Evaluation of Growth and Cereulide Production by Bacillus cereus Isolated from Cooked Rice.

Conditions influencing Bacillus cereus growth and cereulide production, such as temperature and
pH, were evaluated at varying incubation periods. The growth and cereulide production at different
temperatures and pH values ranging from 10 to 40 oC and 5.0 to 8.5, respectively showed that the
temperature from 20 to 30 oC and at pH from 6.0 to 7.0 gave the optimum growth and cereulide
production by B. cereus SA105. pH below 6.0 resulted in reduced growth and cereulide production.
Cereulide production increased along with the incubation period, and the maximum cereulide titre
(ng/mL) of 1219.1±8.90 was obtained after 6 days of incubation at 30 oC and pH 6.5 under static
conditions. There was no quantifiable toxin at incubation temperatures of 10 and 40 oC by B. cereus
SA105. This work further reveals that B. cereus growth and cereulide production was significantly
affected by temperature and pH in relation to the incubation period. Furthermore, the findings of
this study will serve as a means for reducing the diversity of the emetic toxin-producing B. cereus
population in food and food products, thus preventing food poisoning.