A Comparison of ß-Carotene, Phytoene and Amino Acids Production in Dunaliella salina DF 15 (CCAP 19/41) and Dunaliella salina CCAP 19/30 Using Different Light Wavelengths.

Strains of Dunaliella salina microalgae are of considerable research and industrial interest because they hyper-accumulate ß-carotene as well as produce high-quality protein. To explore the co-production of valuable compounds in D. salina, this study compared the production of ß-carotene, phytoene and amino acids in two strains cultivated under white, red or blue light until no further nitrogen was available. D. salina DF15 (CCAP 19/41 (PLY DF15)) produced more than 12% ß-carotene (ash-free dry weight (AFDW) basis), and red light triggered the production of 9-cis ß-carotene at a 9-cis/all-trans ß-carotene ratio of 1.5. Phytoene production was also evident in D. salina DF15 under all conditions, particularly under blue light. However, the profile of essential amino acids (EAAs) and calculation of the essential amino acid index (EAAI) was less than ideal in terms of protein quality, for both strains. Umami compounds, quantified as monosodium glutamate (MSG) equivalents, indicated a higher equivalent umami concentration (EUC) in D. salina DF15 under red light (3.2 g MSG/100 g AFDW) than in D. salina CCAP19/30. Overall, D. salina DF15 demonstrates valuable traits for further exploration and product optimisation.

Effect of Light Intensity and Wavelength on Biomass Growth and Protein and Amino Acid Composition of Dunaliella salina.

Dunaliella salina is a halotolerant, photoautotrophic marine microalga and one of the richest sources of natural carotenoids but also shows potential as a novel food source with high protein quality. This study sought to optimise the production of biomass, protein and amino acids from D. salina, alongside carotenoids using a two-stage cultivation approach based on the use of light of different intensities and quality, i.e., white, red and blue LED light. In stage 1, four white LED light intensities were tested. In stage 2, the same four light intensities from either blue or red LEDs were applied once exponential growth ceased and cells reached the stationary phase under white LED light in stage 1. Remarkably, both biomass concentration and biomass productivity showed a 1.3-1.7-fold increase in stage 2, without medium replenishment, while protein concentration and protein productivity showed an ~1.1-fold increase. The amino acid content and amino acid index remained unchanged from stage 1 to stage 2, and minimum difference was found across different light intensities. Overall, D. salina delivered so-called high protein quality, with an essential amino acid index (EAAI) of 0.99, and red light, which has previously been shown to increase carotenoid production, boosted further biomass production over and above white light, at all light intensities tested.

Dunaliella Microalgae for Nutritional Protein: An Undervalued Asset.

ß-carotene production using Dunaliella microalgae is established, yet their potential as a source of protein for food and feed applications appears to be overlooked. The rich protein content and nutritional tunability of Dunaliella make these algae intriguing sources of sustainable protein. Thus, it is of societal interest to exploit these promising proteinaceous Dunaliella traits.

Purple non-sulphur bacteria and plant production: benefits for fertilization, stress resistance and the environment.

Purple non-sulphur bacteria (PNSB) are phototrophic microorganisms, which increasingly gain attention in plant production due to their ability to produce and accumulate high-value compounds that are beneficial for plant growth. Remarkable features of PNSB include the accumulation of polyphosphate, the production of pigments and vitamins and the production of plant growth-promoting substances (PGPSs). Scattered case studies on the application of PNSB for plant cultivation have been reported for decades, yet a comprehensive overview is lacking. This review highlights the potential of using PNSB in plant production, with emphasis on three key performance indicators (KPIs): fertilization, resistance to stress (biotic and abiotic) and environmental benefits. PNSB have the potential to enhance plant growth performance, increase the yield and quality of edible plant biomass, boost the resistance to environmental stresses, bioremediate heavy metals and mitigate greenhouse gas emissions. Here, the mechanisms responsible for these attributes are discussed. A distinction is made between the use of living and dead PNSB cells, where critical interpretation of existing literature revealed the better performance of living cells. Finally, this review presents research gaps that remain yet to be elucidated and proposes a roadmap for future research and implementation paving the way for a more sustainable crop production.

Enhancement of co-production of nutritional protein and carotenoids in Dunaliella salina using a two-phase cultivation assisted by nitrogen level and light intensity.

Microalga Dunaliella salina is known for its carotenogenesis. At the same time, it can also produce high-quality protein. The optimal conditions for D. salina to co-produce intracellular pools of both compounds, however, are yet unknown. This study investigated a two-phase cultivation strategy to optimize combined high-quality protein and carotenoid production of D. salina. In phase-one, a gradient of nitrogen concentrations was tested. In phase-two, effects of nitrogen pulse and high illumination were tested. Results reveal optimized protein quantity, quality (expressed as essential amino acid index EAAI) and carotenoids content in a two-phase cultivation, where short nitrogen starvation in phase-one was followed by high illumination during phase-two. Adopting this strategy, productivities of protein, EAA and carotenoids reached 22, 7 and 3 mg/L/d, respectively, with an EAAI of 1.1. The quality of this biomass surpasses FAO/WHO standard for human nutrition, and the observed level of ß-carotene presents high antioxidant pro-vitamin A activity.

Light regime and growth phase affect the microalgal production of protein quantity and quality with Dunaliella salina.

The microalga Dunaliella salina has been widely studied for carotenogenesis, yet its protein production for human nutrition has rarely been reported. This study unveils the effects of growth phase and light regime on protein and essential amino acid (EAA) levels in D. salina. Cultivation under 24-h continuous light was compared to 12-h/12-h light/dark cycle. The essential amino acid index (EAAI) of D. salina showed accumulating trends up to 1.53 in the stationary phase, surpassing FAO/WHO standard for human nutrition. Light/dark conditions inferred a higher light-usage efficiency, yielding 5-97% higher protein and 18-28% higher EAA mass on light energy throughout the growth, accompanied by 138% faster growth during the light phase of the light/dark cycle, compared to continuous light. The findings revealed D. salina to be especially suitable for high-quality protein production, particularly grown under light/dark conditions, with nitrogen limitation as possible trigger, and harvested in the stationary phase.

High variability in nutritional value and safety of commercially available Chlorella and Spirulina biomass indicates the need for smart production strategies.

Microalgal biomass production is a resource-efficient answer to the exponentially increasing demand for protein, yet variability in biomass quality is largely unexplored. Nutritional value and safety were determined for Chlorella and Spirulina biomass from different producers, production batches and the same production batch. Chlorella presented a similar protein content (47 ±â€¯8%) compared to Spirulina (48 ±â€¯4%). However, protein quality, expressed as essential amino acid index, and digestibility were lower for Chlorella (1.1 ±â€¯0.1 and 51 ±â€¯9%, respectively) compared to Spirulina (1.3 ±â€¯0.1 and 61 ±â€¯4%, respectively). Generally, variability was lower between batches and within a batch. Heavy metals, pesticides, mycotoxins, antibiotics and nitrate did not violate regulatory limits, while polycyclic aromatic hydrocarbon levels exceeded the norm for some samples, indicating the need for continuous monitoring. This first systematic screening of commercial microalgal biomass revealed a high nutritional variability, necessitating further optimization of cultivation and post-processing conditions. Based on price and quality, Spirulina was preferred above Chlorella.

Closing Domestic Nutrient Cycles Using Microalgae.

This study demonstrates that microalgae can effectively recover all P and N from anaerobically treated black water (toilet wastewater). Thus, enabling the removal of nutrients from the black water and the generation of a valuable algae product in one step. Screening experiments with green microalgae and cyanobacteria showed that all tested green microalgae species successfully grew on anaerobically treated black water. In a subsequent controlled experiment in flat-panel photobioreactors, Chlorella sorokiniana was able to remove 100% of the phosphorus and nitrogen from the medium. Phosphorus was depleted within 4 days while nitrogen took 12 days to reach depletion. The phosphorus and nitrogen removal rates during the initial linear growth phase were 17 and 122 mg·L(-1)·d(-1), respectively. After this initial phase, the phosphorus was depleted. The nitrogen removal rate continued to decrease in the second phase, resulting in an overall removal rate of 80 mg·L(-1)·d(-1). The biomass concentration at the end of the experiment was 11.5 g·L(-1), with a P content of approximately 1% and a N content of 7.6%. This high algal biomass concentration, together with a relatively short P recovery time, is a promising finding for future post-treatment of black water while gaining valuable algal biomass for further application.