Surface characteristics of an adhesive thermophilic spore-forming Bacillus, isolated from milk powder : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand

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dc.contributor.authorPalmer, Jon Stuart
dc.date.accessioned2010-06-20T23:15:01Z
dc.date.availableNO_RESTRICTIONen_US
dc.date.available2010-06-20T23:15:01Z
dc.date.issued2008
dc.description.abstractThe growth of thermophiles during the manufacture of milk powder leads to a progressive increase in the number of thermophilic bacteria contaminating the final product. The limited residence time of the milk in the plant during milk powder manufacture and the concentration effect of converting milk into milk powder cannot explain the number of thermophiles found in the final product. This suggests that thermophiles are attaching to the large surface area of stainless steel found within a milk powder plant and then growing and developing into biofilms, with individual cells and/or biofilm fragments sloughing off into the product line and thus contaminating the final product. The aim of the present study was to investigate the attachment mechanisms that enable the thermophile Anoxybacillus flavithermus (B 1 2) to attach to stainless steel surfaces. Passing a B 1 2 culture through a column of stainless steel chips, collecting the first cells to pass through, re-culturing and repeating the process six times, resulted in the isolation of a mutant, labelled X7, with lO-fold reduced ability to attach to stainless steel as well as a reduced ability to attach to plastic and glass. A comparison of bacterial cell surface properties indicated that X7 was less hydrophobic than its parental strain B 1 2 . Cell surface charge measurements also suggest that X7 has less net negative surface charge. Disruption of extracellular polysaccharides and DNA appeared to have no effect on the attachment process. Removal of surface proteins caused a reduction in attachment of B 1 2 and X7 as well as a reduction in surface hydrophobicity suggesting surface protein involvement in both. Analysis by two-dimensional gel electrophoresis of lysozyme/mutanolysin extracted surface proteins revealed two proteins expressed at reduced levels in X 7 compared with B 1 2 . One protein was identified by mass spectrometry as the cytoplasmic enzyme Formate acetyltransferase. The role of Formate acetyltransferase and the second unidentified protein on the attachment process of Anoxybacillus flavithermus remains unclear.en_US
dc.identifier.urihttp://hdl.handle.net/10179/1384
dc.language.isoenen_US
dc.publisherMassey Universityen_US
dc.rightsThe Authoren_US
dc.subjectMilk powder manufactureen_US
dc.subjectBiofilmen_US
dc.subjectAnoxybacillus flavithermusen_US
dc.subject.otherFields of Research::290000 Engineering and Technology::290100 Industrial Biotechnology and Food Sciences::290101 Fermentation, biotechnology and industrial microbiologyen_US
dc.titleSurface characteristics of an adhesive thermophilic spore-forming Bacillus, isolated from milk powder : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealanden_US
dc.typeThesisen_US
massey.contributor.authorPalmer, Jon Stuart
thesis.degree.disciplineFood Technologyen_US
thesis.degree.grantorMassey Universityen_US
thesis.degree.levelDoctoralen_US
thesis.degree.levelDoctoralen
thesis.degree.nameDoctor of Philosophy (Ph.D.)en_US
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