Isolation of lactic acid bacteria from plants of the coastal Satoumi regions for use as starter cultures in fermented milk and soymilk production

• One hundred thirty-eight LAB were isolated from five Satoumi regions in Japan.
• Ten LAB were identified as acid (pH 5.0)-tolerant and milk and/or soymilk fermenters.
• Lactococcuslactis Miura-SU2 is considered a desirable milk fermentation starter.
• Lactobacillusplantarum Tennozu-SU1 increased O2- radical scavenging capacity in soymilk.

The Ministry of the Environment, Government of Japan, defines a Satoumi as a coastal area where biological productivity and biodiversity has increased through human intervention. To identify new starter cultures, we isolated and screened lactic acid bacteria (LAB) with acid resistance and lactose-utilising ability from 94 algal or plant samples obtained from five Satoumi regions in Japan. Among the 138 LAB isolates, 10 were identified as acid (pH 5.0)-tolerant and milk and/or soymilk-fermenting LAB. Among these, six isolates were identified as Lactobacillus plantarum, and four were identified as Lactococcus lactis, respectively. Of the selected strains, only two strains, Lc. lactis Miura-SU2 and Lc. lactis Boso-SU1, lowered milk pH and produced curd. Lc. lactis Miura-SU2 imparted a suitable flavour to the fermented milk. All of the 10 selected LAB showed soymilk fermentation capability. In addition, a suitable flavour was imparted to fermented soymilk by Lc. lactis Miura-SU2. Fermentation by Lb. plantarum Tennozu-SU1 clearly increased the superoxide anion radical scavenging capacity of soymilk. These results suggest that Lc. lactis Miura-SU2 and Lb. plantarum Tennozu-SU1 have potential for use as starter cultures and/or functional components for fermented milk and/or soymilk production.