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The combined effect of sub‐optimal temperature and sub‐optimal pH on growth and toxin formation from spores of Clostridium botulinum
Author(s) -
Graham Ann F.,
Lund Barbara M.
Publication year - 1987
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.1365-2672.1987.tb04859.x
Subject(s) - clostridium botulinum , spore , toxin , incubation , growth inhibition , chemistry , divalent , bacterial growth , incubation period , bacteria , food science , microbiology and biotechnology , biochemistry , biology , cell growth , genetics , organic chemistry
Low‐acid foods (pH ≥ 4.5) are not sufficiently acidic to prevent growth of Clostridium botulinum in otherwise optimal conditions. The combination of sub‐optimal pH and sub‐optimal temperature may, however, result in a very significant reduction in the risk of growth of this bacterium compared with the risk in optimal conditions. The combined effect of incubation temperatures of 12° and 16°C and pH values between 5·2 and 5·5 on growth and toxin production from spores of Cl. botulinum during incubation for 28 d has been investigated. Growth and formation of toxin (type B) were detected only in medium at pH 5·5 and incubated at 16°C, corresponding to a probability of growth from a single spore within 14 d of 1·6 × 10 ‐5 . The probability of growth in 28 d in the remaining conditions was <9 × 10 ‐6 . After transfer of inoculated media from 12° to 30°C growth occurred at pH 5·2–5·5 within 19 d. After transfer of inoculated media from 12° to 20°C growth occurred at pH 5·5 and 5·4 but not at pH 5·3 or 5·2 in 40 d. Growth at pH 5·2–5·5 was accompanied by formation of toxin, in most cases of types A or B. In addition to the effect of sub‐optimal temperature and pH, chelation of divalent metal ions by citrate may have contributed to inhibition.