The Preliminary Research Of Biological Properties Of Bacillus Natto Spores

Fifty strains were screened from fermentation bed material according to the biological qualification of hydrolyzing starch of Bacillus natto. Three Bacillus strains were re-screening by fiber protease activity. At last, we confirmed that J22 strain was Bacillus natto by physiological and biochemical characters test.Bacillus natto spores prepared at higher temperatures were more resistant to wet heat than were spores prepared at lower temperatures. Spores prepared at higher temperatures were also more resistant to hydrogen peroxide, formaldehyde. However, spores prepared at higher temperatures were less osmoresistant and spores prepared at high and low temperatures exhibited nearly identical resistance to u.v. radiation and dry heat. The temperature of sporulation affects a number of spore properties, including resistance to many different stress factors. The precise conditions for the formation of B. natto spores have a large effect on many spore properties.Superdormant spores of Bacillus natto were isolated in 4 to 12% yields following germination with high nutrient levels that activated one or two germinant receptors. These superdormant spores did not germinate with the initial nutrients or those that stimulated other germinant receptors, and the superdormant spores’ defect was not genetic. The superdormant spores did, however, germinate with Ca2+-dipicolinic acid. Although these superdormant spores did not germinate with high levels of nutrients that activated one or two nutrient germinant receptors, they germinated with nutrient mixtures that activated more receptors, and using high levels of nutrient mixtures activating more germinant receptors decreased superdormant spore yields.The use of moderate nutrient levels to isolate superdormant spores increased their yields; the resultant spores germinated poorly with the initial moderate nutrient concentrations, but they germinated well with high nutrient concentrations. These findings suggest that the levels of superdormant spores in populations depend on the germination conditions used, with fewer superdormant spores isolated when better germination conditions are used. These findings further suggest that superdormant spores require an increased signal for triggering spore germination compared to most spores in populations. An important factor may be heat activation of spore populations, since yields of superdormant spores from non-heat-activated spore populations were higher than those from optimally activated spores.Purified superdormant spores of Bacillus natto isolated after optimal heat activation of dormant spores and subsequent germination with L-valine, germinate very poorly with the original germinants used to remove dormant spores from spore populations, thus allowing isolation of the superdormant spores, and even with alternate germinants. However, these superdormant spores exhibited significant germination with the original or alternate germinants if the spores were heat activated at temperatures 5 to 10℃ higher than the optimal temperatures for the original dormant spores, although the levels of superdormant spore germination were not as great as those of dormant spores. Use of mixtures of original and alternate germinants lowered the heat activation temperature optima for both dormant and superdormant spores. The superdormant spores had higher wet-heat resistance than the original dormant spore populations. These results provide new information about the germination, heat activation optima, and wet-heat resistance of superdormant spores and the heterogeneity in these properties between individual members of dormant spore populations.