•A 100g.L−1 slurry of Nannochloropsis gaditana was submitted to cell disruption.•Multiple cell disruption methods were screened on the slurry.•High-pressure homogenization and bead milling were the ...most efficient.•Pulsed Electric Field was the least efficient on all levels.•The lowest energy cost per unit of released protein was obtained with HPH.•The mathematical model corresponds to the experimental data of HPH and bead milling.
Several cell disruption methods were tested on Nannochloropsis gaditana, to evaluate their efficiency in terms of cell disintegration, energy input and release of soluble proteins. High-pressure homogenization (HPH) and bead milling were the most efficient with >95% cell disintegration, ±50% (w/w) release of total proteins and low energy input (<0.5kWh.kg−1biomass). Enzymatic treatment required low energy input (<0.34kWh.kg−1biomass), but it only released ±35% protein (w/w). Pulsed Electric Field (PEF) was neither energy-efficient (10.44kWh.kg−1biomass) nor successful for protein release (only 10% proteins w/w) and cell disintegration. The release of proteins after applying HPH and bead milling always required less intensive operating conditions for cell disruption. The energy cost per unit of released protein ranged from 0.15–0.25 €.kgProtein−1 in case of HPH, and up to 2–20 €.kgProtein−1 in case of PEF.
Display omitted
•Soluble proteins from the green alga Tetraselmis suecica were extracted.•The extraction process was mild and simple (one step), requiring low energy input.•Protein enrichment was ...achieved by controlling the bead milling time.•The crude protein extract showed excellent surface activity and gelation behaviour.•The functionality of the alga extract was superior to whey protein isolates.
The use of a single controlled bead milling step of the microalga Tetraselmis suecica resulted in a soluble fraction, rich in functional proteins. This was achieved by fine-tuning the processing time, thereby exploiting the difference in rates of protein and carbohydrate release during milling. Soluble proteins were extracted under mild conditions -room temperature, no addition of chemicals, pH 6.5-, with a yield of 22.5% and a specific energy consumption of 0.6 kWh kgDW−1, which is within the recommended minimum energy for an extraction step in a biorefinery process. The resulting protein extract contained 50.4% (DW) of proteins and 26.4% carbohydrates, showed light green color and displayed superior surface activity and gelation behavior compared to whey protein isolate. The proposed process is simple (only one bead milling step), scalable, and allows the mild extraction of functional proteins, making it interesting for industrial applications in the food industry.
The fatty acid content of microalgae, especially the high content of omega-3 fatty acids such as eicosapentaenoic acid (EPA, C20:5) and docosahexaenoic acid (DHA, C22:6), could enrich eggs when fed ...to laying hens. Moreover, the properties and bioactive components of omega-3 fatty acids could positively influence the health and production performance of laying hens. In this study, the effects of dried Nannochloropsis limnetica inclusions in diets on yolk omega-3 fatty acid content, laying hen performance, nutrient retention, intestinal morphometry and systemic inflammatory markers were measured. A total of 240 twenty-five-wk-old laying hens were randomly assigned to 5 treatments distributed among 30 pens. Treatment A received the reference diet, while diets in treatments B, C, and D contained the control diet with 1, 2, and 3% microalgae added, respectively. In treatment E, a portion of ingredients of the control diet was replaced with rapeseed meal to induce a mild nutritional challenge, along with an inclusion of 3% microalgae. Compared to the control group the rate of lay increased by approximately 5% (P = 0.039) when birds were fed 2 or 3% microalgae. Furthermore, inclusion of 2 and 3% microalgae resulted in higher feed intake compared to the control group (126, 125, and 119 g/hen/d respectively; P = 0.001). Other performance parameters such as nutrient retention and egg characteristics were not affected by the dietary treatments. The EPA and DHA content of the yolk increased with increasing microalgae inclusion level (P < 0.001). A 2% algal inclusion resulted in 58.3 (EPA) and 603 (DHA) mg per 100 g dry yolk, respectively. Plasma haptoglobin levels of laying hens in both treatments receiving 3% microalgae were almost 3 times lower compared to the control group (1.25 and 1.62 vs. 5.60; P < 0.001), regardless of the inclusion of rapeseed in the diet. Based on these results, it can be concluded that the inclusion of N. limnetica enriches the egg yolk without negatively affecting the performance of laying hens and egg characteristics. Due to the positive effect on feed intake, microalgae in the diet provide nutritional benefits for laying hens. However, the positive effects of microalgae, especially on the health of laying hens, warrants further research.
Schematic representation of the overall process from cell disruption to diafiltration.
Display omitted
•A 100g.L−1 slurry of N. gaditana was submitted to protein biorefinery.•A biorefinery process ...was tested to disrupt the cell wall and filtrate the samples.•High-pressure homogenization was more efficient than enzymatic treatment.•The filtration process was more efficient after enzymatic treatment.•Increasing the cut off of the membrane does not improve the filtration process.•The mathematical model corresponded to the experimental data of filtration.
A mild biorefinery process was investigated on the microalga Nannochloropsis gaditana, to obtain an enriched fraction of water soluble proteins free from chlorophyll. After harvesting, a 100g.L−1 solution of cells was first subjected to cell disruption by either high-pressure homogenization (HPH) or enzymatic treatment (ENZ). HPH resulted in a larger release of proteins (49%) in the aqueous phase compared to the Alcalase incubation (35%). In both cases, an ultrafiltration/diafiltration (UF/DF) was then performed on the supernatant obtained from cell disruption by testing different membrane cut-off (1000kDa, 500kDa and 300kDa). After optimising the process conditions, the combination of ENZ→UF/DF ended in a larger overall yield of water soluble proteins (24.8%) in the permeate compared to the combination of HPH→UF/DF (17.4%). A gel polarization model was implemented to assess the maximum achievable concentration factor during ultrafiltration and the mass transfer coefficient related to the theoretical permeation flux rate.
•Marine water microalga grown under nitrogen stress was the most resistant.•The release of lipids followed the “hindered molecule diffusion phenomenon”•Marine stressed microalga released the lowest ...amount of proteins.•The enzymatic treatment was efficient enough to release most of the proteins.•Marine stressed microalga required high energy input to release proteins.
The impact of four different growth conditions on the cell disruption efficiency of Neochloris oleoabundans was investigated. A mechanical and biological cell disruption methods were evaluated separately and combined. It has been established that microalgae grown in marine water under nitrogen deprivation were the most resistant against cell disruption methods and released the lowest amount of proteins. The release of lipids, however, followed the “hindered molecule diffusion phenomenon” because it did not follow the same release pattern as proteins. The enzymatic treatment was efficient enough to release the majority of the proteins without combining it with high-pressure homogenization. Regarding energy input, Neochloris oleoabundans grown in marine water under nitrogen deprivation required the highest energy input to release proteins (Ep = 13.76 kWh.kg−1) and to break the cells by high-pressure homogenization (Ex – HPH = 1.14 kWh.kg−1) or by the combination of enzymes and High-pressure homogenization (Ex – ENZ = 2.79 kWh.kg−1).
A mild fractionation process to extract functional biomolecules from green microalgae was implemented. The process includes bead milling, centrifugation, and filtration with several membrane ...cut-offs. For each fraction, the corresponding composition was measured, and the surface activity and gelation behavior were determined. A maximum protein yield of 12% was obtained in the supernatant after bead milling and between 3.2 and 11.7% after filtration. Compared to whey protein isolate, most of the algae fractions exhibited comparable or enhanced functionality. Surface activity for air–water and oil–water interfaces and gelation activities were notably superior for the retentate fractions compared to the permeates. It is proposed that such functionality in the retentates is due to the presence of hydrophobic compounds and molecular complexes exhibiting a similar behavior as Pickering particles. We demonstrated that excellent functionality can be obtained with crude fractions, requiring minimum processing and, thus, constituting an interesting option for commercial applications.
Docosahexaenoic acid (DHA) is a polyunsaturated fatty acid composed of 22 carbon atoms and six double bonds. Because the first double bond, as counted from the methyl terminus, is at position three, ...DHA belongs to the so-called omega-3 group. In recent years, DHA has attracted much attention because of its beneficial effect on human health. At present, fish oil is the major source of DHA, but alternatively it may be produced by use of microorganisms. Marine microorganisms may contain large quantities of DHA and are considered a potential source of this important fatty acid. Some of these organisms can be grown heterotrophically on organic substrates without light. These processes can be well controlled and DHA with constant quality can be produced all year round. This paper reviews recent advances in the biotechnological production of DHA by marine microorganisms.
Micro-algae are a new and promising source of nutrients. The main products obtainable are dried algae with high nutrients content and high-value compounds such as fatty acids, pigments and ...anti-oxidants. This paper analyses the market and the economic opportunities of micro-algae-based food and feed sectors in the EU through an integrated methodology composed by literature search, interviews to experts and Delphi survey. Results show that the quantities produced and the market size of nutrients obtained from micro-algae are still significantly smaller in comparison to the ones derived from cereals and other commodity crops, but that the sector has seen an impressive and unique growth. Despite the challenges due to the climatic conditions together with the insufficient domestic demand and the complexity of the EU Novel Food regulation, the survey revealed that the EU can improve its market position in the next decade, thanks to its scientific and technological capacity and its dominant position in the global agri-food markets. New micro-algae-based products can be developed for foreign markets, and the improved global production share of European firms (presently of about 5%) may be the result of strategic acquisitions of foreign companies.
•Micro-algae are considered an alternative source of high-value nutrients.•Their production is not yet able to contribute to food security but is growing.•Production in the EU is limited due to climatic, economic and regulatory issues.•The EU can nonetheless become market leader in the next decade.•The EU's strengths are its technological capacity and the agri-food markets.
The heterotrophic marine microalga Crypthecodinium cohnii produces docosahexaenoic acid (DHA), a polyunsaturated fatty acid with food and pharmaceutical applications. So far, DHA production has been ...studied with glucose and acetic acid as carbon sources. This study investigates the potential of ethanol as an alternative carbon source for DHA production by C. cohnii. In shake-flask cultures, the alga was able to grow on ethanol. The specific growth rate was optimal with 5 g l-1 ethanol and growth did not occur at 0 g l-1 and above 15 g l-1. By contrast, in fed-batch cultivations with a controlled feed of pure ethanol, cumulative ethanol addition could be much higher than 15 g l-1, thus enabling a high final cell density and DHA production. In a representative fed-batch cultivation of C. cohnii with pure ethanol as feed, 83 g dry biomass l-1, 35 g total lipid l-1 and 11.7 g DHA l-1 were produced in 220 h. The overall volumetric productivity of DHA was 53 mg l-1 h-1, which is the highest value reported so far for this alga.
Because biomass is a widely available, renewable resource, its utilisation for the production of energy has great potential for reducing CO(2) emissions and thereby preventing global warming. In this ...mini-review the 'state of the art' of several fermentation processes is discussed, starting with the most advanced process of ethanol production. This is followed by methane production, an established process for waste water purification which is gaining more attention because of the inherent energy production. Subsequently ABE fermentation is discussed and finally the biological production of hydrogen. The last section proposes a new way to assess and compare the different processes by relating their merit to 'work content' values and 'lost work' instead of the combustion values of their products. It is argued that, especially when dealing with energy from biomass, the application of this methodology will provide a uniform valuation for different processes and products. The described fermentation processes enable the supply of pure energy carriers, either gaseous or liquid, from biomass, yet the introduction of these processes is hampered by two major problems. The first is related to technological shortcomings in the mobilisation of fermentable components from the biomass. The second, having a much greater impact, is linked with socio-economics: until full externality costs are attributed to fossil fuels, accounting for their role in pollution and global warming, the competitiveness of the processes described here will hardly stand a chance.