title: Bacterial Ecology of Fermented Cucumber Rising pH Spoilage as Determined by Nonculture-Based Methods.
abstract: Fermented cucumber spoilage (FCS) characterized by rising pH and the appearance of manure- and cheese-like aromas is a challenge of significant economical impact for the pickling industry. Previous culture-based studies identified the yeasts Pichia manshurica and Issatchenkia occidentalis, 4 Gram-positive bacteria, Lactobacillus buchneri, Lactobacillus parrafaraginis, Clostridium sp., and Propionibacterium and 1 Gram-negative genus, Pectinatus, as relevant in various stages of FCS given their ability to metabolize lactic acid. It was the objective of this study to augment the current knowledge of FCS using culture-independent methods to microbiologically characterize commercial spoilage samples. Ion Torrent data and 16S rRNA cloning library analyses of samples collected from commercial fermentation tanks confirmed the presence of L. rapi and L. buchneri and revealed the presence of additional species involved in the development of FCS such as Lactobacillus namurensis, Lactobacillus acetotolerans, Lactobacillus panis, Acetobacter peroxydans, Acetobacter aceti, and Acetobacter pasteurianus at pH below 3.4. The culture-independent analyses also revealed the presence of species of Veillonella and Dialister in spoilage samples with pH above 4.0 and confirmed the presence of Pectinatus spp. during lactic acid degradation at the higher pH. Acetobacter spp. were successfully isolated from commercial samples collected from tanks subjected to air purging by plating on Mannitol Yeast Peptone agar. In contrast, Lactobacillus spp. were primarily identified in samples of FCS collected from tanks not subjected to air purging for more than 4 mo. Thus, it is speculated that oxygen availability may be a determining factor in the initiation of spoilage and the leading microbiota.
authors.affiliation: the Dept. of Food, Bioprocessing, and Nutrition Sciences, North Carolina State Univ, Raleigh, NC, 27695, U.S.A.|the Dept. of Food Biotechnology, Inst. de la Grasa, CSIC, Univ. Campus Pablo de Olavide, Building 46, Seville, 41013, Spain.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Medina
authors.affiliation: the USDA-Agriculture Research Service, SAA, Food Science Research Unit, 322 Schaub Hall-NCSU, Raleigh, NC, 27695, U.S.A.
authors.forename: Ilenys M
authors.initials: IM
authors.lastname: Pérez-Díaz
authors.affiliation: the USDA-Agriculture Research Service, SAA, Food Science Research Unit, 322 Schaub Hall-NCSU, Raleigh, NC, 27695, U.S.A.
authors.forename: Fred
authors.initials: F
authors.lastname: Breidt
authors.affiliation: the USDA-Agriculture Research Service, SAA, Food Science Research Unit, 322 Schaub Hall-NCSU, Raleigh, NC, 27695, U.S.A.
authors.forename: Janet
authors.initials: J
authors.lastname: Hayes
authors.affiliation: Dept. of Chemical Enngineering and Bioprocesses, Pontificia Universidad Católica de Chile, Ave, Vicuna Mackena 4860, Macul, 7820436, Santiago, Chile.
authors.forename: Wendy
authors.initials: W
authors.lastname: Franco
authors.affiliation: the Microbiome Core Facility, Dept. of Cell Biology and Physiology, School of Medicine, Univ. of North Carolina, Chapell Hill, NC, 27599, U.S.A.
authors.forename: Natasha
authors.initials: N
authors.lastname: Butz
authors.affiliation: the Microbiome Core Facility, Dept. of Cell Biology and Physiology, School of Medicine, Univ. of North Carolina, Chapell Hill, NC, 27599, U.S.A.
authors.forename: María Andrea
authors.initials: MA
authors.lastname: Azcarate-Peril
mesh_terms: D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D018553:Cucumis sativus / Q000737:chemistry / Q000382:microbiology*; D005285:Fermentation; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000378:metabolism; D015003:Yeasts / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D019344:Lactic Acid
keywords: acetic acid bacteria; cucumbers; fermented vegetables