Research activities of the Microbiology Group (revised April 2007 - pls note that this page is not being up-dated; refer to http://www.aqua.dtu.dk/English/Fish_products/Microbiology_group/Research.aspx)

Research activities are divided in three areas

Area: FOOD SAFETY AND PATHOGENIC MICROORGANISMS

The purpose of this project is to control Listeria monocytogenes  in fish processing and fish products. It focuses of aspects of relevance for both GHP- and HACCP-programmes. Processes such as washing, salting, cold-smoking and freezing will be evaluated with respect to listeria-reducing power. Specifically, these measures will be aimed at persistent sub-types.

Project: Microbial opportunistic pathogens

Project financed by Forskningsstyrelsen (2004-2008). Collaboration with DTU, KVL, Risø, DFVF, Rigshospitalet, SSI and others. From DIFRES: Anne Jensen, Caroline Trebbien Gottlieb, Birte F. Vogel and Lone Gram.

The purpose of this project is to determine why and how particular sub-types of Listeria monocytogenes persists in food processing and to what extend these strains are more or less virulent that other sub-types. We will determine differences in growth and adhesion of persistent versus non persistent sub-types. Also, the project will elucidate how different L. monocytogenes strains interact with epithelial defense and to what extend this interaction reflects their origin and  pathogenicity. The project will use classical bacterial methods, microscopic techniques, animal models and proteomics to determine how Listeria responds. Anne Jensen and Caroline Gottlieb are enrolled as Ph.D. students

Project: Antifouling fish

Project financed by "food for the future" programme (2005-2008). Collaboration with BioCentrum, DTU, RISØ and iNANO at Aarhus University. From DIFRES: Nete Bernbom, Jette Melchiorsen, Yoke Yin Ng and Lone Gram

The purpose of the project is to elucidate the anti-fouling mechanisms of a water based fish extract. The project will use a combination of classical bacterial methods, chemical characterization of surface layers and DNA microarrays to determine the repelling principle. Nete Bernbom is employed as post.doc.

Project: Cleaning and disinfection - PathogenCombat

Project financed by PathogenCombat (2006-2009). Collaboration with BioCentrum, DTU, and several international partners. From DIFRES: Vicky Kastbjerg and Lone Gram

The purpose of improve hygiene in the food industry by understanding how adhesion of pathogens to surfaces is facilitated by surface soiling and how this subsequently affects the removal of bacteria.  The project will use a combination of classical bacterial methods, chemical characterization of surface layers, microcopy, real-time PCR and conductometric measurements. Vikcy Kastbjerg will enroll as Ph.D. student.

Area: SEAFOOD AND PREDICTIVE MICROBIOLOGY

The flesh of live and healthy fishes is sterile, but microorganisms start growing after death/slaughter, and when only lightly preserved, spoilage of fish products is most often due to microbial activity. Any set of preserving parameters will select only a few bacterial species amongst the heterogeneous population originally present on the fish. Typically, only one or two species will be responsible for the production of metabolites associated with the off-flavours of spoilage. These are called the specific spoilage organisms and their number is inversely proportional with the storage life of the product. Studies of specific spoilage organisms in seafood are most important and knowledge about growth and metabolism of the spoilage organisms can be used to (i) determine shelf-life by establishing microbiological and chemical indices of spoilage (ii) prediction of shelf-life by development of microbial spoilage models and (iii) extension of shelf-life by targeted inhibition of the specific spoilage organisms.

Project: Optimization and application of MAP to improve quality and chilled storage in the seafood sector (MAP-KVALITET)

Project financed by the Danish Innovation program (2006-2008). Collaboration between DIFRES and Royal Greenland Seafood Ltd. Project participants from DIFRES are Nadereh Samieian, Tina Dahl Devitt, Marco Frederiksen and Paw Dalgaard (project manager). 

The project studies fresh fish in modified atmosphere packaging (MAP). Inhibition and inactivation of the specific spoilage organiusm Photobacterium phosphoreum is evaluated in studies with saithe. Mathematical models for growth of Photobacterium phosphoreum is used to evaluate chill chain distribution.  

Project: Biogenic amines in seafoods (BIOCOM)

Ph.D. project financed by the EU-SEAFOODplus program (2004-2007). Collaboration between DIFRES and the Danish Veterinary and Food Administration. Project participants from DIFRES are Jette Emborg, Tina Dahl Devitt and Paw Dalgaard (project manager). 

The project concerns the formation of toxic concentrations of histamine and other biogenic amines in chilled seafoods. The project focuses on exposure assessments and the importance of psychrotolerant bacteria Morganella psychrotolerans and Photobacterium phosphoreum.  

Project: Lightly preserved seafood in modified atmosphere packaging (MAP-LET)

Project financed by the Danish Innovation program (2004-2007). Collaboration between DIFRES and Royal Greenland Seafood Ltd. Project participants from DIFRES are Ole Mejlholm, Tina Dahl Devitt, and Paw Dalgaard (project manager). 

The project concerns preservation techniques that limit the growth of Listeria monocytogenes and spoilage microorganisms in lightly preserved seafoods in modified atmosphere packaging (MAP). A specific objective of the project is to develop mathematical models to predict the effect of organic acids and smoke components in chilled MAP products.      

Project: The impact of pancreas disease (PD) on flesh quality of Atlantic salmon. Determine underlying causes and identify strategies accelerating muscle regeneration post-infection (PD-Salmon)

Project financed by the Research Council of Norway (2007-2009). Collaboration between AKVAFORSK (Turid Mørkøre, Målfrid Bjerke), NORCONSERV (Sveinung Birkeland, Morten Sivertsvik), Veterinærinstituttet (Torunn Taksdal, Marit Wasmuth) and MATFORSK (Kirsten Hannesson) from Norway and DIFRES (Paw Dalgaard, Tina Devitt) from Denmark.  

The project concerns the effect of pancreas disease on quality attributes of Atlantic salmon post infection. The project focus on quality attributes of cold-smoked salmon where the effect of the disease on colour, texture, microbial growth and shelf-life will be specifically studied.

Area: NATURAL ANTI-BACTERIAL SYSTEMS / BACTERIAL INTERACTIONS

In a number of fish products, particularly lightly preserved fish products, bacteriological problems (e.g. L. monocytogenes) cannot be solved as the bacteria in question will be present and will be able to grow under the preservation conditions used. Therefore, alternative, consumer-friendly preservation techniques must be developed. Strategies used for other foods have included the use of protective cultures, typically lactic acid bacteria, or use of naturally occurring antibacterial compounds like enzymes. Projects within this area also investigates the use of enzymes and peptides as alternatives for cleaning and disinfection in the food industry.

Project: Roseobacter-bacteria. Stars of the oceans.

Project: Bacterial interactions in Gram-negative fish pathogenic and probiotic bacteria.

The purpose of the project is to evaluate the interaction between probiotic and pathogenic bacteria as well as beween cells in the pathogenic population. The aim is to use this understanding to develop non-antibiotic based disease control measures. We will focus on the multicellular behaviour of both potential probionts (Roseobacter) and of the pathogenic bacteria. This includes a determination of the presence and role of acylated homoserine lactones in fish pathogenic bacteria. Jesper B. Bruhn and Christiane Buchholtz are enrolled as Ph.D. students.

Project: Quorum sensing inhibtiors in food and fish quality.

Post. doctoral project funded by the Research Council for Technical Sciences. Collaboration with the Technical University of Denmark (BioCentrum and Chemical Institute). From DIFRES: Maria Rasch, Jacob D. Jensen, Lone Gram

The purpose of the project is to evaluate the potential use of compounds specifically blocking bacterial communication based on acylated homoserine lactones in food spoilage bacteria and in fish pathogenic bacteria.