title: Biodiversity of refrigerated raw milk microbiota and their enzymatic spoilage potential.
abstract: The refrigerated storage of raw milk selects for psychrotolerant microorganisms, many of which produce peptidases and lipases. Some of these enzymes are heat resistant and are not sufficiently inactivated by pasteurisation or even ultra-high temperature (UHT) treatment. In the current study, 20 different raw cow's milk samples from single farms and dairy bulk tanks were analysed close to delivery to the dairies or close to processing in the dairy for their cultivable microbiota as well as the lipolytic and proteolytic potential of the isolated microorganisms. Altogether, 2906 isolates have been identified and assigned to 169 species and 61 genera. Pseudomonas, Lactococcus and Acinetobacter were the most abundant genera making up 62% of all isolates, whereas 46 genera had an abundance of <1% and represent only 6.6%. Of all isolates, 18% belong to hitherto unknown species, indicating that a large fraction of the milk microbiota is still unexplored. The potential of the isolates to produce lipases or peptidases followed in many cases a genus or group specific pattern. All isolates identified as members of the genus Pseudomonas exhibited mainly lipolytic and proteolytic activity or solely proteolytic activity. On the other hand, nearly all isolates of the genus Acinetobacter were lipolytic but not proteolytic. Only 37% of all tested lactic acid bacteria (LAB) showed enzymatic activity at 6 °C and the type of activity was proteolytic in 97% of these cases.
authors.affiliation: Lehrstuhl für Mikrobielle Ökologie, Zentralinstitut für Ernährungs- und Lebensmittelforschung (ZIEL), Wissenschaftszentrum Weihenstephan, Technische Universität München, Weihenstephaner Berg 3, 85354 Freising, Germany.
authors.forename: Mario
authors.initials: M
authors.lastname: von Neubeck
authors.affiliation: University of Hohenheim, Institute of Food Science and Biotechnology, Department of Biotechnology and Enzyme Science, Garbenstr. 25, 70599 Stuttgart, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Baur
authors.affiliation: University of Hohenheim, Institute of Food Science and Biotechnology, Department of Biotechnology and Enzyme Science, Garbenstr. 25, 70599 Stuttgart, Germany.
authors.forename: Manuel
authors.initials: M
authors.lastname: Krewinkel
authors.affiliation: University of Hohenheim, Institute of Food Science and Biotechnology, Department of Soft Matter Science and Dairy Technology, Garbenstrasse 21, 70599 Stuttgart, Germany.
authors.forename: Marina
authors.initials: M
authors.lastname: Stoeckel
authors.affiliation: University of Hohenheim, Institute of Food Science and Biotechnology, Department of Biotechnology and Enzyme Science, Garbenstr. 25, 70599 Stuttgart, Germany.
authors.forename: Bertolt
authors.initials: B
authors.lastname: Kranz
authors.affiliation: University of Hohenheim, Institute of Food Science and Biotechnology, Department of Biotechnology and Enzyme Science, Garbenstr. 25, 70599 Stuttgart, Germany.
authors.forename: Timo
authors.initials: T
authors.lastname: Stressler
authors.affiliation: University of Hohenheim, Institute of Food Science and Biotechnology, Department of Biotechnology and Enzyme Science, Garbenstr. 25, 70599 Stuttgart, Germany.
authors.forename: Lutz
authors.initials: L
authors.lastname: Fischer
authors.affiliation: University of Hohenheim, Institute of Food Science and Biotechnology, Department of Soft Matter Science and Dairy Technology, Garbenstrasse 21, 70599 Stuttgart, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Hinrichs
authors.affiliation: Lehrstuhl für Mikrobielle Ökologie, Zentralinstitut für Ernährungs- und Lebensmittelforschung (ZIEL), Wissenschaftszentrum Weihenstephan, Technische Universität München, Weihenstephaner Berg 3, 85354 Freising, Germany.
authors.forename: Siegfried
authors.initials: S
authors.lastname: Scherer
authors.affiliation: Lehrstuhl für Mikrobielle Ökologie, Zentralinstitut für Ernährungs- und Lebensmittelforschung (ZIEL), Wissenschaftszentrum Weihenstephan, Technische Universität München, Weihenstephaner Berg 3, 85354 Freising, Germany. Electronic address: mareike.wenning@wzw.tum.de.
authors.forename: Mareike
authors.initials: M
authors.lastname: Wenning
mesh_terms: D000818:Animals; D001419:Bacteria / Q000145:classification / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D044822:Biodiversity; D002417:Cattle; D005260:Female; D008049:Lipase / Q000235:genetics / Q000378:metabolism; D064307:Microbiota; D008892:Milk / Q000737:chemistry / Q000382:microbiology*; D011549:Pseudomonas / Q000302:isolation & purification
chemical_list: D001426:Bacterial Proteins; D008049:Lipase
keywords: Enzyme activity; Lipase; Microbiota; Peptidase; Pseudomonas; Raw milk