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Applied and Environmental Microbiology, June 2001, p. 2699-2704, Vol. 67, No. 6
Dairy Products Research Centre, Fermoy,
County Cork,1 and Department of
Microbiology2 and National Food
Biotechnology Centre,3 University College, Cork,
Ireland
Received 3 September 1999/Accepted 21 March 2001
The aim of the present study was to develop adjunct strains which
can grow in the presence of bacteriocin produced by lacticin 3147-producing starters in fermented products such as cheese. A
Lactobacillus paracasei subsp. paracasei
strain (DPC5336) was isolated from a well-flavored, commercial cheddar
cheese and exposed to increasing concentrations (up to 4,100 arbitrary
units [AU]/ml) of lantibiotic lacticin 3147. This approach
generated a stable, more-resistant variant of the isolate (DPC5337),
which was 32 times less sensitive to lacticin 3147 than DPC5336. The
performance of DPC5336 was compared to that of DPC5337 as adjunct
cultures in two separate trials using either Lactococcus
lactis DPC3147 (a natural producer) or L. lactis
DPC4275 (a lacticin 3147-producing transconjugant) as the starter.
These lacticin 3147-producing starters were previously shown to control
adventitious nonstarter lactic acid bacteria in cheddar cheese.
Lacticin 3147 was produced and remained stable during ripening, with
levels of either 1,280 or 640 AU/g detected after 6 months of ripening.
The more-resistant adjunct culture survived and grew in the presence of
the bacteriocin in each trial, reaching levels of 107 CFU/g
during ripening, in contrast to the sensitive strain, which was present
at levels 100- to 1,000-fold lower. Furthermore, randomly amplified
polymorphic DNA-PCR was employed to demonstrate that the resistant
adjunct strain comprised the dominant microflora in the test cheeses
during ripening.
0099-2240/01/$04.00+0 DOI: 10.1128/AEM.67.6.2699-2704.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Strategy for Manipulation of Cheese Flora Using
Combinations of Lacticin 3147-Producing and -Resistant
Cultures
*
Corresponding author. Mailing address: Dairy Products
Research Centre, Moorepark, Teagasc, Fermoy, Co. Cork, Ireland. Phone: 353-25-42229. Fax: 353-25-42340. E-mail:
pross{at}moorepark.teagasc.ie.
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