Bioactivity Potential of an Arctic Marine Diatom Species Cultivated at Different Conditions

Abstract

Microalgae have proven to contain a vast amount of beneficial, high value compounds like proteins, lipids and powerful antioxidants as well as some interesting bioactive compounds. Nevertheless, microalgae are severely underrepresented in conjunction with marine bioactive natural product discovery. This thesis aims to unlock bioactivity potential of a microalgae species from the most abundant and diverse group of microalgae, namely the diatoms, by bioassay guided isolation. This diatom species is isolated from northern Arctic waters, where research on bioactivity potential in diatoms are poorly investigated. Five samples of raw biomass from a diatom species cultivated at five different conditions were extracted, fractionated through FLASH chromatography and screened in five different bioassays; an antibacterial assay against five bacteria strains (Staphylococcus aureus, Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa and Streptococcus agalactiae), an anti-biofilm assay (against S. epidermidis biofilm-formation), a MTS cell viability assay with three different cell lines (human melanoma A2058, human colon carcinoma HT29, and human pulmonary fibroblast MRC-5), a cellular antioxidant activity assay (with a THP-1 cell line) and an anti-inflammatory assay (with a HepG2 cell line). Some selected samples were fractionated further by HPLC chromatography and screened again for anti-biofilm and anti-inflammatory properties. Bioactivity was detected in all assays, and interestingly, some variation was observed within the assays for the different cultivation conditions. This indicated that the metabolite bioactivity profile of the diatom might have changed due to the varying pre-experiment cultivation conditions. The results demonstrate the huge bioactivity potential of diatoms, and that modification of cultivation conditions might be used to our advantage to obtain bioactive fractions with a different range of activities.