Abstract
It has been shown in the preceding paper that interior portion of fish jelly products (Kamaboko) or fish sausage is being kept in a condition of rather low oxidation-reduction potential, Eh value likes range between -0.100 and -0.250 volts.
Taking into consideration of this factor, the present report dealt with observation of the growth under different level of oxidation-reduction potential for some varieties of Bacillus group including both type strains and the organisms isolated from commercial fish sausage.
In a test with glucose-agar medium, 11 strains from 21 strains of Bacillus species failed to grow where the initial Eh value was adjusted to -0.2 volt with thioglycolic acid, however, none of the strain of Bacillus megaterium tested could indicate growth. These findings were never shifted to any other pattern, even when yeast extract was added to the medium, but most strains lost ability to grow on the medium lacking glucose, while in the medium containing starch in stead of glucose, the majority of strains showed fairly good growth as in glucose-agar medium. These results suggest that Bacillus species normally need certain fermentative sugarfor their growth in low potential condition.
The lowest Eh value of the glucose-agar medium which enables growth of these strictly aerobic Bacilli was found to be near +0.20 volt for both spores and vegetative forms. On the other hand, in a medium without glucose, these microorganisms required a condition in which the minimum Eh value should be kept above +0.24 volt.
The growth of facultative aerobic strains, capable to grow even at low potential, was also affected by the change in oxidation-reduction potential of media. Under circumstance of high potential such as the Eh above +0.23 volt, facultative aerobes showed much vigorous development, but if the potential of medium would turn to negative region, these strains could grow only in less extent. And also, some strains of this group were no more able to grow at the Eh below -0.25 volt and in addition, the colonies formed in agar medium became to decrease in their number in accordance with reduction of the potential.
