NATTO BACTERIUM CAPABLE OF PRODUCING REDUCED AMOUNT OF AMMONIA, METHOD FOR PRODUCTION OF NATTO USING THE NATTO BACTERIUM, AND NATTO

摘要

[PROBLEMS] To grow or develop a Natto bacterium which can reduce the amount of ammonia which is usually produced in a Natto product in a large quantity and rapidly during the course of distribution of the Natto product under high temperature conditions, and to provide a method for producing a Natto which can stay flesh, causes no re-fermentation, produces ammonia at a low concentration, and has no smell of ammonia by using the Natto bacterium. [MEANS FOR SOLVING PROBLEMS] Disclosed is a Natto bacterium which is reduced in the ability of utilizing urea and the ability of utilization of proline. Specifically, the Natto bacterium has an urea utilization rate of 15% or less and a proline utilization rate of 5% or less. Also disclosed is a Natto bacterium having the deletion of an urease gene and a glutamate dehydrogenase gene and therefore having the decrease or loss of the activities of an urease and a glutamate dehydrogenase. Specifically, the Natto bacterium has an urease activity of 40 units/mg protein or less and a glutamate dehydrogenase activity of 140 units/mg protein or less. For example, a Natto having an ammonia concentration of less than 40 ppm can be produced by using each of the Natto bacteria.