Search Results (28)

Microalgae are increasingly recognized as promising biostimulants for sustainable agriculture, yet their potential remains underexplored due to the complexity of biostimulant activity and the vast diversity of species. Efficient standardized screening approaches are therefore needed. In this study, a high-throughput screening platform assessed the biostimulant activity of five microalgal species (Limnospira platensis, Chlorella vulgaris, Dunaliella salina, Microchloropsis gaditana, and Isochrysis galbana) in Arabidopsis thaliana. The system enabled full life-cycle assessment of A. thaliana under optimal and drought stress conditions, incorporating three application methods (soil amendment, irrigation, foliar spray) and a wide concentration range of 0.01–0.5 g/L. Biostimulant efficacy depended strongly on concentration and application method. Irrigation-based applications generally enhanced drought tolerance but delayed bolting and flowering. The highest concentration inhibited germination and root elongation, likely due to bioactive compound toxicity rather than salinity or pH. L. platensis exhibited broad activity across environmental conditions, while I. galbana likewise showed wide-ranging effects, including enhanced generative growth. In contrast, D. salina and M. gaditana primarily improved drought tolerance, and C. vulgaris acted mainly under optimal conditions. These findings highlight the value of A. thaliana to accommodate rapid biostimulant screening and identify both novel and established microalgae for further validation in crops. Full article

There is an increasing industrial demand for sustainable resources for lipid-based biofuels and platform chemical production. A promising, CO₂-efficient resource is autotrophically cultivated microalgae, either for direct single-cell oil (SCO) production or as a biomass substrate for fermentative SCO production via organisms like yeasts. Regarding the latter, chemical biomass hydrolysis typically results in high sugar yield and high salt concentrations due to the required neutralization prior to fermentation. In contrast, enzymatic hydrolysis is often lacking in mass efficiency. In this study, the enzymatic hydrolysis of both nutrient-replete and lipid-rich autotrophic Microchloropsis salina biomass was optimized, testing different pre-treatments and enzyme activities. Hereby, the protease treatment to weaken the cell wall integrity and the dosing of the Cellic CTec3 was identified to have the highest effect on hydrolysis efficiency. Sugar yields of 63% (nutrient-replete) and almost 100% (lipid-rich) could be achieved. The process was successfully scaled-up in mini bioreactors at a 250 mL scale. The resulting hydrolysate of the lipid-rich biomass was tested as a substrate of the oleaginous yeast Cutaneotrichosporon oleaginosus in a consumption-based acetic acid fed-batch setup. It outperformed both the model substrate and the glucose control, demonstrating the high potential of the hydrolysate as feedstock for yeast oil production. The presented sequential and circular SCO-producing value chain highlights the potential for mass- and space–time-efficient biofuel production, combining the autotrophic cultivation of oleaginous algae with decoupled yeast oil fermentation for the first time. Full article

Microalgal strains—Picochlorum costavermella VAS2.5, Picochlorum oklahomense PAT3.2B and SAG4.4, Microchloropsis gaditana VON5.3, and Nephroselmis pyriformis PAT2.7—were evaluated in an Open Pond Simulating Reactor (OPSR) under varied conditions to assess their biomass yield and high-value metabolite production. Overall, the strains produced 269.1–523.0 mg/L of biomass under balanced growth conditions in modified Artificial Seawater, continuous illumination, and pH 8.5. Phosphorus limitation notably enhanced yields for SAG4.4 and PAT2.7 (529.0 ± 52.2 mg/L and 452.2 ± 21.0 mg/L, respectively). Conversely, nitrogen limitation reduced productivity. In most strains the glycolipid plus sphingolipid fraction was dominant. Significant quantities of 20:5(n-3) were traced in the cultures of VAS2.5 and VON5.3, while the PAT3.2B and SAG4.4 strains produced considerable amounts of 18:3(n-3). In contrast, the most interesting fatty acid synthesized by PAT2.7 was 16:1(n-7), which was also detected in significant quantities in VAS2.5 and VON5.3. Polysaccharide content remained stable across conditions (10–15%), and protein levels reached 45–50% under control and phosphorus-limited environments. Pigment synthesis peaked at control conditions. Overall, the biochemical profiles of these strains revealed their potential for use primarily as feed additives in the aquaculture sector. Full article

Microalgae are a subject of interest not only for fundamental research but for various biotechnological applications as well. In this study, the ability of newly isolated strains, i.e., Picochlorum costavermella VAS2.5, Picochlorum oklahomense SAG4.4, Microchloropsis gaditana VON5.3, and Nephroselmis pyriformis PAT2.7, to grow when cultured in an open raceway pond under laboratory conditions and produce various metabolites of high-added value was evaluated. N. pyriformis PAT2.7 and P. costavermella VAS2.5 were the greatest in biomass production (exceeding 0.4 g/L), while P. costavermella VAS2.5 and M. gaditana VON5.3 were the greatest in lipid production (reaching approximately 18%, wt/wt). The lipid fraction of glycolipids and sphingolipids was predominant (43.6–55.4%, wt/wt), followed by neutral lipids (27.1–50.1%, wt/wt) and phospholipids (6.9–17.4%, wt/wt). Picochlora and M. gaditana VON5.3 lipids were rich in ^{Δ5,8,11,14,17}C20:5 and/or ^Δ9,12,15C18:3, while N. pyriformis PAT2.7 synthesized ^Δ9C16:1 in large quantities (30–40%, wt/wt). All strains showed remarkable yields in polysaccharide and protein production, demonstrated a well-balanced amino acid profile, and synthesized pigments in amounts comparable to other studies. The biochemical profiles of these strains showcased their suitability for use primarily in the aquaculture sector. Full article

Marine microalgae from the genus Nannochloropsis are promising candidates for the photoautotrophic production of eicosapentaenoic acid (EPA, C20:5), a polyunsaturated fatty acid known for its numerous health benefits. A recent study demonstrated that Microchloropsis salina can accumulate high amounts of EPA when cultivated in flat-plate gas-lift photobioreactors. This study aimed to characterize an alternative strain, Nannochloropsis oceanica, and compare its biomass and EPA productivity to M. salina. Applying simulated dynamic climate conditions of a repeated sunny summer day in Eastern Australia, N. oceanica was cultivated in LED-illuminated flat-plate gas-lift photobioreactors. The results showed significantly higher biomass growth and EPA contents compared to M. salina. An EPA productivity of 33.0 ± 0.6 mg_EPA L⁻¹ d⁻¹ has been achieved in batch processes with N. oceanica. Scaling up the photoautotrophic process to 8 m² thin-layer cascade photobioreactors resulted in doubled concentrations of N. oceanica biomass compared to laboratory-scale batch processes. This improvement was likely due to the reduced fluid layer depth, which enhanced light availability to the microalgal cells. Using urea instead of nitrate as a nitrogen source further improved the EPA production of N. oceanica in thin-layer cascade photobioreactors, achieving CDW concentrations of up to 17.7 g L⁻¹ and thus a high EPA concentration of 843 mg L⁻¹. These findings highlight N. oceanica as an alternative to M. salina for sustainable EPA production, offering potential for further industrial applications. Full article

The microalgal strains Picochlorum costavermella VAS2.5, Picochlorum oklahomense SAG4.4, Picochlorum oklahomense PAT3.2B, Microchloropsis gaditana VON5.3, and Nephroselmis pyriformis PAT2.7 were cultured in a Stirred Tank Reactor at 25 °C or 20 °C in modified artificial seawater and their biotechnological potential was assessed. VAS2.5, VON5.3, and PAT2.7 were high in biomass production at both temperatures (i.e., 438.8–671.3 mg/L and 418.4–546.7 mg/L at 25 °C and 20 °C, respectively), though P. oklahomense strains grew only at 25 °C. The highest lipid percentage was recorded for the cultures of VAS2.5 (19.3 ± 0.7%) and VON5.3 (16.4 ± 1.5%) at 25 °C, notably rich in ^{Δ5,8,11,14,17}C20:5, while PAT2.7 proved a major producer of ^Δ9C16:1. The predominant lipid fraction was glycolipids and sphingolipids (41.3–57.4%) for VAS2.5, PAT2.7 at 25 °C and VON5.3 at 20 °C and neutral lipids (55.6–63.5%) in the other cultures, indicating the different effect of temperature on lipid synthesis of the various microalgae. Additionally, almost all strains stood out for their high protein content, exceeding 50% in the culture of PAT3.2B, but polysaccharide and pigment content were not high. The biochemical profiles of the isolates showcased their suitability for use primarily as feed additives in the aquaculture sector. Full article

The marine oleaginous microalga Microchloropsis gaditana (formerly Nannochloropsis gaditana) exhibits a high capacity to thrive in a broad range of environmental conditions, being predominantly utilized as feed in aquaculture. This article reports the characterization of the culturable yeast population present during the scale-up process of M. gaditana cultivation at Necton S.A. facilities, from 5 L flasks until tubular photobioreactors. The 146 yeast isolates obtained, molecularly identified based on D1/D2 and ITS nucleotide sequences, belong to the species Rhodotorula diobovata, R. mucilaginosa, R. taiwanensis, R. sphaerocarpa, Vishniacozyma carnescens, Moesziomyces aphidis, and Meyerozyma guilliermondii. The yeast abundance was found to increase throughout upscaling stages. The yeast populations isolated from microalgal cultures and water samples share phylogenetically close isolates, indicating a possible common source. The impressive high percentage of red yeasts isolated (90%) is consistent with the recognized role of carotenoid pigments in yeast photoprotection. Sixty yeast isolates were tested for lipid (Nile Red staining) and biosurfactant (oil drop dispersion and emulsification index) production. Results revealed that these capacities are common features. Microbial lipids and biosurfactants have promising biotechnological applications. Moreover, biosurfactants can fulfill various physiological roles and provide advantages in natural environments contributing to the promising use of yeasts as probiotics in microalgae production. Full article

Sustainably farmed Atlantic salmon could drive global food system solutions by contributing essential nutrients to the human diet while delivering high-quality protein. One of the biggest obstacles to sustainable salmon aquaculture in Chile is the prevalence of piscirickettsiosis disease caused by the Gram-negative bacteria Piscirickettsia salmonis and the excessive amount of antibiotics used to eradicate this disease. Farmed salmon products can be consumed without prior processing and therefore present a substantial risk for the transfer of resistant pathogens to humans. Antibiotics also carry the risk of antibiotic residues and damage to the environment. An alternative to antibiotics is the use of natural antimicrobials without the negative influence on the consumer’s microbiome. Here, we evaluate the potential antimicrobial activity against P. salmonis of the marine microalgae Microchloropsis gaditana. A non-genetically modified M. gaditana was grown with nitrogen deprivation to improve the synthesis of the eicosapentaenoic fatty acid (EPA). A spray-dried M. gaditana concentrate (Mg) was elaborated and given to Atlantic salmon for a period of 49 days, and serum and fillet samples were collected. Our results showed a significant increase in the nutritional quality improving the levels of EPA+ Docosapentaenoic acid (DPA) (23%) and Vitamin D₃ (106%) of the fillets treated with Mg. Fish fed serum were challenged with P. salmonis, and serum antibacterial activity was measured. Sera from fish fed Mg-enriched diets showed a significant increase in antibacterial activity (85.68%) against P. salmonis. Our results indicate that Mg can be used as a viable alternative to address the critical problem of microbial resistance and to assure consumers that farm-raised Atlantic salmon is safe. Full article

The interdisciplinary nature of science, technology, engineering, and mathematics (STEM) offers the opportunity to implement educational approaches to biotechnology and process engineering issues. The focus should be on the promotion of scientific literacy in contexts relevant to research, industry, and society. This article specifically shows the development of suitable low-level experiments to provide a milestone for the implementation of biotechnological and process engineering issues in STEM education. The experiments show the successful transfer of inquiry-based bioprocess engineering experiments with a Do-It-Yourself (DIY) bioreactor and low-cost sensors. It was possible to achieve comparable trends of process-relevant state variables like mixing time and volumetric mass transfer coefficient (k_La) for the DIY bioreactor in comparison to established commercial systems. Furthermore, microalga Microchloropsis gaditana could be successfully cultivated under different cultivation conditions in the DIY system, and the respective growth curves could be observed. The DIY system is well suited for experimental application in schools and provides a scientifically substantiated basis for data interpretation. The scientific outreach approach and cooperation in a multiprofessional team for the transfer of process engineering questions to education can be evaluated as enriching. Experiments involving educational concepts offer a variety of connecting elements in the curriculum and opportunities to foster scientific literacy. Full article

Microalgae are a promising biomass source because of their capability to fixate CO₂ very efficiently. In this study, the potential of Microchloropsis salina biomass as a feedstock for fermentation was explored, focusing on biomass hydrolysis by employing various mechanical and chemical cell disruption strategies in combination with enzymatic hydrolysis. Among the mechanical cell disruption methods investigated on a lab scale, namely ultrasonication, bead milling, and high-pressure homogenization, the most effective was bead milling using stainless-steel beads with a diameter of 2 mm. In this way, 87–97% of the cells were disrupted in 40 min using a mixer mill. High-pressure homogenization was also effective, achieving 86% disruption efficiency after four passes on a 30–200 L scale using biomass with 15% (w/w) solids content. Enzymatic hydrolysis of the disrupted cells using a mixture of cellulases and mannanases yielded up to 25% saccharification efficiency after 72 h. Acidic hydrolysis of undisrupted cells followed by enzymatic treatment yielded around 30% saccharification efficiency but was coupled with significant dilution of the resulting hydrolysate. Microalgal biomass hydrolysate produced was determined to have ~8.1 g L⁻¹ sugars and 2.5% (w/w) total carbon, as well as sufficient nitrogen and phosphorus content as a fermentation medium. Full article

The use of microalgae as a food ingredient has been gaining attention in recent years due to its nutritional benefits. The main goals of this study were to (i) assess the nutritional potential of Chlorella vulgaris, Tetraselmis chuii, Microchloropsis gaditana, and Phaeodactylum tricornutum; (ii) evaluate their bioactive properties (antioxidant activity, total phenolic content, and α-amylase inhibitory activity) and (iii) assess the main volatile compounds composition. The protein content was considerably high (32–44 mg/100 g dw) for all the microalgae strains. The DPPH scavenging potential range was 14–25 mg Trolox/100 g dw (highest for T. chuii) and the ferric reducing power ability range was 13–67 µmol Trolox/dw (higher for T. chuii). The total phenolic content range was 2–7 mg of gallic acid equivalents/g dw, for M. gaditana and T. chuii, respectively, which was mainly due to the presence of catechin (1–9 µg/g dw), epicatechin (3–29 µg/g dw), and vanillic acid (1–14 µg/g dw). The ɑ-amylase inhibitory potential range was 26–42%. C. vulgaris was richer in chlorophyll a (18 mg/g dw), whilst T. chuii was particularly rich in chlorophyll b (29 mg/g dw). P. tricornutum showed the highest carotenoid content (4 mg/g dw). Aldehydes and alkanes were the major compounds identified in M. gaditana, whereas alcohols and N-based compounds existed in higher amounts in P. tricornutum. T. chuii and C. vulgaris were enriched in ketones and alkenes. This study’s novelty lies in its comprehensive and integrative analysis of the nutritional, bioactive, and volatile properties of four distinct microalgae strains. By providing detailed comparisons and highlighting potential applications in functional foods, it offers a unique contribution to the field of microalgae research and its practical application in the food industry. This multifaceted approach sets it apart from existing studies, offering new insights and opportunities for leveraging microalgae as valuable food ingredients. Full article

Lipid production using microalgae is challenging for producing low-value-added products. Harnessing microalgae for their fast and efficient CO₂ fixation capabilities may be more reasonable since algal biomass can be utilized as a precursor for various products in a biorefinery approach. This study aimed to optimize the productivity and efficiency of Microchloropsis salina biomass production in open thin-layer cascade (TLC) photobioreactors under physical simulation of suitable outdoor climate conditions, using an artificial seawater medium. Continuous operation proved to be the most suitable operating mode, allowing an average daily areal productivity of up to 27 g m⁻² d⁻¹ and CO₂ fixation efficiency of up to 100%. Process transfer from 8 m² to 50 m² TLC photobioreactors was demonstrated, but with reduced daily areal productivity of 21 g m⁻² d⁻¹ and a reduced CO₂ fixation efficiency, most probably due to increased temperatures at midday above 35 °C. An automated overnight switch-off of the circulation pumps was implemented successfully, reducing energy and freshwater requirements by ~40%. The ideal conditions for continuous production were determined to be a dilution rate of 0.150–0.225 d⁻¹, pH of 8.5, and total alkalinity of 200–400 ppm, facilitating efficient pilot-scale production of microalgal biomass in TLC photobioreactors. Full article

Marine microalgae offer a sustainable alternative source for the human diet’s essential omega-3-fatty acids, including docosahexaenoic acid (DHA, C22:6) and eicosapentaenoic acid (EPA, C20:5). However, none of them can produce DHA and EPA in a nutritionally balanced ratio of 1:1. As shown recently, the phototrophic co-cultivation of the golden-brown microalgae Tisochrysis lutea (DHA producer) with the green microalgae Microchloropsis salina (EPA producer) can provide microalgae biomass with a balanced DHA-to-EPA ratio with increased productivity compared to monocultures. This study evaluates whether other golden-brown (Isochrysis galbana) and green microalgae (Nannochloropsis oceanica, Microchloropsis gaditana) can enable the phototrophic batch production of omega-3 fatty acids in a nutritionally balanced ratio in co-culture. All co-cultivations applying a physically dynamic climate simulation of a repeated sunny summer day in Australia in LED-illuminated flat-plate gas lift photobioreactors resulted in increased biomass concentrations compared to their respective monocultures, achieving balanced DHA-to-EPA ratios of almost 1:1. Using urea instead of nitrate as a nitrogen source increased the EPA content by up to 80% in all co-cultures. Light spectra measurements on the light-adverted side of the photobioreactor showed that increased biomass concentrations in co-cultures could have been related to enhanced light use due to the utilization of different wavelengths of the two microalgae strains, especially with the use of green light (500–580 nm) primarily by golden-brown microalgae (I. galbana) and orange light (600–620 nm) predominantly used by green microalgae (N. oceanica). Phototrophic co-cultivation processes thus promise higher areal biomass yields if microalgae are combined with complimentary light-harvesting features. Full article

Non-concentrated algae storage can bridge the period between algae harvesting and processing while avoiding the stress conditions associated with the concentration step required for concentrate storage. This study aimed to examine organic matter losses during the non-concentrated storage of Microchloropsis gaditana at pilot-scale. Algae cultures (400–500 L) were stored for up to 12 days either at an 8 °C target temperature or at 19 °C as the average temperature. The centrifugation yield of stored algal cultures decreased from day 5 or day 8 onwards for all storage conditions. After 12 days, the centrifugation yields were between 57% and 93% of the initial yields. Large differences in centrifugation yields were noted between the algae batches. The batch-to-batch difference outweighed the effect of storage temperature, and the highest yield loss was observed for the 8 °C cooled algae batch. The analysis of stored algae before and after centrifugation suggested that the decreasing yields were not related to respiration losses, but rather, the decreasing efficiency with which organic matter is collected during the centrifugation step. Full article

The snail Bellamya purificata is recognized as a potential bio-remediation species, and is commonly employed in polyculture to enhance resource utilization efficiency and realize culture environment regulation. In order to enrich the microbiome studies on elucidating the ecological effects of snail B. purificata farming, we assessed the effect of B. purificata farming activities, at varying stocking densities, on the algal and fungal communities in sediment. Four experimental groups were established in our study, each corresponding to a different stocking density: 0, 234.38, 468.75, and 937.5 g/m², represented as CON, LD, MD, and HD, respectively. High-throughput sequencing based on ITS and 23S ribosomal RNA (rRNA) genes was employed to analyze the variations in algal and fungal communities under B. purificata farming activities at different stocking densities. B. purificata farming activities had no significant effect on the alpha diversities of fungal and algal communities, but significantly altered the compositions of fungal and algal communities in sediments, especially B. purificata farming activity at low stocking density. B. purificata farming activities at low stocking density could significantly increase the relative abundances of fungal genera Paraconiothyrium and Penicillium compared with the CON group. The promoting effect diminished with increasing density. B. purificata farming activities at low or medium stocking density also could enhance the relative abundances of algal genera Microchloropsis, Scenedesmus, and Auxenochlorella. Hence, B. purificata farming activity at low stocking density might be the optimum density to enhance resource utilization efficiency and minimize environmental pollution. Full article