Yamamoto Eri, Watanabe Reiko, Koizumi Akiko, Ishida Tatsuya, Kimura Katsunori
Food Microbiology Research Laboratories R&D Division, Meiji Co., Ltd., 1-29-1 Nanakuni, Hachioji, Tokyo 192-0919, Japan.
Food Development Laboratories R&D Division, Meiji Co., Ltd., 1-29-1 Nanakuni, Hachioji, Tokyo 192-0919, Japan.
Biosci Microbiota Food Health. 2020;39(3):169-174. doi: 10.12938/bmfh.2019-052. Epub 2020 Mar 20.
is widely used for producing fermented dairy products such as yogurt and cheese. Some strains possessing the cell-wall protease PrtS show high proteolytic activity and fast acidification properties, which are very useful in industrial starters. However, few strains possessing the gene have been isolated from the environment. To clarify whether or not strains possessing the gene are present in Japan, we isolated from raw milk collected in Japan from 2011 to 2017 and investigated the strains for the presence of by PCR. A total of 172 strains were isolated, and 59 strains were confirmed to possess . We measured fermentation times of 59 -positive strains in skim milk broth and found that 53 strains showed fast acidification properties, finishing fermentation within 10 hr. However, the remaining 6 -positive strains showed slow acidification properties, and they had several amino acid mutations in PrtS compared with fast acidifying LMD-9 and 4F44. These results demonstrate that strains possessing are prevalent in Japan and that some -positive strains could lose their fast acidifying properties through mutations in PrtS.
广泛用于生产发酵乳制品，如酸奶和奶酪。一些具有细胞壁蛋白酶PrtS的菌株表现出高蛋白水解活性和快速酸化特性，这在工业发酵剂中非常有用。然而，从环境中分离出的具有该基因的菌株很少。为了弄清楚日本是否存在具有该基因的菌株，我们从2011年至2017年在日本采集的原料奶中分离出该菌株，并通过PCR检测这些菌株中是否存在该基因。总共分离出172株该菌株，其中59株被证实具有该基因。我们测量了59株阳性菌株在脱脂牛奶肉汤中的发酵时间，发现53株表现出快速酸化特性，在10小时内完成发酵。然而，其余6株阳性菌株表现出缓慢酸化特性，与快速酸化的LMD-9和4F44相比，它们的PrtS中有几个氨基酸突变。这些结果表明，具有该基因的菌株在日本很普遍，并且一些阳性菌株可能通过PrtS中的突变失去其快速酸化特性。
