Induction of superoxide anion radical scavenging capacity in Japanese white radish juice and milk by Lactobacillus plantarum isolated from aji-narezushi and kaburazushi

Aji-narezushi (salted and fermented horse mackerel with rice) and kaburazushi (salted and fermented turnip with yellowtail and malted rice) are traditional lactic acid-fermented foods in Japan. In this study, we screened lactose utilizable, acidophilic and antioxidative lactic acid bacteria (LAB) from aji-narezushi and kaburazushi for use as a starter of various fermented foods, as well as for probiotics. Of the 177 LAB isolated strains, 57 strains fermented lactose and among these, 28 grew in MRS broth adjusted to pH 4.5. All of these 28 strains were lactobacilli and produced lactic acid in 50% Japanese white radish (daikon) juice at 15 °C. The fermented daikon   juice increased the superoxide radical (O2-) scavenging capacity, but did not change clearly the DPPH− scavenging capacity and ferrous reducing power. The O2- scavenging activity component was fractionated to <5 kDa by ultrafiltration. Three selected strains (two from aji-narezushi and three from kaburazushi) that showed high scavenging activity are identified to Lactobacillus plantarum by 16S rRNA sequence identity and carbohydrate utilization test (API-CHL50). These L. plantarum strains could ferment milk at 42 °C, like yogurt starters, and the O2- scavenging activity was increased by fermentation. These results suggest that the L. plantarum strains can be used as profitable starter organisms and probiotics.