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Subject: search.filters.subject.Geobacillus stearothermophilus

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    Novel hyperthermoacidic archaeal enzymes for removal of thermophilic biofilms from stainless steel
    (Oxford University Press on behalf of Applied Microbiology International, 2023-06) Nam Y; Barnebey A; Kim HK; Yannone SM; Flint S
    AIMS: To test the efficacy of novel hot/acid hyperthermoacidic enzyme treatments on the removal of thermophilic spore-forming biofilms from stainless steel surfaces. METHODS AND RESULTS: The present study measured the efficacy of hyperthermoacidic enzymes (protease, amylase, and endoglucanase) that are optimally active at low pH (≈3.0) and high temperatures (≈80°C) at removing thermophilic bacilli biofilms from stainless steel (SS) surfaces. Plate counts, spore counts, impedance microbiology, as well as epifluorescence microscopy, and scanning electron microscopy (SEM) were used to evaluate the cleaning and sanitation of biofilms grown in a continuous flow biofilm reactor. Previously unavailable hyperthermoacidic amylase, protease, and the combination of amylase and protease were tested on Anoxybacillus flavithermus and Bacillus licheniformis, and endoglucanase was tested on Geobacillus stearothermophilus. In all cases, the heated acidic enzymatic treatments significantly reduced biofilm cells and their sheltering extracellular polymeric substances (EPS). CONCLUSIONS: Hyperthermoacidic enzymes and the associated heated acid conditions are effective at removing biofilms of thermophilic bacteria from SS surfaces that contaminate dairy plants.
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    Characterisation of dairy strains of Geobacillus stearothermophilus and a genomics insight into its growth and survival during dairy manufacture : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Microbiology at Massey University, Palmerston North, New Zealand
    (Massey University, 2016) Burgess, Sara
    The thermophilic bacilli, such as G. stearothermophilus, are an important group of contaminants in the dairy industry. Although these bacilli are generally not pathogenic, their presence in dairy products is an indicator of poor hygiene and high numbers are unacceptable to customers. In addition, their growth may result in milk product defects caused by the production of acids or enzymes, potentially leding to off-flavours. These bacteria are able to grow in sections of dairy manufacturing plants where temperatures reach 40 – 65 °C. Furthermore, because they are spore formers, they are difficult to eliminate. In addition, they exhibit a fast growth rate and tend to readily form biofilms. Many strategies have been tested to prevent the formation of thermophilic bacilli biofilms in dairy manufacture, but with limited success. This is, in part, because little is known about the diversity of strains found in dairy manufacture, the structure of thermophilic bacilli biofilms and how these bacteria have adapted to grow in a dairy environment. In Chapters 2 and 3, phenotypic approaches were taken to understand the diversity of strains within a manufacturing plant. Specifically in Chapter 2, strains of the most dominant thermphilic bacilli, G. stearothermophilus, were isolated from the surface of various locations within the evaporator section and ten strains were evaluated for different phenotypic characteristics. Biochemical profiling, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and fatty profiling demonstrated that the population was diverse. In Chapter 3, it was shown that the same ten strains varied in their ability to form biofilms and produce spores. Three strains of G. stearothermophilus, A1, P3 and D1, were selected for further analysis. SEM demonstrated that there were differences in biofilm morphologies between the three strains, particularly D1 versus the other two strains, A1 and P3. In Chapters 4, 5 and 6 a comparative genomics approach was taken to determine how these bacteria are able to grow and survive within a dairy manufacturing environment, as well as how they differ from other strains of Geobacillus. In Chapter 4 draft genome sequences were generated for three strains of G.stearothermophilus. Identification of a putative lactose operon in the three dairy strains provided evidence of dairy adaptation. In Chapter 5 a phylogenomics approach was taken to resolve relationships within the Geobacillus genus and to identify differences within the G. stearothermophilus group itself. Finally in Chapter 6 comparison with the model organism B. subtilis, gave a genomics insight into the potential mechanisms of sporulation for Geobacillus spp.