Ph.D. project: Extraction, purification and evaluation of proteins from macroalgae

Department: Department of Food Science, AU

Supervisor: Trine Kastrup Dalsgaard, Associate professor, AU-FOOD

Co-supervisors: Annette Bruhn, Senior researcher, AU-BIOS and Søren Krogh Jensen, Senior research-er, AU-ANIS

Project term: May 1st 2018 – April 30th 2021

Master’s degree: MSc. in Molecular Nutrition and Food Technology, AU

Project background

Due to the increasing human population, there is a strong and growing need for proteins for feed and food, which we can culture with low impact on climate - and macroalgae (seaweed), may be a future alternative source of protein to fulfill this need. Macroalgae are grown in seawater, why they are not in competition with general land crops for neither arable land nor fresh water, which is a strong benefit looking at a greater sustainable view. Moreover, macroalgae can be cultivated without use of added nutrition and pesticides, and have shown to improve the water quality where they are grown, and can function as a CO2 sink, due to the high efficiency photosynthesis and their rapid growth, thus affecting the environment positively.
The chemical composition of the macroalgae varies from species to species and between seasons, but is also a result of developmental stage, geographic location, habitat and other environmental factors. Macroalgae contain high quality proteins, due to a high proportion of essential amino acids, which compares to more tra-ditional protein sources such as soybean meal and fishmeal, but the quantity is rather low, why protein from macroalgae need to be concentrated in order to be a potential protein source.

Aim

The aim of the project is to optimize extraction and precipitation techniques of protein from macroalgae na-tive to Danish waters, and further to do a chemical protein characterization and nutritional value evaluation hereof. Initially, the project will primarily focus on the green macroalgae Ulva lactuca (sea lettuce), due to higher protein content, but other species will be investigated as well.

Research outline

The project will focus on wet biomass extraction of protein from macroalgae, looking into the effect of different antioxidants during extraction and further into acid precipitation, testing different acids.
Moreover, seasonal variation of protein content and types of proteins (soluble vs. storage proteins), amino acid composition, as well as process-induced modifications of the extracted proteins will be tested. An overall protein chemical characterization will be performed while the protein quality will be measured by digestibility and N-balance experiments with rats using PDCAAS. As part of investigating the nutritional value, anti-nutritional factors (ANF), such as polyphenolic compounds, will be quantified.

Partners of collaboration

Center for Circular Bioeconomy (CBIO)