Development of low-flavor natto manufactured with leucine-requiring mutants of elastase-producing natto Bacillus [Japanese]

摘要

Since one of the natto flavor components, 3-methyl butanoate is a metabolite of leucine, two leucine-requiring mutants of elastase-producing Bacillus subtilis (natto) KFP 419 were obtained by ultra-violet irradiation to develop natto with weaker flavor. The natto manufactured with these mutants did not contain sticky materials at 41 degreesC but turned to be viscous at 43 degreesC on program A of the Automatic Natto Manufacturing Instrument. The optimum growth temperature of KFP 419 and the mutants coincided with that for manufacturing good quality of natto. The effect of oxygen supply on the quality of natto was not clarified by an experiment using a respiramy cup at the bottom of which an air-permeable plastic laminated film was spreaded. As the odor of natto made by both mutants was weak, to characterize the natto, the volatile components of the head space gas of natto were analyzed by GLC. Although the odor of 3-methyl butanoate was smelled by sniffing at the retention time of this component, its peak was too small to determine quantitatively. It was suggested that the characteristics of the flavors of natto manufactured by the mutants were attributable to complicated quantitative ratio of many volatile components. The elastase activities of the natto of both mutants were lower than that of the parent strain when manufactured at 40 degreesC, but were at the same level as the latter when manufactured at 43 degreesC.