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Title: Evaluation of toxicity and biochemical characterisation of a microalgal diatom
Authors: Beekrum, Lamees 
Keywords: Natural resources;Microalgae;Marine diatom
Issue Date: May-2023
One ofthe critical challengesthat we face in the 21st century isthe need to feed an ever-increasing
human population with increasingly limited natural resources. Microalgae have emerged as a
potentialsolution for global food security as a sustainable biological food source for humans due
to their nutrient-rich composition, particularly rich protein and bioactive compoundsthat provide
potential benefits for human health. By establishing microalgae as a new food platform, we can
increase the supply of these essential productsto address global demandsin a more efficient and
environmentally sustainable way. These under-exploited organisms have been consumed in the
human diet for thousands of years. Microalgae cultivation does not compete with land and
resources required for traditional crops and has a superior yield compared to terrestrial crops.
Diatoms are a major group of microalgae in the phytoplankton community and have the potential
to be engineered into cell factoriesforthe sustainable production of bioactive compoundsin food
and nutraceutical industries.
This study aimed to characterise a rapidly growing marine diatom in terms of its toxicity and
biochemical profile. This was done by evaluating the safety profile and biochemical
composition, characterising the soluble protein, and investigating the carbohydrate profile with
specific emphasis of β-glucan and its effect of cardioprotective properties on ferric-induced
oxidative cardiac injury in a rat model.
Based on Basic Local Alignment Search Tool (BLAST) analysis, the strain showed the closest
similarity to Amphora sp. (JF834543.1) with 99.5% and istherefore represented as Amphora sp.,
accession number MW721231. The bacterial reverse mutation assay found no evidence of
mutagenicity on the methanolic, aqueous, and hexane extracts of Amphora sp. and was found
to exert low levels of cytotoxicity against Peripheral Blood Mononuclear Cells (PBMC). A 28-
day acute oral toxicity assessment on male Wistar rats showed an absence of adverse effects
and mortality in the rats.
The biomass exhibited a low lipid profile, modest protein content, notable amino acid content,
and excellent carbohydrate and mineral content. Results of this study for antioxidant assays
displayed low to moderate activities. Protein extracted using three-phase partitioning (TPP)
treatment showed that the protein concentration and total amino acid content were substantially
higher in the protein-enriched biomass extract when compared to the dried biomass. The
solubility of the protein-enriched biomass extract increased with the increase in pH within the range of pH 2 to pH 12. The biomass consisted of a simple monosaccharide profile comprising
glucose, rhamnose, and mannose, and a β-glucan content of approximately 9%.
The cardioprotective properties ofthe β-glucan extract on ferric-induced oxidative cardiac injury
did not improve the glutathione (GSH) level significantly, it led to increased superoxide
dismutase (SOD) and catalase activities, while depleting malondialdehyde (MDA), NO (nitric
oxide), low-density lipoprotein cholesterol levels, and simultaneously elevating triglycerides
and high-density lipoprotein (LDL) cholesterol levels. GC-MS analysis revealed a complete
depletion of the lipid metabolites. Our results advocate the protective capabilities of the β-glucan
extract against ferric-induced oxidative cardiac injury as portrayed by its ability to stall oxidative
stress and modulate cardiac lipid metabolism while inhibiting the acetylcholinesterase and lipase
activities. These results display that the β-glucan extract could be utilized as an alternative for
the development of nutraceuticals for maintaining cardiac health.
The diversity of food bioactive molecules obtained from microalgae makes these microorganisms a bioresource with full potential of exploitation in the food industry. The richness of
compounds in microalgae can contribute to develop an algal-based food industry, focusing on
producing and utilizing microalgae for innovative functional food products. Overall, this study
demonstrated the potential utilization of the diatom, Amphora sp. as a potential ingredient and
nutraceutical in foods.
Submitted in fulfillment of the requirements for the degree of Doctor of Food Science and Technology: Biotechnology and Food Science, Durban University of Technology, Durban, South Africa, 2023.
Appears in Collections:Theses and dissertations (Applied Sciences)

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