Sporulation of Bacillus subtilis (natto) KFP 4 isolated from Takahashi natto starter derived from food extracts

We investigated the sporulation of vegetative cells of Bacillus subtilis (natto) KFP 4, isolated from commercial Takahashi natto starter. When the temperature of culture plates was increased from 37 deg C to 40 deg C, the spore number (/ml) after sporulation treatment was observed to increase, and the number of spores was maximized by using cells from the second culture day. In a previous study, the addition of 0.01 mmol/l Mnsup(2+) to the culture medium increased the spore ratio (ratio of spore number to whole cell number) from 72% (data obtained in a previous study) to more than 90%. In the present study, as inorganic Mnsup(2+) was not permitted as a food additive, we prepared extracts from four foods with high Mnsup(2+) content: dry sea lettuce, raw and dry green laver, and poppy seeds. By adding these extracts to the medium we could achieve a spore ratio of more than 90%. There were no large differences in organoleptic test results for natto produced with starters prepared from four kinds of food extracts.