Isolation and characterization of new Lactobacilli strains with high level acetaldehyde production, from traditional fermented milk, in different provinces of Iran, are reported. In this study, a total of 112 local dairy products such as yoghurt and doogh were collected from four provinces in the west of Iran, namely Kordestan, Kermanshah, Ilam and Lorestan. Ninety three isolates with extensive diverse phenotypic and biochemical characteristics were identified. These isolates were screened for productions of acetaldehyde during fermentation of skim milk. 67 isolate were positive for acetaldehyde production. Two strains (KR43 and IL121) with the highest acetaldehyde production were further characterized by amplification and sequencing of 16S rRNA genes and their phylogenetic trees were constructed. The results showed that the two strains were similar to Lactobacillus fermentum. 2-dimensional electrophoresis analysis was used to investigate the proteome of the cytosolic fraction extracted from stationary phase cells of the KR43 strain. Also some spots of KR43 strain were analyzed by MS/MS subunits of acetoin dehydrogenase involved in the production of acetaldehyde from acetoin, which has not been reported in Lactobacilli yet. To our knowledge, this is the first report inLactobacilli.
Key words: Acetaldehyde production, acetoin dehydrogenase, Lactobacillus, Iran, proteomics, fermented foods, dairy products
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