The symbiosis among, and the storage stabilities of, starter lactic acid bacterial strains in biofilms.

It is unclear whether biofilm production by co-cultured lactic acid bacteria (LAB) reflects symbiosis among the strains or simply storage stability. This study pairwise combinations of Streptococcus thermophilus ST0 and four strains of lactobacilli to measure the growth relationship and the biofilm yield. The results showed that, during co-culture, the four lactobacilli strains promoted the growth of S. thermophilus ST0 (P < 0.05), and that S. thermophilus ST0 promoted the growth of Lactobacillus delbrueckii subsp. Bulgaricus LD1 and Lactobacillus helveticus LH3 (P < 0.05), but inhibited the growth of Lactobacillus kefiranofaciens LK2 (P < 0.05), and exerted no obvious effect on the growth of Lactobacillus paracasei LP4 compared with strain alone. In terms of the amount of biofilm formed, significantly more was produced by mixed species during the co-cultivation process than by a single strain (P < 0.05), regardless of whether there was a symbiotic relationship among the strains, indicating that biofilm formation by co-cultured strains is not necessarily related to symbiosis among the strains. During the storage of milk fermented by strains co-cultured at 4 °C, the biofilm was inhibited and viable cell numbers were greatly reduced. Biofilm formation slowed the decline in viable cell numbers (P < 0.05). • Biofilm yield of mixed strains was higher than the single when they were co-cultured. • There was no correlation between biofilm yield and symbiosis of co-cultured strains. • LAB biofilm can resist acidic and maintain the storage stability of fermented milk. [ABSTRACT FROM AUTHOR]