Genetic Organization of the Operon Affects the Proteolytic Potential of Species in Milk.

Psychrotolerant species are a main cause of proteolytic spoilage of ultra-high temperature (UHT) milk products due to the secretion of the heat-resistant metallopeptidase AprX, which is encoded by the first gene of the operon. While the proteolytic property has been characterized for many different isolates, the underlying gene organization was only described for a few strains so far. In this study, the phylogenomic analysis of 185 type strains revealed that the presence of is strongly associated to a monophylum composed of 81 species, of which 83% carried the locus.

gen. nov., sp. nov., a novel bacterium of the family isolated from raw milk and dairy products and reclassification of as comb. nov.

Eight facultatively anaerobic rod-shaped bacteria were isolated from raw milk and two other dairy products. Results of phylogenetic analyses based on 16S rRNA gene sequences showed that the isolates are placed in a distinct lineage within the family with and as the closest relatives (94.6 and 93.

Pseudomonas lactis sp. nov. and Pseudomonas paralactis sp. nov., isolated from bovine raw milk.

Five strains, designated WS 4672T, WS 4998, WS 4992T, WS 4997 and WS 5000, isolated from bovine raw milk formed two individual groups in a phylogenetic analysis. The most similar species on the basis of 16S rRNA gene sequences were Pseudomonas azotoformans IAM 1603T, Pseudomonas gessardii CIP 105469T and Pseudomonas libanensis CIP 105460T showing 99.7-99.

Biodiversity of refrigerated raw milk microbiota and their enzymatic spoilage potential.

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.