Lactic acid bacteria effective for regulating the growth of contaminant bacteria during the fermentation of Undaria pinnatifida (Phaeophyta)

Lactic acid fermentation of seaweed is a recent topic and quite limited information is available on culture conditions. To know the suitable strains for use as a starter culture for seaweed fermentation, 14 lactic acid bacteria (LAB) strains, including 11 species, were tested in culture conditions prepared with or without salt. A commercial product of Undaria pinnatifida powder was used as a substrate for fermentation without sterilizing. Starter-suitability of the LAB strains was assessed from their predominance after culture. Among the tested strains, Lactobacillus brevis, Lactobacillus plantarum, Lactobacillus casei and Lactobacillus rhamnosus showed high (>90%) predominance in their cultures, while control cultures prepared without inoculation of LAB did not show any detectable growth of acid producing bacteria and spoiled. A total of 102 strains not showing acid producing activity were isolated and characterized from spoiled cultures, and all the isolates were observed as Bacillus strains, including 64 strains (62.7%) and 16 strains (15.7%) of a Bacillus cereus-related and B. fusiformis-related species, respectively. The Undaria substrate before fermentation contained culturable microorganisms at 1.4−3.1 × 102 CFU/g, but the Bacillus cereus-related strain was not a major composition, suggesting a concern of selective growth of the Bacillus cereus-related strain during the spoiled fermentation.