW15BZ active
against a wide range of food spoilage and pathogenic bacteria. Strains JW3BZ and JW15BZ
are resistant to low pH (pH 2.0–4.0). Both strains grow well in MRS broth with an initial pH
ranging from 5.0 to 10.0. Strain JW3BZ displayed intrinsic resistance to bile salts. Strain
JW15BZ, on the other hand, is sensitive to bile salts exceeding concentrations of 0.3% (w/v).
Both strains are weakly hydrophobic and are resistant to a wide range of antibiotics, antiinflammatory
drugs and painkillers. Strains JW3BZ and JW15BZ adhered at 4% to Caco-2
cells and they did not compete with Listeria monocytogenes Scott A for adhesion. A
homologue of MapA, a gene known to play a role in adhesion, was detected in L. plantarum
JW3BZ. Both strains have high auto- and co-aggregation properties.
Bacteriocin JW15BZ was partially purified with ammonium sulfate, followed by separation
on Sep-Pak C18 and reverse phase High Pressure Liquid Chromatography (HPLC). Two
separate peaks with antimicrobial activity were recorded for bacteriocin JW15BZ, suggesting
that it consists of at least two antimicrobial peptides. Lactobacillus plantarum JW3BZ
contains genes homologous to plnE, plnF and plnI of the plnEFI operon that encode for two
small cationic bacteriocin-like peptides with double-glycine-type leader peptides and its
respective immunity proteins. The antimicrobial activity displayed by strain JW3BZ may thus
be ascribed to the production of plantaricins E and F. Bacteriocin JW3BZ and JW15BZ
displayed activity against herpes simplex virus (HSV-1) (EC50=200 μg/ml).
Both strains were identified in boza after 7 days at storage at 4 oC and repressed the growth of
Lactobacillus sakei DSM 20017, indicating that the bacteriocins are produced in situ. The
sensory attributes of boza prepared with different starter cultures did not vary considerably,
although statistical differences were observed for acidity and yeasty aroma.
Encapsulation of strain JW3BZ and JW15BZ in 2% sodium alginate protected the cells from
low pH (1.6) and 2.0% (w/v) bile. The rate at which cells were released from the matrix
varied, depending on the conditions. Better survival of strains JW3BZ and JW15BZ
encapsulated in 2% (w/v) alginate was observed during 9 h in a gastro-intestinal model.
Highest release of cells was observed at conditions simulating colonic pH (pH 7.4), starting from 56-65% during the first 30 min, followed by 87%. Complete (100%) release was
recorded after 2.5 h at these conditions.
Strains JW3BZ and JW15BZ could be used as starter cultures in boza. The broad spectrum of
antimicrobial activity of bacteriocins JW3BZ and JW15BZ is an added advantage, rendering
the cells additional probiotic properties. Encapsulation of the cells in alginate gel increased
their resistance to harsh environmental conditions and may be the ideal method to deliver
viable cells in vivo.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/2174 |
| Date | 03 1900 |
| Creators | Von Mollendorff, Johan Wilhelm |
| Contributors | Dick, L. M. T., Stellenbosch University. Faculty of Science. Dept. of Microbiology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | Stellenbosch University |
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