title: RAPD-based screening for spore-forming bacterial populations in Uruguayan commercial powdered milk.
abstract: The occurrence of spore-forming bacteria in powdered milk is of concern to the dairy industry due to potential deleterious effects including those resulting from proteolytic and lipolytic activities. Twenty-two powdered milk samples representative of spring and summer production obtained from Uruguayan retail stores were analyzed for type and number of thermophilic and spore-forming bacterial species. Bacillus licheniformis isolates were found to be the most prominent milk powder contaminant followed by Anoxybacillus flavithermus representing 71.5 to 84% of the total microflora. Geobacillus stearothermophilus, however, was not found. B. licheniformis strains F and G were both found in this study but strain F was the prevalent isolate representing 98.9% of the total isolates of this species. A. flavithermus isolates corresponded to strain C in accordance with 16S rRNA gene sequence analysis, however, in contrast with other reports, the RAPD profiles showed three characteristic bands at approximately 650, 1000 and 1650 bp, but lacking a band at 1250 bp. A third group of isolates was identified corresponding to members of a Bacillus subtilis group and Bacillus megaterium. Isolates designated B. licheniformis, A. flavithermus, B. megaterium and the B. subtilis group represented 89.1 to 93.6% of those analyzed, and depended on previous heat treatment and incubation temperatures of the plates. The remaining isolates were Bacillus pumilus and unidentified spore-formers.
authors.affiliation: Unidad de Tecnología de Alimentos, Universidad de la República, Montevideo, Uruguay. stellareginensi@gmail.com
authors.forename: Stella M
authors.initials: SM
authors.lastname: Reginensi
authors.forename: Marcela J
authors.initials: MJ
authors.lastname: González
authors.forename: Jorge A
authors.initials: JA
authors.lastname: Olivera
authors.forename: Mariela
authors.initials: M
authors.lastname: Sosa
authors.forename: Pablo
authors.initials: P
authors.lastname: Juliano
authors.forename: Jorge
authors.initials: J
authors.lastname: Bermúdez
mesh_terms: D000818:Animals; D058677:Anoxybacillus / Q000235:genetics / Q000302:isolation & purification*; D001407:Bacillus / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D003611:Dairy Products / Q000382:microbiology*; D005506:Food Contamination / Q000032:analysis*; D001411:Geobacillus stearothermophilus / Q000235:genetics / Q000302:isolation & purification; D019105:Random Amplified Polymorphic DNA Technique / Q000379:methods*; D013171:Spores, Bacterial / Q000235:genetics / Q000302:isolation & purification*