title: Research on some factors influencing acid and exopolysaccharide produced by dairy propionibacterium strains isolated from traditional homemade Turkish cheeses.
abstract: In this study, a total of 32 isolated strains and 5 reference strains of dairy propionibacteria were analyzed for acid and exopolysaccharide (EPS) production in skim milk and yeast extract-lactate broth (YEL) media in order to investigate the physiological background and preservative  role of acid and EPS. The effects of final culture pH and optical density on acid and EPS production were also determined. On average, all strains produced more acid and reached lower final pH values in skim milk than in YEL medium. While the correlations obtained between the acid produced  by propionibacterium strains and their final culture pH in skim milk medium were significant (P < 0.01), no correlations were found between optical density, final pH, and produced acid in YEL medium. Sixteen isolated and five reference strains of propionibacteria were tested further  for the ability to produce propionic and acetic acids. On average, Propionibacterium freudenreichii subsp. shermanii and P. freudenreichii subsp. freudenreichii strains produced higher amounts of propionic and acetic acids than did Propionibacterium jensenii  in YEL medium. The acid produced by these strains may be used as a preservative in the food industry for replacement or reduction of the increasing use of chemical additives. The EPS production by propionibacterium strains during growth in YEL medium was 72 to 168 mg/liter, while in skim milk  it was 94 to 359 mg/liter. The monomer compositions of the EPSs formed by the six selected dairy propionibacteria strains were analyzed. The EPSs may have applications as food grade additives and viscosity-stabilizing agents.
authors.affiliation: University of Aksaray, Faculty of Science and Arts, Department of Biotechnology and Molecular Biology, 68100, Aksaray, Turkey. derya_onal@yahoo.com
authors.forename: Derya Onal
authors.initials: DO
authors.lastname: Darilmaz
authors.forename: Yesim
authors.initials: Y
authors.lastname: Gumustekin
mesh_terms: D000085:Acetates / Q000032:analysis / Q000494:pharmacology; D000143:Acids / Q000032:analysis* / Q000494:pharmacology; D000818:Animals; D002611:Cheese / Q000382:microbiology*; D003257:Consumer Product Safety; D005516:Food Microbiology; D005520:Food Preservatives / Q000032:analysis* / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008892:Milk / Q000737:chemistry / Q000382:microbiology; D011135:Polysaccharides, Bacterial / Q000032:analysis*; D011422:Propionates / Q000032:analysis / Q000494:pharmacology; D011424:Propionibacterium / Q000378:metabolism*; D014421:Turkey
chemical_list: D000085:Acetates; D000143:Acids; D005520:Food Preservatives; D011135:Polysaccharides, Bacterial; D011422:Propionates; C029658:propionic acid