Doctoral Defense in Food Science – Monica Daugbjerg Christensen

On Thursday, October 2, 2025, Monica Daugbjerg Christensen will defend her doctoral thesis in Food Science at the Faculty of Food Science and Nutrition, University of Iceland.

The thesis is entitled:
Refining marine polysaccharides and their immunomodulatory effects
(Einangrun og niðurbrot sjávarfjölsykra og mat á ónæmismótandi áhrifum þeirra)

Opponents:
Dr. Kari Tvete Inngjerdingen, Associate Professor, University of Oslo
Dr. Finn Aachmann, Professor, Norwegian University of Science and Technology

Supervisors:
Hildur Inga Sveinsdóttir, Assistant Professor
Guðjón Þorkelsson, Professor

Advisors:
Guðmundur Óli Hreggviðsson, Professor and Senior Specialist
Jóna Freysdóttir, Professor

Doctoral committee members:
Ólafur H. Friðjónsson, Division Leader; and Eva Nordberg Karlsson, Professor.

The defense will be chaired by Professor Ingibjörg Gunnarsdóttir, Vice Dean of the Faculty of Food Science and Nutrition. The ceremony will take place in the Ceremonial Hall (Hátíðasalur) of the University of Iceland and will begin at 13:30.

Abstract

Brown seaweed is a rich source of structurally diverse polysaccharides with promising bioactive properties. This study investigated in four ways how enzymatic refining can modify marine polysaccharides and influence their immunomodulatory effects. 1) A novel sulfatase, SulA1, cloned from a marine Arthrobacter strain, was characterized, and shown to selectively act on the chondroitin sulfate monosaccharide N-Acetyl-D-galactosamine-4-sulfate. This introduced the possibilities for the use of SulA1 in targeted desulfation strategies to alter bioactivity of targeted molecules. 2) Laminarin from three brown seaweed species (Laminaria digitata, L. hyperborea, and Saccharina latissima) was extracted and enzymatically modified. The laminarin derivatives were structurally analysed and found to distinctly regulate dendritic cell activity depending on their molecular size and branching pattern. These data suggest that different laminarin derivatives may have different therapeutic applications within the immune system. 3) Fucoidan from S. latissima was enzymatically refined into defined molecular weight fractions. The low molecular weight fucoidan fraction significantly suppressed the secretion of the pro-inflammatory cytokine by dendritic cells, indicating potential therapeutic applications against inflammatory diseases. 4) Two enzymatically generated alginate oligosaccharide fractions, enhanced cytokines secretion by dendritic cells and promoted Th1 responses in co-cultures with T cells. These findings highlight distinct immunomodulatory properties of alginate oligosaccharides with potential therapeutic relevance in inducing inflammatory responses, e.g. as adjuvants or in cancer treatment. Collectively, these results demonstrate that targeted enzymatic modifications can reshape the immunomodulatory activity of marine-derived polysaccharides, positioning them as promising candidates for therapeutic development. At the same time, this strategy enhances the efficient use of seaweed biomass and supports the creation of sustainable, high-value products with potential applications in pharmaceuticals and nutraceuticals.

About the doctoral candidate

Monica Daugbjerg Christensen was born in 1988 in Denmark. She graduated from the Mathematics track at Allerød Gymnasium in 2007. She completed a B.Sc. in Biology and Biotechnology at the University of Copenhagen in 2011, followed by an M.Sc. in Biology and Biotechnology from the same university in 2014.

In 2017, she began her doctoral studies at the Faculty of Food Science and Nutrition, University of Iceland. Her research was carried out at the Biotechnology Department of Matís ohf. and the Department of Immunology, Landspítali – The National University Hospital of Iceland. During her studies, she also participated in teaching and student supervision at the Department of Immunology.

Her parents are Jens Hesselbjerg Christensen and Conni Daugbjerg Christensen. Monica is married to Henrik Holst Jensen, and together they have two sons: Patrik Nói (5 years old) and Jakob Máni (1 year old).