Biochemical characterization and technological properties of predominant Lactobacilli isolated from East-Azarbaijan sourdoughs (Iran)

Seventeen traditional sourdough samples were collected from the Northern regions in East-Azarbaijan province of Iran. The pH and total titratable acidity (TTA) values of the sourdoughs varied from 3.71-4.07 and 15.2-26.8 ml, respectively. A total of 50 Lactobacillus strains were isolated from the sourdoughs and identified by biochemical methods. Of the isolates, 74% were identified as L. plantarum and L. curvatus or L. casei subsp. rhamnosus, 10% as L. morinus or L. paralimentarius and 4% as L. sake or L. bavaricus and L. casei subsp. Casei. Three isolates from the main groups were selected and identified using 16S rRNA gene sequencing. The results of gene sequencing revealed the isolates as L. plantarum, L. curvatus and L. paralimentarius. All three Lactobacillus strains produced exopolysaccharide from sucrose in MRS broth medium and also showed proteolytic activity. Lactobacillus curvatus had weak proteolytic activity compared to other strains. The strains showed some differences in acidification properties both in MRS broth and sourdough fermentation. All the strains had good acidifying activity in sourdough fermentation and were able to reduce the pH to less than 4 during 9-12 h incubation at 30°C.