title: Comparison of Cultivable Acetic Acid Bacterial Microbiota in Organic and Conventional Apple Cider Vinegar.
abstract: Organic apple cider vinegar is produced from apples that go through very restricted treatment in orchard. During the first stage of the process, the sugars from apples are fermented by yeasts to cider. The produced ethanol is used as a substrate by acetic acid bacteria in a second separated bioprocess. In both, the organic and conventional apple cider vinegars the ethanol oxidation to acetic acid is initiated by native microbiota that survived alcohol fermentation. We compared the cultivable acetic acid bacterial microbiota in the production of organic and conventional apple cider vinegars from a smoothly running oxidation cycle of a submerged industrial process. In this way we isolated and characterized 96 bacteria from organic and 72 bacteria from conventional apple cider vinegar. Using the restriction analysis of the PCR-amplified 16S-23S rRNA gene ITS regions, we identified four differentHaeIII and five differentHpaII restriction profiles for bacterial isolates from organic apple cider vinegar. Each type of restriction profile was further analyzed by sequence analysis of the 16S-23S rRNA gene ITS regions, resulting in identification of the following species:Acetobacter pasteurianus(71.90%),Acetobacter ghanensis(12.50%),Komagataeibacter oboediens(9.35%) andKomagataeibacter saccharivorans(6.25%). Using the same analytical approach in conventional apple cider vinegar, we identified only two differentHaeIII and two differentHpaII restriction profiles of the 16S‒23S rRNA gene ITS regions, which belong to the speciesAcetobacter pasteurianus(66.70%) andKomagataeibacter oboediens(33.30%). Yeasts that are able to resist 30 g/L of acetic acid were isolated from the acetic acid production phase and further identified by sequence analysis of the ITS1-5.8S rDNA‒ITS2 region asCandida ethanolica,Pichia membranifaciensandSaccharomycodes ludwigii. This study has shown for the first time that the bacterial microbiota for the industrial production of organic apple cider vinegar is clearly more heterogeneous than the bacterial microbiota for the industrial production of conventional apple cider vinegar. Further chemical analysis should reveal if a difference in microbiota composition influences the quality of different types of apple cider vinegar.
authors.affiliation: Department of Biology, Faculty of Natural Sciences and Mathematics, University of Maribor, Koroška cesta 160, SI-2000 Maribor, Slovenia.
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Štornik
authors.affiliation: Department of Biology, Faculty of Natural Sciences and Mathematics, University of Maribor, Koroška cesta 160, SI-2000 Maribor, Slovenia.
authors.forename: Barbara
authors.initials: B
authors.lastname: Skok
authors.affiliation: Department of Biology, Faculty of Natural Sciences and Mathematics, University of Maribor, Koroška cesta 160, SI-2000 Maribor, Slovenia; Faculty of Chemistry and Chemical Engineering, University of Maribor, Smetanova ulica 17, SI-2000 Maribor, Slovenia.
authors.forename: Janja
authors.initials: J
authors.lastname: Trček
keywords: Acetobacter; Gluconacetobacter; Komagataeibacter; microbiota; organic and conventional apple cider vinegar