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Influence of pH and lactic acid concentration on Clostridium tyrobutyricum during continuous growth in a pH‐auxostat
Author(s) -
Thylin I.,
Schuisky P,
Lindgren S.,
Gottschal J. C.
Publication year - 1995
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.1365-2672.1995.tb00952.x
Subject(s) - lactic acid , chemistry , fermentation , food science , chromatography , bacteria , biology , genetics
The aim of this project was to establish the minimal inhibitory concentration (MIC) of lactic acid for growth of Clostridium tyrobutyricum. A pH‐auxostat was used to maintain a constant pH and to allow continuous growth at the highest possible rates at fixed, but adjustable concentrations of lactate. By raising the concentration of lactic acid and keeping the pH constant, the growth rate was shown to decrease linearly with increasing lactic acid concentration. The p K a of lactic acid, measured in the actual growth medium at 37°C, was 3.40 (±0.03). Based on this value, the MIC undiss values for each pH were estimated. The MIC of total lactic acid (MIC tot ) ranged from 150 mmol l −1 to 1510 mmol l −1 at pH 4.6–6.25, respectively. The corresponding MIC values of undissociated lactic acid (MIC undiss ) ranged from 8.9 to 2.1 mmol l −1 at the same pH values. These results emphasize the importance of a rapid pH decrease and an equally rapid initial lactic acid fermentation of the ensilage, in order to sufficiently suppress clostridial growth.