title: Enumeration and discrimination of thermophilic bacilli in milk powder

authors: Rückert, Andreas

abstract: A survey of milk powders from eighteen different countries has established that the same cohorts of strains of thermophilic bacilli are the major contaminants regardless of source. In particular, Anoxybacillus flavithermus strain C emerges as the most commonly encountered contaminant especially in powders with a medium- to high thermophile count. Bacillus licheniformis strain F was the next most common contaminant overall which dominated low- to medium count powders. This organism was also the broadest distributed being present in 96% of the milk powders screened. The thermophilic Geobacillus stearothermophilus strain A represented the third most often occurring milk powder isolate. The presence of B. licheniformis strain G, Bacillus subtilis and A. flavithermus strain D as low-level contaminants of milk powder was reconfirmed. 
Methods have been developed for the rapid and efficient extraction of bacteria from milk powder and their enumeration using real-time PCR methodology based on the 16S rRNA gene or the spoOA gene. Further modifications to these methods allow discrimination between live and dead cells and between spores and vegetative cells. The former is important because the majority of vegetative cells in milk powder are dead as a result of processing stresses, yet their DNA remains available for amplification. Limits of detection of these methods for viable cells and spores are less than 1000 thermophiles per gram of milk powder. These methods can yield results within a time period of 90 minutes and thus are amenable to real-time monitoring of factory contamination in situ. 
A range of other methodologies and approaches to detecte and enumerate thermophilic bacilli were investigated but were not regarded as applicable. The use of antibodies raised against thermophilic bacilli did not produce sufficient discrimination between strains and did not allow enumeration of different strains with the same efficiency of detection, and could not differentiate between live and dead cells. DGGE-PCR performed on the highly conserved region of the 16S rRNA gene also exposed the presence of organisms other than thermophilic bacilli in milk powder compromising the resolution of the detection method. RAPD-PCR provided a high discrimination between the strains but was not applicable for the use in a factory setting. 
Overall, the discovery that virtually all milk powders produced internationally and in New Zealand are dominated by thermophilic strains representing four species is a fundamental finding regarding factory-derived contamination. This will have long-term effects on the future operation and design of evaporator lines, and has important economic implications with respect to optimizing day-to-day factory operation and storage of milk powders. In addition, the quantitative real-time PCR assays from this study should allow for a robust control of the drying process during extended run times and thus, are of important economical benefices to milk powder manufacturer.

text: Enumeration and discrimination of thermophilic bacilli in milk powder A survey of milk powders from eighteen different countries has established that the same cohorts of strains of thermophilic bacilli are the major contaminants regardless of source. In particular, Anoxybacillus flavithermus strain C emerges as the most commonly encountered contaminant especially in powders with a medium- to high thermophile count. Bacillus licheniformis strain F was the next most common contaminant overall which dominated low- to medium count powders. This organism was also the broadest distributed being present in 96% of the milk powders screened. The thermophilic Geobacillus stearothermophilus strain A represented the third most often occurring milk powder isolate. The presence of B. licheniformis strain G, Bacillus subtilis and A. flavithermus strain D as low-level contaminants of milk powder was reconfirmed. 
Methods have been developed for the rapid and efficient extraction of bacteria from milk powder and their enumeration using real-time PCR methodology based on the 16S rRNA gene or the spoOA gene. Further modifications to these methods allow discrimination between live and dead cells and between spores and vegetative cells. The former is important because the majority of vegetative cells in milk powder are dead as a result of processing stresses, yet their DNA remains available for amplification. Limits of detection of these methods for viable cells and spores are less than 1000 thermophiles per gram of milk powder. These methods can yield results within a time period of 90 minutes and thus are amenable to real-time monitoring of factory contamination in situ. 
A range of other methodologies and approaches to detecte and enumerate thermophilic bacilli were investigated but were not regarded as applicable. The use of antibodies raised against thermophilic bacilli did not produce sufficient discrimination between strains and did not allow enumeration of different strains with the same efficiency of detection, and could not differentiate between live and dead cells. DGGE-PCR performed on the highly conserved region of the 16S rRNA gene also exposed the presence of organisms other than thermophilic bacilli in milk powder compromising the resolution of the detection method. RAPD-PCR provided a high discrimination between the strains but was not applicable for the use in a factory setting. 
Overall, the discovery that virtually all milk powders produced internationally and in New Zealand are dominated by thermophilic strains representing four species is a fundamental finding regarding factory-derived contamination. This will have long-term effects on the future operation and design of evaporator lines, and has important economic implications with respect to optimizing day-to-day factory operation and storage of milk powders. In addition, the quantitative real-time PCR assays from this study should allow for a robust control of the drying process during extended run times and thus, are of important economical benefices to milk powder manufacturer.

year: 2005

title: Modelling the response of a highly eutrophic lake to reductions in external and internal nutrient loading

authors: Özkundakci, Deniz

subjects: Lake Okaro

abstract: The reduction of macronutrients to levels that limit primary production is often a critical element of mitigating eutrophication and reducing the potential for algal blooms. Lake Okaro has remained highly eutrophic despite an intensive catchment and in-lake restoration programme, including implementation of a constructed wetland, riparian protection, an alum application and application of a modified zeolite mineral (Z2G1) to reduce internal nutrient loading. A one-dimensional process-based ecosystem model (DYRESM-CAEDYM) was used in this study to investigate the need for further nutrient loading reductions of both nitrogen (N) and phosphorus (P). The model was calibrated against field data for a 2-year period and validated over two separate 1-year periods. Model simulations suggest that the trophic status of the lake, measured quantitatively with the Trophic Level Index (TLI), could shift from highly eutrophic to mesotrophic with external and internal loads of both N and P reduced by 75-90%. The magnitude of the nutrient load reductions is indicative of a major challenge in being able to effect transitions across trophic state categories for eutrophic lakes.

text: Modelling the response of a highly eutrophic lake to reductions in external and internal nutrient loading The reduction of macronutrients to levels that limit primary production is often a critical element of mitigating eutrophication and reducing the potential for algal blooms. Lake Okaro has remained highly eutrophic despite an intensive catchment and in-lake restoration programme, including implementation of a constructed wetland, riparian protection, an alum application and application of a modified zeolite mineral (Z2G1) to reduce internal nutrient loading. A one-dimensional process-based ecosystem model (DYRESM-CAEDYM) was used in this study to investigate the need for further nutrient loading reductions of both nitrogen (N) and phosphorus (P). The model was calibrated against field data for a 2-year period and validated over two separate 1-year periods. Model simulations suggest that the trophic status of the lake, measured quantitatively with the Trophic Level Index (TLI), could shift from highly eutrophic to mesotrophic with external and internal loads of both N and P reduced by 75-90%. The magnitude of the nutrient load reductions is indicative of a major challenge in being able to effect transitions across trophic state categories for eutrophic lakes.

year: 2011-06

title: Māori diaspora: Being Māori on the Gold Coast

authors: Henderson, Eve Ngāwaiata

subjects: Māori

abstract: An estimated one in five Māori now live in Australia with the largest concentration on the Gold Coast. My research gives voice to the lived realities of the Māori diaspora and is informed by my own reflections as a first-generation Australian-born Māori and those of my whānau. Through discussion with whānau who either emigrated over to Australia as adults or were born and raised in Australia because of their parents’ emigration, in my thesis I shed light on constructions of identity and notions of belonging for Māori on the Gold Coast living on the traditional land of the Aboriginal and Torres Strait Islander Peoples. 

With an understanding of the entangled complexities on undertaking research on Māori living on the land of another Indigenous Peoples, I utilise both Kaupapa Māori and Indigenous Research paradigms as the foundation for this thesis. Using pūrākau  as method, with a storytelling approach, I had expected to be sitting with my whānau kanohi ki te kanohi, sharing food and laughs in the home. However, Covid-19 put a halt to my desired research approach. Despite this hurdle, I was able to collate and combine our shared stories to express what it is to be Māori on the Gold Coast through the utilisation of online spaces. Through my findings, I demonstrate that Māori on the Gold Coast articulate a range of ways to be Māori with diverse and hopeful views for the future. This challenges dominant Māori scholarship which often excludes and invisibilizes Māori experiences outside of Aotearoa, as if people cease to be Māori once they have left. 

This thesis adds to Indigenous diasporic discussions in communicating the fluidity of Māori identity. I argue that Māori have a connection to Aotearoa that is not necessarily tied physically to the whenua, nor bound to preconceptions and measures of history. Understanding our diaspora is essential for considering future implications for Indigenous solidarity, and for cultural growth and retention.

text: Māori diaspora: Being Māori on the Gold Coast An estimated one in five Māori now live in Australia with the largest concentration on the Gold Coast. My research gives voice to the lived realities of the Māori diaspora and is informed by my own reflections as a first-generation Australian-born Māori and those of my whānau. Through discussion with whānau who either emigrated over to Australia as adults or were born and raised in Australia because of their parents’ emigration, in my thesis I shed light on constructions of identity and notions of belonging for Māori on the Gold Coast living on the traditional land of the Aboriginal and Torres Strait Islander Peoples. 

With an understanding of the entangled complexities on undertaking research on Māori living on the land of another Indigenous Peoples, I utilise both Kaupapa Māori and Indigenous Research paradigms as the foundation for this thesis. Using pūrākau  as method, with a storytelling approach, I had expected to be sitting with my whānau kanohi ki te kanohi, sharing food and laughs in the home. However, Covid-19 put a halt to my desired research approach. Despite this hurdle, I was able to collate and combine our shared stories to express what it is to be Māori on the Gold Coast through the utilisation of online spaces. Through my findings, I demonstrate that Māori on the Gold Coast articulate a range of ways to be Māori with diverse and hopeful views for the future. This challenges dominant Māori scholarship which often excludes and invisibilizes Māori experiences outside of Aotearoa, as if people cease to be Māori once they have left. 

This thesis adds to Indigenous diasporic discussions in communicating the fluidity of Māori identity. I argue that Māori have a connection to Aotearoa that is not necessarily tied physically to the whenua, nor bound to preconceptions and measures of history. Understanding our diaspora is essential for considering future implications for Indigenous solidarity, and for cultural growth and retention.

year: 2021