Simona Lucakova

Finding an optimal artificial light source for photoautotrophic microalgae cultivation is a complex task. This study provides missing data for Limnospira (Arthrospira) maxima cultivation and key aspects for evaluating this issue. Rigorous experimental datasets were analyzed to clarify the relationship between illumination (LEDs) characteristics (intensity and spectral composition) and biomass/pigments production, considering energy costs in the technologically relevant light-limited region of the photosynthesis-irradiance curve (up to 550 µmol/m²/s). Using the same light spectra (cool white), higher light intensities consistently increased biomass productivity, with a maximum of 0.97 g/L/day at 550 µmol/m²/s. However, the lowest energy costs per unit of biomass and pigments were achieved under low light intensity of 100 µmol/m²/s (0.57 kWh/g of biomass, 2.45 kWh/g of phycocyanin, 51.4 kWh/g of carotenoids, and 15.4 kWh/g of chlorophyll a). When spectral composition was varied at constant light intensity of 50 µmol/m²/s, the highest productivity and lowest energy costs were observed under daylight white and warm white light, followed by red. Surprisingly, pigment content remained relatively stable across all spectra. These findings provide practical guidance for optimizing L. maxima cultivation by balancing productivity and energy efficiency.

In vitro ACE-1 inhibitory peptides were characterised previously from a number of microalgal species including Spirulina platensis (peptide IAPG), Chlorella vulgaris (peptides FDL, AFL, VVPPA), Isochrysis galbana (peptide YMGLDLK), Chlorella sorokiniana (peptides IW and LW) and indeed Nannochloropsis oculata (peptides GMNNLTP and LEQ). The isolation of protein from Nannochloropsis oculata using a combination of ammonium salt precipitation and xylanase treatment of resulting biomass combined with molecular weight cut off filtration to produce a permeate and characterisation of bioactive peptides is described. The Angiotensin-1-converting enzyme (ACE-1) IC₅₀ value for the generated permeate fraction was 370 µg/mL. Ninety-five peptide sequences within the permeate fraction were determined using mass spectrometry and eight peptides were selected for chemical synthesis based on in silico analysis. Synthesized peptides were novel based on a search of the literature and relevant databases. In silico, simulated gastrointestinal digestion identified further peptides with bioactivities including ACE-1 inhibitory peptides and peptides with antithrombotic and calcium/calmodulin-dependent kinase II (CAMKII) inhibition. This work highlights the potential of Nannochloropsis oculata biomass as both a protein and bioactive peptide resource, which could be harnessed for use in the development of functional foods and feeds.

Microalgae are a known source of proteins, prebiotics, lipids, small molecules, anti-oxidants and bioactives with health benefits that can be harnessed for the development of functional foods, feeds, cosmeceuticals and pharmaceuticals. This review collates information on the supply, processing costs, target markets and value of microalgae, as well as microalgal proteins, lipids, vitamins and minerals. It discusses the potential impact that microalgae could have on global food and feed supply and highlights gaps that exist with regards to the use of microalgal proteins and ingredients as foods and supplements.

Mercury is a ubiquitous environmental pollutant of dominantly anthropogenic origin. A critical concern for human health is the introduction of mercury to the food chain; therefore, monitoring of mercury levels in agricultural soil is essential. Unfortunately, the total mercury content is not sufficiently informative as mercury can be present in different forms with variable bioavailability. Since 1990, the use of bioreporters has been investigated for assessment of the bioavailability of pollutants; however, real contaminated soils have rarely been used in these studies. In this work, a bioassay with whole-cell bacterial bioreporter Escherichia coli ARL1 was used for estimation of bioavailable concentration of mercury in 11 soil samples. The bioreporter emits bioluminescence in the presence of Hg(II). Four different pretreatments of soil samples prior to the bioassay were tested. Among them, laccase mediated extraction was found to be the most suitable over water extraction, alkaline extraction, and direct use of water-soil suspensions. Nevertheless, effect of the matrix on bioreporter signal was found to be severe and not possible to be completely eliminated by the method of standard addition. In order to elucidate the matrix role, influences of humic acid and selected metal ions present in soil on the bioreporter signal were tested separately in laboratory solutions. Humic acids were found to have a positive effect on the bioreporter growth, but a negative effect on the measured bioluminescence, likely due to shading and Hg binding resulting in decreased bioavailability. Each of the tested metal ions solutions affected the bioluminescence signal differently; cobalt (II) positively, iron (III) negatively, and the effects of iron (II) and nickel (II) were dependent on their concentrations. In conclusion, the information on bioavailable mercury estimated by bioreporter E. coli ARL1 is valuable, but the results must be interpreted with caution. The route to functional bioavailability bioassay remains long.