Kim Jye Lee Chang

Aurantiochytrium not only excels in producing long-chain polyunsaturated fatty acids such as docosahexaenoic acid for humans, but it is also a source of essential fatty acids with minimal impacts on wild fisheries and is vital in the transfer of atmospheric carbon to oceanic carbon sinks and cycles. This study aims to unveil the systems biology of lipid production in the Australian Aurantiochytrium sp. TC20 by comparing the transcriptomic profiles under optimal growth conditions with increased fatty acid production from the early (Day 1) to late exponential growth phase (Day 3). Particular attention was paid to 227 manually annotated genes involved in lipid metabolism, such as FAS (fatty acid synthetase) and subunits of polyunsaturated fatty acids (PUFA) synthase. PCA analysis showed that differentially expressed genes, related to lipid metabolism, efficiently discriminated Day 3 samples from Day 1, highlighting the key robustness of the developed lipid-biosynthesis signature. Highly significant (pFDR < 0.01) upregulation of polyunsaturated fatty acid synthase subunit B (PFAB) involved in fatty acid synthesis, lipid droplet protein (TLDP) involved in TAG-synthesis, and phosphoglycerate mutase (PGAM-2) involved in glycolysis and gluconeogenesis were observed. KEGG enrichment analysis highlighted significant enrichment of the biosynthesis of unsaturated fatty acids (pFDR < 0.01) and carbon metabolism pathways (pFDR < 0.01). This study provides a comprehensive overview of the transcriptional landscape of Australian Aurantiochytrium sp. TC20 in the process of fatty acid production.

The sustainable production of marine ingredients is increasingly important, valued by manufacturers, government, and authorities, as well as by environmentally aware consumers

The spatiotemporal distribution of phytoplankton in estuaries is indicative of processes and transport across the land–ocean aquatic continuum (LOAC). Estuaries, as biogeochemically and physically active systems, process large amounts of nutrients and organic matter influencing the transformation of ecological functions. The transformation of the water column drives variation in phytoplankton composition, biomass, and their spatial distribution. Understanding the dynamics of nutrients and organic matter is challenging, yet it provides a comprehensive insight into phytoplankton spatiotemporal distribution across estuaries. Multiple studies have been conducted to understand the spatiotemporal distribution of phytoplankton. Recently, phytoplankton photosynthetic pigments, fatty acids and stable isotopes have been widely used to identify and quantify phytoplankton distribution. This review highlights the use of biogeochemical markers to identify phytoplankton functional groups. It also assesses the current understanding of patterns in the spatiotemporal distribution of phytoplankton and the impact of physical and environmental factors on their distribution in estuaries and coastal oceans. The review will also gather information from in situ sampling studies to evaluate the current state of knowledge and identify gaps.

Algae-derived protein has immense potential to provide high-quality protein foods for the expanding human population. To meet its potential, a broad range of scientific tools are required to identify optimal algal strains from the hundreds of thousands available and identify ideal growing conditions for strains that produce high-quality protein with functional benefits. A research pipeline that includes proteomics can provide a deeper interpretation of microalgal composition and biochemistry in the pursuit of these goals. To date, proteomic investigations have largely focused on pathways that involve lipid production in selected microalgae species. Herein, we report the current state of microalgal proteome measurement and discuss promising approaches for the development of protein-containing food products derived from algae.

Additional and alternative sustainable food resources are needed as the global human population increases. Marine fishes have long provided essential nutrients, such as omega-3 long-chain (≥C20) polyunsaturated fatty acids (n-3 LC-PUFA), protein, and vitamins to meet human dietary requirements and feed for agricultural production. Many current commercial fish stocks are depleted or fully exploited, but oceanic mesopelagic fishes, particularly the myctophids (lanternfishes), represent a potentially very large and unfished resource. This review analysed the literature on nutritional and biochemical compositions of myctophids as a first step towards understanding the health benefits and risks of consuming them. We found that myctophids have high levels of protein (11–23% wet weight, WW) and variable lipid content (0.5–26% WW). In most species, desirable triacylglycerols or phospholipids dominated over less-desirable wax esters, and most have abundant amounts of health-promoting n-3 LC-PUFA, such as DHA and EPA. Myctophids have low levels of heavy metals and persistent organic pollutants. Most nutritional information is available for species from the Pacific and Southern Oceans and for the genera Benthosema, Electrona, and Diaphus. Myctophids generally possess favourable nutritional profiles, but major gaps in knowledge regarding their stock assessment, ecology and the economic viability for their harvest are barriers to developing sustainable fisheries.

Heterosigma akashiwo is the only raphidophyte described for Chilean waters. A recent 2021 fish-killing bloom event of this raphidophyte ignited scientific research, but the ichthyotoxic mechanism and environmental conditions that promote its growth are still unclear. This is the first study confirming the occurrence of H. akashiwo in Chilean waters on the basis of the region D1/D2 of the 28S ribosomal gene. The pigment signature of the CREAN_HA03 strain revealed chlorophyll-a, fucoxanthin, and violaxanthin as the most abundant pigments, but profiles were variable depending on culture and field conditions. A factorial temperature–salinity growth experiment showed a maximal growth rate of 0.48 d⁻¹ at 17 °C and 35 in salinity, but reached a maximal cell abundance of ~50,000 cells mL⁻¹ at 12 °C and 25 in salinity. The fatty acid profile included high levels of saturated (16:0) and polyunsaturated (18:4 ω3; 20:5 ω3) fatty acids, but superoxide production in this strain was low (~0.3 pmol O^2– cell⁻¹ h⁻¹). The RTgill-W1 bioassay showed that the H. akashiwo strain was cytotoxic only at high cell concentrations (>47,000 cells mL⁻¹) and after cell rupture. In conclusion, salmon mortality during H. akashiwo bloom events in Patagonian fjords is likely explained by the high production of long-chain PUFAs at high cell densities, but only in the presence of high ROS production.

The importance of microalgal lipids for the survival and growth of shrimp postlarvae has been recognized in a range of studies. Microalgae with fast growth rates and high levels of polyunsaturated fatty acids (PUFA) are considered vital to maximise production and minimise cost in shrimp larviculture. The lipid content and fatty acid composition of microalgae used in shrimp production varies substantially between the algal classes and species being used in Vietnam. This study aims to characterise microalgal lipid and fatty acid (FA) profiles and evaluate the most promising species under growth conditions that are most suitable for shrimp aquaculture. Here, we report that the highest lipid contents were obtained in the Haptophyta microalgae, Tisochrysis lutea and Isochrysis galbana, at 90.3 and 61.1 mg/g, respectively. In contrast, two of the most popular diatom species being used for shrimp larval cultivation in Vietnam, Thalassiosira pseudonana and T. weissflogii, displayed the lowest lipid contents at 16.1 mg/g. Other microalgal species examined showed lipid contents ranging from 28.6 to 55 mg/g. Eicosapentaenoic acid (EPA, 20:5ω3) ranged from 0.6 to 29.9% across the species, with docosahexaenoic acid (DHA, 22:6ω3) present at 0.01 to 11.1%; the two omega (ω)–3 long-chain (LC, ≥C20) LC-PUFA varied between the microalgae groups. Polar lipids were the main lipid class, ranging from 87.2 to 97.3% of total lipids, and triacylglycerol was detected in the range of 0.01 to 2.5%. Saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) increased and PUFA decreased with increasing growth temperatures. This study demonstrated the differences in the lipid contents and FA profiles across 10 microalgal species and the effect of the higher temperature growing conditions encountered in Vietnam.

The Labyrinthulomycetes or Labyrinthulea are a class of protists that produce a network of filaments that enable the cells to glide along and absorb nutrients. One of the main two Labyrinthulea groups is the thraustochytrids, which are becoming an increasingly recognised and commercially used alternate source of long-chain (LC, ≥C₂₀) omega-3 containing oils. This study demonstrates, to our knowledge for the first time, the regiospecificity of the triacylglycerol (TAG) fraction derived from Australian thraustochytrid Aurantiochytrium sp. strain TC 20 obtained using ¹³C nuclear magnetic resonance spectroscopy (¹³C NMR) analysis. The DHA present in the TC 20 TAG fraction was determined to be concentrated in the sn-2 position, with TAG (16:0/22:6/16:0) identified as the main species present. The sn-2 preference is similar to that found in salmon and tuna oil, and differs to seal oil containing largely sn-1,3 LC-PUFA. A higher concentration of sn-2 DHA occurred in the thraustochytrid TC 20 oil compared to that of tuna oil.

Food processing can generate large amounts of carbohydrate-rich waste that inevitably has environmental and social impacts. Meanwhile, certain heterotrophic marine microorganisms, including algae and thraustochytrids, have the potential to convert carbohydrate-rich substrates into oil-rich biomass over relatively short time frames. To assess the merits of this apparent synergy, an initial conceptual process was developed based on the use of raw potato processing waste as feed in an algal bioreactor to produce bio-oil for further use within the food industry. A practical flowsheet was established with a conventional 200 kL bioreactor whereby the unit processes were identified, the mass balance developed, and estimates made of the various material and energy demands. These inputs were used to develop a baseline life cycle assessment (LCA) model and to identify opportunities for reducing environmental impacts. With the functional unit (FU) being 1 tonne cooking oil, the baseline configuration had a greenhouse gas (GHG) footprint of 2.4 t CO₂-e/FU, which is comparable to conventional process routes. More detailed LCA revealed that electricity for stirring the bioreactor contributed approximately 78% of the total GHG footprint. By adjusting the operating conditions, the most promising scenario produced 0.85 t CO₂-e/FU—approximately four times less than the conventional process—and shows the potential advantages of applying LCA as a tool to develop and design a new production process.

The green alga Botryococcus braunii produces abundant hydrocarbons, in the form of drop-in biodiesel, which promoted interest in the species as a renewable fuel. However, despite the observation of dense populations in the wild, Botryococcus grows very slowly in culture, severely limiting its potential for development as a bioresource. Undertaking a biodiscovery program, we found new strains of Botryococcus in locations ranging from tropical to temperate Australia and from both fresh and brackish waters. As part of the ecophysiological characterisation of this new biodiversity, lipid and pigment compositions were studied for six new strains from six different locations. The strains were inoculated in either freshwater or brackish (salinity of 4)-based medium and maintained over 150 days. The growth of cultures was studied continuously, while lipid and pigment composition were analysed at final harvest on day 150. No significant differences in growth rate between fresh and brackish media were observed. Some strains were more tolerable of brackish conditions than others with a link between salinity tolerance and original location. The use of lower salinity (4 ppt) had a minimal effect on lipid composition, with only two of the six strains showing a different hydrocarbon profile in comparison to the other strains; pigment composition showed only minor variations for fresh and brackish water cultures, although the concentrations varied significantly with the freshwater cultures containing higher pigment concentrations.