Seasonal influence on heat-resistant proteolytic capacity of Pseudomonas lundensis and Pseudomonas fragi, predominant milk spoilers isolated from Belgian raw milk samples.
Psychrotolerant bacteria and their heat-resistant proteases play a major role in the spoilage of UHT-processed dairy products. Summer and winter raw milk samples were screened for the presence of such bacteria. One hundred and three proteolytic psychrotolerant bacteria were isolated, characterized by API tests, rep-PCR fingerprint analysis and evaluated for heat-resistant protease production. Twenty-nine strains (representing 79% of the complete collection) were further identified by 16S rRNA gene sequencing, rpoB gene sequencing and DNA-DNA hybridizations. A seasonal inter- and intra-species influence on milk spoilage capacity (e.g. growth rate and/or protease production) was demonstrated. Moreover, this polyphasic approach led to the identification of Pseudomonas fragi and Pseudomonas lundensis (representing 53% of all isolates) as predominant producers of heat-resistant proteases in raw milk. The role of Pseudomonas fluorescens, historically reported as important milk spoiler, could not unequivocally be established. The use of more reliable identification techniques and further revision of the taxonomy of P. fluorescens will probably result in a different perspective on its role in the milk spoilage issue.
Marchand
Sophie
S
Institute for Agricultural and Fisheries Research, Technology and Food Unit (ILVO-T&V), Melle, Belgium. sophie.marchand@ilvo.vlaanderen.be
Heylen
Kim
K
Messens
Winy
W
Coudijzer
Katleen
K
De Vos
Paul
P
Dewettinck
Koen
K
Herman
Lieve
L
De Block
Jan
J
Heyndrickx
Marc
M
D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism*; D001530:Belgium; D016000:Cluster Analysis; D016172:DNA Fingerprinting; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D012321:DNA-Directed RNA Polymerases; D020459:Genes, rRNA; D008892:Milk / Q000382:microbiology*; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D010447:Peptide Hydrolases / Q000378:metabolism*; D010802:Phylogeny; D011549:Pseudomonas / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012621:Seasons; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D012321:DNA-Directed RNA Polymerases; C105078:RNA polymerase beta subunit; D010447:Peptide Hydrolases