Browsing by Author "Lindsay D"

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    Addition of selected cereal grains as non-dairy ingredients to dairy products: A microbiological risk assessment approach
    (Elsevier Ltd., 2024-08-01) Fatima F; Pramularsih I; Kyere EO; Lindsay D; Abernethy G; Laing S; Flint S
    The addition of cereal grains to dairy products in the dairy industry has the potential to contaminate final products with pathogenic and spoilage microorganisms. In this study, the microbial risks involved in the addition of cereal grains to dairy products with low, intermediate, and high-water activity/moisture content were assessed using a semi-quantitative risk assessment method. The results showed that the most critical microbiological hazard in the selected cereal grains is Bacillus cereus (B. cereus) due to its ability to form spores and persist in cereal grains. The addition of cereal grains to dairy products with high water activity/moisture content such as liquid breakfast products were found to pose the highest theoretical risk, and processing mitigations, such as UHT, would need to be implemented. The results of this study have identified some knowledge gaps in conducting risk assessments and have also provided background information about the microbial risks involved in the addition of cereal grains to dairy products.
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    Draft Genome Sequences of Three Strains of Geobacillus stearothermophilus Isolated from a Milk Powder Manufacturing Plant.
    (15/10/2015) Burgess SA; Cox MP; Flint SH; Lindsay D; Biggs PJ
    Three strains of Geobacillus stearothermophilus (designated A1, P3, and D1) were isolated from a New Zealand milk powder manufacturing plant. Here, we describe their draft genome sequences. This information provided the first genomic insights into the nature of G. stearothermophilus strains present in the milk powder manufacturing environment.
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    Insights into the Geobacillus stearothermophilus species based on phylogenomic principles.
    (26/06/2017) Burgess SA; Flint SH; Lindsay D; Cox MP; Biggs PJ
    BACKGROUND: The genus Geobacillus comprises bacteria that are Gram positive, thermophilic spore-formers, which are found in a variety of environments from hot-springs, cool soils, to food manufacturing plants, including dairy manufacturing plants. Despite considerable interest in the use of Geobacillus spp. for biotechnological applications, the taxonomy of this genus is unclear, in part because of differences in DNA-DNA hybridization (DDH) similarity values between studies. In addition, it is also difficult to use phenotypic characteristics to define a bacterial species. For example, G. stearothermophilus was traditionally defined as a species that does not utilise lactose, but the ability of dairy strains of G. stearothermophilus to use lactose has now been well established. RESULTS: This study compared the genome sequences of 63 Geobacillus isolates and showed that based on two different genomic approaches (core genome comparisons and average nucleotide identity) the Geobacillus genus could be divided into sixteen taxa for those Geobacillus strains that have genome sequences available thus far. In addition, using Geobacillus stearothermophilus as an example, we show that inclusion of the accessory genome, as well as phenotypic characteristics, is not suitable for defining this species. For example, this is the first study to provide evidence of dairy adaptation in G. stearothermophilus - a phenotypic feature not typically considered standard in this species - by identifying the presence of a putative lac operon in four dairy strains. CONCLUSIONS: The traditional polyphasic approach of combining both genotypic and phenotypic characteristics to define a bacterial species could not be used for G. stearothermophilus where many phenotypic characteristics vary within this taxon. Further evidence of this discordant use of phenotypic traits was provided by analysis of the accessory genome, where the dairy strains contained a putative lac operon. Based on the findings from this study, we recommend that novel bacterial species should be defined using a core genome approach.