H. Takemura et al., Breeding of branched short-chain fatty acids non-producing natto bacteria and its application to production of natto with light smells, J JPN SOC F, 47(10), 2000, pp. 773-779
Citations number
10
Categorie Soggetti
Food Science/Nutrition
Journal title
JOURNAL OF THE JAPANESE SOCIETY FOR FOOD SCIENCE AND TECHNOLOGY-NIPPON SHOKUHIN KAGAKU KOGAKU KAISHI
Natto contains branched short-chain fatty acids (BCFAS), such as isobutyric
acid, isovaleric acid, and 2-methylbutyric acid. These BCFAS have unpleasa
nt smell. To produce light-smelling natto, we tried to develop BCFAS non-pr
oducing natto bacteria. BCFAS are presumed to be synthesized from branched
amino acids, such as valine, leucine, and isoleucine. Therefore we construc
ted mutant strains, yqiT1 and ywaA1, which lack leucine dehyrogenase (LDH)
and branched-chain amino acid aminotransferase by insertion mutation, respe
ctively. YqiT1 produced much smaller amount of BCFAS than parent strain. Wh
ile, ywaA1 produced BCFAS as much as parent strain. From this result, we co
ncluded that LDH catalyzes the first step of the BCFAS biosynthesis pathway
. Next we deleted the LDH gene of O-2 strain by means of homologous recombi
nation and transduction. Natto made by the use of the mutant strain, B2, wh
ich had a deletion in the LDH gene, contained only 0.7 mg BCFAS/100 g, whil
e natto made by the use of the parent strain contained 70.7 mg BCFAS/100 g.
The natto fermented by B2 strain was valued highly as a light-smelling nat
to by sensary evaluation. Finally, we obtained the LDH-defective mutants by
chemical mutagenesis to utilize in commercial production of natto. The mut
ants produced little BCFAS like B2, and the natto fermented by the mutants
had lighter smells.