Biocentrum at the Technical University of Denmark

BioCentrum (BiC) is an Institute at the Technical University of Denmark (DTU) and represents the largest concentration of biotechnological research at university level in Denmark. BiC has a long tradition of food research and teaching and has for many years been involved in different MSc programmes in Food Science and Technology. It is involved with food graduate schools in partnership with the Faculty of Life Sciences at University of Copenhagen (LIFE KU) under the name the Centre for Advanced Food Studies (LMC).

LMC coordinates the scientific activities and higher education within the food area and serves as a unique partner for the private and public food sector in Denmark. This year BiC DTU became part of a much larger organisation within the food science area, since DTU has fused with, among others, The National Food Institute and the National Veterinary Institute. A natural consequence of this has been to coordinate all old and new DTU food activities under the name FoodDTU. We anticipate that BiC DTU will continue to play a major role in some focused food research areas in the years to come.

This article will present a flavour of the food research at BiC DTU represented by four of the major groups involved in different aspects of food research.

Centre for Microbial Biotechnology (CMB)

The food research in CMB is mainly focused on various aspects of food mycology. The prediction of fungal spoilage and mycotoxin formation is one of the most important issues in food safety today. The use of fungi as starter cultures or for biotechnological production of food ingredients also depends on deep knowledge of the species and isolate used. CMB is unique in the world as it is able to combine traditional mycological methods, including in depth chemical characterisation and DNA sequence data, and have a great knowledge base and expertise in projects involving the phenotypic characterisation of fungi. CMB has a unique collection of more than 30,000 strains for accurate identification at species level using physiological and ecological criteria as well as other phenotypic characteristics such as fingerprinting of mycotoxins and other secondary metabolites. Our analytical platform consists of numerous HPLC systems coupled to diode-array detection and to high-resolution mass spectrometry. For advanced data analysis CMB uses chemometrics, image-analysis, and new in-house algorithms to search for UV and HR-MS data in in-house databases.

Mycotoxins in dairy products

During the past ten years the use of maize silage as cattle feed has increased dramatically in Denmark. Apparently this has led to some years with an unusually high death rate among high milk yielding cattle livestock. Contamination of silage in Denmark with mycotoxins from Fusarium growing on the maize in the field has been suspected to be the main cause of the observed cases. However, other fungi have been reported to be the major “secondary” contaminants during the ensiling process, while fungi other than Fusarium mycotoxins could be the source. BiC is involved in a large project with the overall aim of establishing the role of mycotoxins in this scenario. So far it has been shown that the climate has quite dramatic effect on the associated fungi (and thereby possible mycotoxin production) of the maize as one year showed Fusarium avenaceum to be the major contaminant, whereas the following year showed F. culmorum, F. equiseti and F. crockwellense to be the dominating species.

Development of DNA chip based methods are also in progress allowing fast detection of the fungi source in real samples. Finally the metabolism and toxicity of significant known and unknown metabolites are under investigation with the overall aim of establishing whether any fungal derived metabolite might be carried over from maize silage via cattle in dairy products.

Centre for Systems Microbiology

The research activities within CSM span from projects looking for new ways to prevent growth of food-borne pathogens to projects attempting to improve the functionality of starter cultures used in the dairy industry. CSM has a highly recognised knowledge base in physiology and genetics and a strong expertise in genomics, proteomics and metabolomics. Genetic engineering is used as a tool to create new varieties where enzyme activities have been perturbed in order to access the importance of the system components. Bio-mathematical tools are then used to integrate the experimental data into descriptive models and ultimately into level descriptions of selected model systems.

Detection of bacteriophage-infected cells of Lactococcus lactis using flow cytometry

Lactic acid bacteria are used extensively in the manufacture of a broad range of fermented dairy products. In many of these applications, bacteriophage infection constitutes a serious problem leading to either complete loss of the fermentation batch or an altered flavour. Many strategies to prevent phage infections have been tested, including phage-resistant bacterial strains and plans for rotational changes of phage resistant cultures. Although these strategies have had some success in preventing phage infections, they cannot completely prevent bacteriophage attack.

We discovered that before the infected bacterial cells lyse, cells with low-density cell walls appear. These cells can be detected on cytograms of light scatter versus fluorescence of stained DNA where they form a unique population, isolated from the uninfected bacteria (see Figure 1). This discovery has now led to the development of a fast and sensitive method to detect bacteria infected with bacteriophages (Michelsen and Jensen, patent pending).

The new method allows detection of well below one per cent of infected cells in a culture and is suitable for running in a continuous on-line set-up with detection every two to three minutes.

Centre for biological sequence analyses

The food research at CBS is concentrated in the Nutritional Immunology Group. The Nutritional immunology group focuses on the way food components affect the human immune system–positively or negatively. The aim is to characterise effects of dietary changes on the immune system; to identify components with positive effects; and explore their mechanisms of action.

The effect of polyunsaturated fatty acids on CD4+ T cell responses

Activation of T cells is an essential part of the cell mediated immunity. A central element in T cell activation is the stimulation of the main antigen presenting cells, the dendritic cells (DC), which subsequently activate the T cells. Although the nature of the DC stimulation is known to affect the T cells response, less is known of how dietary factors, such as dietary fatty acid composition, affects the activation of T-cells. The fatty acid composition of the cell membrane determines their functionality and can alter the efficiency in the signalling between DC and T cells. Therefore, we have addressed whether changes in the dietary n-6/n-3 PUFA ratio affect the capacity to activate a subclass of the T cells, the CD4+ T cells either by direct activation on the T cell, or through dendritic cells that have been matured with different types of gut bacteria (probiotic and non-probiotic).

Our results show that T cell activation, both through dendritic cells and direct receptor activation on the T cell surface, is highly influenced by the cellular n-6/n-3 PUFA ratio. Incorporation of n-3 PUFA into cellular lipids impairs proliferation, and the expression of several different surface molecules essential for T cell activation. However, differences in the maturation level of dendritic cells, caused by the different gut bacteria, also impact these parameters, although the influence of the n-6/n-3 PUFA ratio is more pronounced.

Collectively, the data shows that both the dietary fatty acid composition and the type of dendritic cell stimulations affect the activation potential of CD4+ T cells, but changing the dietary n-3 PUFA intake results in a greater effect than changing the bacterial dendritic cell stimulus. Thus, it is essential that PUFA intake is considered, when discussing effects of dietary components on immunity.

Enzyme and Protein Chemistry Group

The main activities within food science in EPC is related to the central know-how in relation to protein chemistry; the interaction between the structure of proteins and carbohydrates; protein engineering and protein structure/function relationship investigation; and the influence on intestinal absorption of micro food substances and nutritious effects based on advanced protein technology. The EPC also hosts a proteomic platform as well as a protein analysis unit.

The group has its strength within protein chemical and biochemical methodology, and the majority of the activities lie within the fields of raw materials and nutrition.

Recently protein chemistry in EPC has been strengthened by interdisciplinary research on quality related molecular interactions with particular emphasis on protein engineering; protein structure/function relationships; protein-carbohydrate interactions; and cereal proteome analysis. This has enabled the creation of a complementary increase in the BiC activities and the establishment of integrated molecular biological/protein chemical activities of BiC.

Proteome analysis reveals genes coding for quality properties

Food with a high whole-grain content can counteract lifestyle-related diseases like coronary heart disease and diabetes II. In the EU project HEALTHGRAIN, EPC takes part in examining what exactly makes whole-grain healthy. 43 laboratories and a large number of industries with an interest in the subject participate in the project, including an associated industry forum. Using proteome analysis, EPC is working to map protein profiles for various protein nuclei. Researchers use 2D-gel electrophoresis and mass spectrometry to identify interesting proteins. The objective is to gather knowledge and develop tools to analyse known wheat varieties and to map genes coding for properties important to refinement, processing of food such as bread, pasta, and cereals and for the positive nutrition characteristics and the associated metabolism in the body.

In the project, EPC is collaborating with other wheat protein specialists from a French state research institute and a number of analysis chemists with an expertise in cereal micro and macro nutrients from about 15 different European countries. EPC can contribute basic knowledge linking cereal growth and nutritional properties with their genetic properties enabling the development of specially improved cereals and food production processes.