Properties of Leuconostoc lactis isolated from traditional fermented rice beverages as a starter

Abstract

The health benefits of traditional fermented rice beverages have attracted considerable attention. “Miki” from the Amami Ohshima island is made from spontaneously fermented rice saccharified with sweet potato β-amylase. Leuconostoc lactis is the dominant species isolated from Miki. In this study, we aimed to clarify the role of indigenous Ln. lactis in fermented rice beverages by determining the antimicrobial activity, exopolysaccharide (EPS) production capacity, and Miki fermentation properties. Among the isolates, Ln. lactis Miki-A3 showed superior anti-listerial activity in the agar overlay method and EPS production with antioxidant capacity (O₂^- radical scavenging and Fe-reducing power) compared with those of the type strain. The antibiotic resistance and related genes of Miki-A3 were similar to those of the type strain. The positions and orders of EPS-related genes differed between the two strains. In the Miki fermentation model, Miki-A3 fermented well at 30 ℃ and decreased Listeria monocytogenes (Lm) count from 5 log to below the detection limit (< 3.3 log CFU/mL) in 24 h. In the fermented Miki stored at 10 ℃, the Lm count immediately decreased. These results indicate that Miki-A3 is a promising starter for rice-fermented beverages in terms of health functionality and hygiene.