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Pediocin 5 production and plasmid stability during continuous free and immobilized cell cultures of Pediococcus acidilactici UL5
Author(s) -
Huang J.,
Lacroix C.,
Daba H.,
Simard R.E.
Publication year - 1996
Publication title -
journal of applied bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 0021-8847
DOI - 10.1111/j.1365-2672.1996.tb03268.x
Subject(s) - pediococcus acidilactici , plasmid , biology , chemistry , microbiology and biotechnology , dna , bacteria , biochemistry , genetics , lactic acid , lactobacillus plantarum
Continuous production of pediocin 5 from Pediococcus acidilactici UL5 was investigated in MRS medium at different pH and dilution rates during continuous free cell (FC) and immobilized cell (IC) fermentations. Pediocin 5 activity from FC operated at a dilution rate of 0·31 h −1 largely increased from 128 to 2048 AU ml −1 as pH decreased from 7·0 to 5·0. Pediocin 5 activity in IC at a dilution rate of 0·93 h −1 was much less affected by pH, varying from 256 AU ml −1 at pH 7·0 to 512 AU ml −1 at pH 5·0. At the optimum pH 5·0, the dilution rate greatly influenced pediocin 5 activity both in FC and IC. Pediocin 5 production during continuous FC culture decreased with time for all dilution rates tested except 0·31 h −1 and average activity over 144 h cultures reached a maximal value of 4915 AU ml −1 at a dilution rate of 0·26 h −1 . For IC, pediocin 5 production was stable with time and increased with the dilution rate from 256 to 1024 AU ml −1 in the range of 0·47‐2·28 h −1 . Three Listeria strains were tested for their ability to screen low bacteriocin‐producing variants (Bac v + ) of Bac + cells in FC and IC cultures by using a modified deferred antagonism method. Ten to 28% of Bac v + cells appeared after 144 h of FC cultures at dilution rates in the range 0·09‐0·42 h −1 and pH control set points of 5·0‐7·0 while almost no Bac v + cell was detected during 192 h IC culture in the same pH range and for dilution rates varying from 0·47 to 2·28 h −1 . The Bac v + cells isolated produced eight‐ to 64‐fold less pediocin 5 than the Bac + cells. Although electrophoresis analysis showed no apparent difference in the plasmid profiles of Bac v + and Bac + cells, the Bac − mutant obtained by acriflavine treatment had lost the pMJ5 plasmid encoding for bacteriocin production. The decreased quantity of plasmid DNA in Bac v + cells suggests that the decreased pediocin 5 activity of Bac v + cells resulted from a decrease in plasmid copy number.