A survey of the relationship between functional genes and acetaldehyde production characteristics in Streptococcus...

Streptococcus thermophilus is an important bacterium used in the production of fermented dairy products. Yogurt with good flavor is preferred by consumers; thus, variation in flavor-formation characteristics among isolates is attracting attention. Here, acetaldehyde production characteristics of 30 isolates were evaluated in parallel with genotyping and multilocus sequence typing of key functional genes involved in acetaldehyde production. The results showed that isolates could be divided into 3 phenotypically distinct groups: high-acetaldehyde-yielding isolates (>10 mg/L), medium-acetaldehyde-yielding isolates (5-10 mg/L) and low-acetaldehyde-yielding (<5 mg/L) based on evaluation of acetaldehyde production during yogurt storage. These groups, distinguishable by phenotypic characteristics, were clustered in corresponding groups based on functional gene multilocus sequence typing analysis. Combining functional gene sequence analysis of 30 Strep. thermophilus isolates with phenotypic evaluation of their flavor-related characteristics (specifically acetaldehyde production) demonstrated that groups of isolates established using genotype data analysis corresponded with groups identified based on their phenotypic traits. Interestingly, the 30 isolates of Strep. thermophilus showed significant phylogenetic clustering in acetaldehyde content by functional gene and acetaldehyde content analysis. A corresponding relationship exists between functional gene phylogenetic clustering and acetaldehyde content variation.