Our Research
Predictive microbiology
A European Union-funded project, co-ordinated by Jane Sutherland at LMET with partners Dr Peggy Braun at the University of Leipzig (LINK), Professor Elisabetta Guerzoni at the University of Bologna (LINK), Dr Jozsef Baranyi at the Institute of Food Research (LINK) and Dr Cristina Moretti at AVI-COOP, resulted in the development of predictive models for spoilage of perishable foods. These models are based not only on microbial growth, but also on metabolic activities of microorganisms resulting in accumulation of volatile organic compounds, leading to organoleptic deterioration of perishable foods. Vandanna Prajapat from LMET was awarded the degree of PhD (2004) for her research on this subject. Data on enzyme synthesis and activity in food spoilage generated at the University of Leipzig (LINK) is being modelled in conjunction with STORM (Statistics Operational and Mathematics Research Centre (LINK) at LMET.
In 1999, Dr J. Sutherland was awarded a grant (€525,000 for 3 years) under Framework 5 of the European Union Research Funding Program to develop, verify and validate predictive models for food spoilage (the "SpoilPred" project). The project, coordinated by this University, included academic partners at the Universities of Leipzig (Professor K. Fehlhaber and Dr P. Braun), Bologna (Professor M.E. Guerzoni) and the Institute of Food Research, UK (Dr J. Baranyi). The Italian poultry company Avi-Coop (Dr C. Moretti) was included as an industrial partner. The aim of the project was to develop an overall food spoilage model, incorporating measurement of accumulated microbial metabolites and proteolytic and lipolytic exo-enzymes synthesised by microorganisms, as well as measuring growth rates of the selected organisms. The significance and novelty of this project was that predictive models for food spoilage were envisaged, rather than simply growth rate models for food spoilage microorganisms. A research student, V. Prajapat, registered at this University , was awarded a PhD in 2004 for her work on developing a predictive model for spoilage by Brochothrix thermosphacta for based on accumulation of 3-methyl butanol. A number of publications have resulted from work on this project and it is intended to put the models on the University website so that they can be accessed by external users.
Work on the enzymatic data generated in the project is continuing in collaboration with STORM at this University.
Work by the MRU on predictive microbiology is reinforced by participation in the e-COMBASE (COMbined dataBASE) project, another EU-funded project, co-ordinated by Dr J. Baranyi at the UK Institute of Food Research. This international database incorporates microbiological growth rate data from throughout the world, but data are included in the database only if they pass stringent quality checks applied by Dr Baranyi's group. All microbiological data generated in the "SpoilPred" project is of a sufficiently high standard for inclusion in the database. The database can be used for prediction of growth of foodborne pathogens and food spoilage organisms, as well as for examination of the raw data.
Since non-thermal decline of microorganisms is not exponential, it is infinitely more difficult to develop a predictive capability for microbial decline (death or survival) than for growth. Current effort in the MRU is directed towards generating systematic death/survival data for foodborne pathogens in conditions of decreasing water activity. Mathematical/statistical techniques for modelling those data are being developed in collaboration with STORM at London Metropolitan University
Other approaches to bioinformatics in the MRU include attempts to solve the so-called "hard to solve" problems in the food industry using specific software such as Crystal Ball and Cubist to identify specific events leading to manifestation of problems.
Survival of foodborne pathogens
The survival of foodborne pathogens in conditions that do not permit growth is of crucial importance to the food industry and to public health and forms a substantial proportion of our research. A Food Standards Agency-funded project managed by Alan Varnam involved collaboration with Dr Peter Cripps at the Faculty of Veterinary Science, University of Liverpool (LINK) to investigate the role of the external surface of eggs in cross-contamination by salmonellae led to the conclusion that retail hens' eggs cannot be guaranteed to be free of salmonellae and could be a vector in the spread of this organism. Pilar Botey-Salo extended this work into an investigation of the molecular aspects of survival of salmonellae on eggs and is currently writing her PhD thesis on this topic.
Current research by MRU in this area includes an investigation of fluctuating water activity on the survival of foodborne pathogens including salmonellae, Listeria monocytogenes and Escherichia coli O157:H7 (non-toxigenic variant)
Probiotics
A grant awarded to Alan Varnam by the Food Standards Agency (LINK) enabled Alan and Claudio Scotti to evaluate claims concerning numbers and types of starter bacteria in fermented probiotic milk products and dried probiotic products, in collaboration with Professor Glen Gibson at the University of Reading (LINK). The research resulted in a method to isolate and identify probiotic microorganisms which is regarded as the "gold standard" for this procedure. The research concluded that, despite claims made on labels of many of these products, probiotic microorganisms are either absent, or present in numbers too low to be of value and mis-labelling of products is common.
Alan Varnam also prepared a literature review, leading to construction of a database on the safety and suitability of Bacillus spp. for use as probiotics in animal nutrition. The database is available for consultation on the Food Standards Agency website (LINK).
Eleheh Sarraf Zadeh is a PhD student working on the probiotic properties of selected Bifidobacterium spp. and lactic acid bacteria, including their resistance to gastric conditions and interaction with foodborne pathgens.
Traditional fermentations
As part of the MRU “Probiotics for Africa” programme (LINK), Brigitte Awamaria in undertaking a PhD project to develop an infant weaning food by nutritional supplementation of traditionally-fermented cassava. Some microorganisms associated with traditional fermentations also have probiotic properties and a Royal Society award enabled a visiting worker, Irene Ouoba from Burkina Faso, to investigate the role of Bacillus spp. in the fermentation of seeds of Hibiscus sabdariffa to form Bikalga, an alkaline fermented food widely consumed insub-Saharan Africa. Two strains of B. subtilis were found to be of high potential as starter cultures for production of bikalga, with activity against foodborne pathogens.
Hanane Goudjil, is investigating the properties of lactic acid bacteria isolated from traditional cheese made by nomads in the Sahara desert from ewes' or goats' milk, with the aim of relating these properties to the development of volatile organic compounds involved in flavour development in the cheese.
The research structure of the MRU is organised within four main interlinked themes:
Theme 1: Predictive microbiology and bioinformatics
Theme 2: Microbial survival
Survival of foodborne pathogens in combinations of environmental conditions that do not permit growth is an extremely important area of microbiology with considerable implications for the food industry. Microbial survival is arguably more important than growth. There is a strong link between research in this theme and that in Theme 1, with respect to data generation for modelling of survival of microoganisms in conditions inimical to growth.
In 2000, Dr A. Varnam and Dr J. Sutherland were awarded a Food Standards Agency grant (£117,000 for 3 years) to evaluate the role of cross-contamination from the external surface of hens' eggs in relation to risk of exposure to salmonella ("SalEggs" project). The project was undertaken in collaboration with Dr P. Cripps of the University of Liverpool Faculty of Veterinary Science. It was found that salmonella would survive on the surface of eggs for at least 3 weeks and could be transferred to hands of egg-handlers and to fibreboard packaging cartons. A research assistant, P. Botey-Salo registered as a PhD student, carried out work on the survival of salmonellae on eggs beyond FSA requirements, for which she was awarded a PhD in 2006.
Later in 2006, a PhD student, E. Kwaw, will commence a project to investigate the survival of foodborne pathogens in water with particular reference to prior exposure to suboptimal environmental conditions. It is known that the prior history of microorganisms can exert a significant influence on the subsequent lag phase when inoculated into conditions conducive to growth, although the actual growth rate is unaffected. Prior conditions may also be an important modulator of survival or death in conditions not conducive to growth. Further in this project , research at molecular level is planned to determine the effects of survival environment on metabolism and activity of microorganisms.
Theme 3: Probiotics and intestinal microbiology
In 2000, Dr A. Varnam and Dr J. Sutherland gained a Food Standards Agency research grant (£137,000 for 3 years) to develop methods to isolate and identify probiotic microorganisms in fermented milk products, in order to substantiate or refute claims of probiotic organisms on labels of such products (the "FermPro" project). Dr C. Scotti, an experienced molecular biologist, was employed as a Post-Doctoral Research Fellow in this project. Additional funding from the FSA was obtained to extend the project to include dried probiotic preparations. The outcome of the research indicated that, while the claims of major suppliers of probiotic fermented milks and dried products were justified, many claims made by smaller suppliers were not justified. The technique for isolation and identification of probiotic organisms developed by Dr Scotti and Dr Varnam is now widely considered to be the "gold standard" and has resulted in substantial knowledge and experience and a wide range of external contacts. This has led to contract work, with consequent generation of "third stream" income. It also attracts visiting workers from overseas (J. Barooi, from Iran) to the University for instruction in techniques for isolation and identification of probiotic organisms.
The work is being extended through a PhD student, E. Sarraf Zadeh, notably investigation of interactions between probiotic microorganisms and foodborne pathogens. The preliminary results will be validated using an in vitro representation of the human intestinal system. This work also has links with Theme 1, since the possibility of modelling such interactions for predictive purposes will be investigated.
Dr A Varnam was awarded a Food Standards Agency grant in 2002 (£11,500 for 6 months) to review the use of Bacillus spp. as a probiotic in animal feeds. This was a literature review and did not require laboratory work. The major conclusions of this review were XXXXXXXXXXXXXXX
Theme 4: Traditional fermentations
Traditional fermentations such as those encountered in the African sub-continent are of increasing interest in microbiology. For example, fermentation of cassava root removes naturally-occurring toxins in the plant and renders it edible. The derived product can then be made into a porridge or dried and ground into flour. If appropriately supplemented, these can provide a valuable source of protein in the African diet and it can be made suitable for specific needs such as an infant weaning food. Molecular biology is proving to be an invaluable tool to characterise and identify the microorganisms associated with fermentations. A PhD project, carried out part-time in the MRU by B. Awamaria, addresses development of an infant weaning food by nutritional supplementation of traditionally-fermented cassava.
Some microorganisms associated with traditional fermentations appear to have probiotic properties, which strongly link this theme to Theme 3. Examples include bikalga, a traditional fermentation of the seeds of Hibiscus sabdariffa. This is an alkaline fermentation carried out by strains of Bacillus spp. In 2004, the MRU was awarded a Royal Society Fellowship to enable Dr I. Ouoba to spend 3 months in the MRU identifying Bacillus spp associated with bikalga. Bikalga made with some strains of B. subtilis may have a protective effect against foodborne pathogens and therefore could have a role in prevention or reducing the duration of diarrhoeal diseases prevalent in Africa, particularly among infants and children. It is considered a safe food and there was no evidence that any of the isolates were potentially pathogenic.
Dr Ouoba joined the MRU in April 2006 as a Post-Doctoral Research Fellow, funded by the University and is continuing research into bikalga.
Other traditional fermentations studied by the MRU include evaluation of the role of lactic acid bacteria in flavour development in traditionally-produced cheeses. H. Goudjil, a Visiting Worker in the MRU has been researching the role of these organisms in North African cheeses traditionally produced from ewes' and goats' milk cheeses by nomads of the Sahara Desert.
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