Relative stabilities of microalgal carotenoids in microalgal extracts, biomass and fish feed: effect of storage conditions

Effects of pasteurization on set yogurt fortified with astaxanthin-rich yolk: Evaluation of physicochemical properties, stability, and biological activity

Pasteurization usually has a large influence on yogurt and astaxanthin. This study aimed to investigate the effects of 3 pasteurization methods, including low-temperature, long-time treatment at 63°C for 30 min (LTLT-1) and 65°C for 30 min (LTLT-2), and high-temperature, short-time treatment at 75°C for 15 s (HTST), on the physicochemical properties, stability, and biological activity of set yogurt fortified with astaxanthin-rich yolk. The results showed that the LTLT-2 group had a higher astaxanthin retention, with no significant difference from the LTLT-1 group. The in vitro digestion results also confirmed that LTLT-2 had a high free radical scavenging capacity. Temperatures between 63°C and 65°C are within a safe range for preventing significant heat degradation of astaxanthin. Over the 21-d storage period, LTLT-2 significantly outperformed LTLT-1 and HTST regarding texture and particle size. This work demonstrates that the pasteurization conditions of 65°C for 30 min could be used to prepare a functional set yogurt with stable quality and antioxidant activity.

Astaxanthin: a nature's versatile compound utilized for diverse applications and its therapeutic effects

Astaxanthin (ASTX), red-colored xanthophyll, also known as the "king of carotenoids" exhibits a strong antioxidant property that can be naturally found in green algae Haematococcus pluvialis, red yeast Phaffia rhodozyma, and various aquatic species including salmon, krill, trout, and fish eggs. Due to their strong antioxidant qualities, ASTX nanoparticles may be crucial in fighting against phytotoxicity caused by heavy metal ions. Similarly, it may also reduce the uptake of heavy metal, i.e. cadmium, and translocation by improving the morpho-physiological profiles of plants. Furthermore, it can also have the ability to scavenge free radicals, therefore, it can protect plants from reactive oxygen species (ROS). Implementing ASTX nanoparticles on crops can also help to achieve higher food production while minimizing toxic effects. Additionally, it can also possess several therapeutic activities including anti-cancerous, anti-diabetic, antioxidant, anti-aging, anti-inflammation, hepatoprotective, and cardiovascular, etc. that can be beneficial to treat various types of diseases in humans and animals. Recently, it has gained more interest in food, agriculture, aquaculture, neutraceuticals, and pharmaceutical industries due to its wide range of applications including food-coloring agents, food supplements, and strong antioxidant property that helps in skin protection, and boosts immune function. However, ASTX possesses poor water solubility and chemical stability so the implementation of ASTX on human health is facing various issues. Therefore, nanoencapsulation of ASTX is very crucial to improve its chemical stability and solubility, ultimately leading to its bioavailability and bioaccessibility. Recently, ASTX has been commercially available with specific dosages in the market mainly in the form of tablets, gels, powders, creams, syrups, etc. The current review mainly highlights the present state of ASTX nanoparticle applications in various fields explaining its natural and synthetic sources, extraction methods, chemical structure, stability, nanoformulations, nano encapsulation, and various commercial aspects.

Utilizing Haematococcus pluvialis to simulate animal meat color in high-moisture meat analogues: Texture quality and color stability

The effect of Haematococcus pluvialis (HP) (0.25∼1.25 %) as a colorant during high moisture extrusion (50 %) on the texture and microstructural properties of soy protein-based high moisture meat analogs (HMMA) was evaluated. Furthermore, the stability of HP-induced meat like color of the HMMA as a function of light exposure, freeze/thawing, frozen storage and cooking temperature and duration was investigated. The addition of HP reduced the elasticity of HMMA but enhanced its hardness, chewiness, and resilience. HP addition at low levels promoted the flexible and disordered regions within the protein secondary structure while excessive HP addition was unfavorable for protein cross-linking. The optimal degree of texturization was achieved with 0.75 % HP. Sensory evaluations revealed that HMMA with 1 %HP had a color similar to fresh beef sirloin, while HMMA with 0.25 % HP had a color closer to fresh pork loin. Light exposure induced the greatest color loss of the meat analogs compared with the cooking and frozen storage. The a* value of HMMA containing 1.25 % HP decreased by 30 % during the 14 days of light exposure. Frozen storage at darkness efficiently preserved the meat-like color of the extrudates. Overall, HP was found as promising colorant for HMMA production but the storage condition of the extrudates should be carefully optimized.

Oxidative stability of lutein on exposure to varied extrinsic factors

Pre-processing treatments performed on lutein sources can cause it to degrade, generating superfluous metabolites and lowering lutein's bioactivity. However, evidences suggesting extent of reduction in functional stability of lutein on exposure to such treatment conditions are nil. This study is first of its kind, where we attempted to gain clarity on the extent of degradation caused by the changes in temperature (40-100 °C), pH (2-8) and duration of such treatments. Increase (3.9 folds) in lutein loss within an hour at 40 °C occurred when pH was lowered from 8 to 2. Increase (1.7 folds) in lutein loss at neutral pH and 40 °C occurred when duration of exposure was increased from 1 to 4 h. Besides, lutein loss significantly increased on rising the temperature by every 10 °C. The functional stability of lutein in relation to its degradation was also studied by monitoring its radical scavenging activity. While lutein is highly unstable, lutein structure and its respective bioactivity can be significantly (p < 0.05) retained (< 12.44% and > 54.87% respectively) by maintaining the operating conditions at higher pH (7-8) and lower temperatures (40-50 °C) for a short period of time (< 1 h).

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-022-05430-3.

Bio-membrane integrated systems for nitrogen recovery from wastewater in circular bioeconomy

Wastewater contains a significant amount of recoverable nitrogen. Hence, the recovery of nitrogen from wastewater can provide an option for generating some revenue by applying the captured nitrogen to producing bio-products, in order to minimize dangerous or environmental pollution consequences. The circular bio-economy can achieve greater environmental and economic sustainability through game-changing technological developments that will improve municipal wastewater management, where simultaneous nitrogen and energy recovery are required. Over the last decade, substantial efforts were undertaken concerning the recovery of nitrogen from wastewater. For example, bio-membrane integrated system (BMIS) which integrates biological process and membrane technology, has attracted considerable attention for recovering nitrogen from wastewater. In this review, current research on nitrogen recovery using the BMIS are compiled whilst the technologies are compared regarding their energy requirement, efficiencies, advantages and disadvantages. Moreover, the bio-products achieved in the nitrogen recovery system processes are summarized in this paper, and the directions for future research are suggested. Future research should consider the quality of recovered nitrogenous products, long-term performance of BMIS and economic feasibility of large-scale reactors. Nitrogen recovery should be addressed under the framework of a circular bio-economy.

Enzymatic acylation of lutein with a series of saturated fatty acid vinyl esters and the thermal stability and anti-lipid oxidation properties of the acylated derivatives

Lutein was enzymatically acylated with saturated fatty acid vinyl esters of different lengths of carbon chain (C₆ -C₁₄ ) under the action of Candida antarctica lipase B (Novozyme 435). The acylation reaction was optimized by considering substrate molar ratio, reaction solvent, type of enzyme, and reaction time. The highest yield (88%) was obtained using the Novozyme 435 to catalyze the acylation reaction of lutein and vinyl decanoate (lutein/vinyl decanoate molar ratio of 1/10) for 16 h in methyl tert-butyl ether. Ten lutein esters were synthesized, isolated, and purified, which were characterized by Fourier-transform infrared spectroscopy, high-resolution mass spectrometry, and nuclear magnetic resonance spectroscopy. We found that the acylation of lutein improved its antioxidant capacity in lipid system and thermal stability. Our study extended the potential application of lutein in lipophilic food, cosmetic, and pharmaceutical industries. Practical Application: Enzyme acylation of lutein improved its antioxidant capacity in lipid system and thermal stability, extended its potential application in food, cosmetic, and pharmaceutical industries. In addition, our study also provided a new perspective and cognition for the further development and utilization of lutein.

Biochemical and Immunological implications of Lutein and Zeaxanthin

Throughout history, nature has been acknowledged for being a primordial source of various bioactive molecules in which human macular carotenoids are gaining significant attention. Among 750 natural carotenoids, lutein, zeaxanthin and their oxidative metabolites are selectively accumulated in the macular region of living beings. Due to their vast applications in food, feed, pharmaceutical and nutraceuticals industries, the global market of lutein and zeaxanthin is continuously expanding but chemical synthesis, extraction and purification of these compounds from their natural repertoire e.g., plants, is somewhat costly and technically challenging. In this regard microbial as well as microalgal carotenoids are considered as an attractive alternative to aforementioned challenges. Through the techniques of genetic engineering and gene-editing tools like CRISPR/Cas9, the overproduction of lutein and zeaxanthin in microorganisms can be achieved but the commercial scale applications of such procedures needs to be done. Moreover, these carotenoids are highly unstable and susceptible to thermal and oxidative degradation. Therefore, esterification of these xanthophylls and microencapsulation with appropriate wall materials can increase their shelf-life and enhance their application in food industry. With their potent antioxidant activities, these carotenoids are emerging as molecules of vital importance in chronic degenerative, malignancies and antiviral diseases. Therefore, more research needs to be done to further expand the applications of lutein and zeaxanthin.

Effect of storage on plant biostimulant and bioactive properties of freeze-dried Chlorella vulgaris biomass

Microalgae are potential plant biostimulants and biocontrol agents. A major hurdle towards their commercialization is the production of large volumes of biomass at the correct time of year. Secondary metabolites are unstable and the "shelf-life" of bioactive microalgal biomass needs to be investigated. The aim of the study was to investigate the effects of storage conditions on freeze-dried microalgae to determine how long the biomass retained its growth promoting and bioactive properties under various temperature and light conditions. Chlorella vulgaris biomass was stored in the dark at - 70 °C, 10 °C, and 25 °C and in the light at 25 °C. Samples were tested every 3-4 months for 15 months. Storage time significantly influenced the rate of change in the bioactivity in the C. vulgaris biomass with storage temperature also having some effect. Rooting activity decreased in the mungbean rooting assay over time up to 12 months and then increased slightly. Antimicrobial activity increased against Staphylococcus aureus and Escherichia coli for up to 12 months and then declined. Antioxidant activity measured in the DPPH assay remained relatively stable for up to 12 months and then significantly decreased with longer storage. The change in bioactivity over time was attributed to the gradual breakdown of the rigid cell wall of C. vulgaris, thereby improving extraction efficiency but exposing the secondary metabolites to oxygen, thus quickening their degradation. Biomass produced for commercial purposes requires preliminary validation as the results of the present study showed that bioactive compounds are susceptible to degradation over time.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10811-021-02596-9.

Aquaculture wastewater treatment through microalgal. Biomass potential applications on animal feed, agriculture, and energy

The use of microalgae to remediate raw effluent from brown crab aquaculture was evaluated by performing batch mode growth tests using separately the microalgae Chlorella vulgaris (Cv), Scenedesmus obliquus (Sc), Isochrysis galbana (Ig), Nannocloropsis salina (Ns), and Spirulina major (Sp). Removal efficiencies in batch growth were 100% for total nitrogen and total phosphorus for all microalgae. Chemical oxygen demand (COD) remediations were all above 72%. Biomass productivity varied from 20.9 mg L^-1 day^-1 (N. salina) to 146.4 mg L^-1 day^-1 (C. vulgaris). The two best performing algae were C. vulgaris and S. obliquus and they were tested in semi-continuous growth, reaching productivities of 879.8 mg L^-1 day^-1 and 811.7 mg L^-1 day^-1, respectively. The bioremediation of the effluent was tested with a transfer system consisting of three independent containers and compared with the use of a single container. The single container had the same capacity and received weekly the same volume of effluent as the three containers together. The remediation capacity of the 3 containers was much higher than the single one. The supplementation with NaNO₃ was tested to improve the nutrient removal microalgae' capacity, with positive results. The removal efficiencies were 100% for total nitrogen and total phosphorus and higher than 96% for COD. The obtained C. vulgaris and S. obliquus biomass were composed of 31 and 35% proteins, 6 and 8% lipids, 39 and 30% carbohydrates, respectively. The composition of these biomass suggest that it can be used as novel and sustainable ingredients in aquaculture feeds. The algal biomass of Cv and Sc were used as biostimulants in the germination of wheat and watercress, and very promising results were attained, with increases in the germination index for Cv and Sc of 175% and 48% in watercress and 84% and 98% in wheat, respectively. The biomasses of Cv and Sc were also subjected to a torrefaction process with 72.5 ± 1.7% char yields. The obtained biochars were tested as biostimulants for germination seeds (wheat and watercress) and as bio-adsorbent of dye solutions.

Production of carotenoids by microalgae: achievements and challenges

Carotenoids are a wide group of lipophylic isoprenoids synthesized by all photosynthetic organisms and also by some non-photosynthetic bacteria and fungi. Animals, which cannot synthesize carotenoids de novo, must include them in their diet to fulfil essential provitamin, antioxidant, or colouring requirements. Carotenoids are indispensable in light harvesting and energy transfer during photosynthesis and in the protection of the photosynthetic apparatus against photooxidative damage. In this review, we outline the factors inducing carotenoid accumulation in microalgae, the knowledge acquired on the metabolic pathways responsible for their biosynthesis, and the recent achievements in the genetic engineering of this pathway. Despite the considerable progress achieved in understanding and engineering algal carotenogenesis, many aspects remain to be elucidated. The increasing number of sequenced microalgal genomes and the data generated by high-throughput technologies will enable a better understanding of carotenoid biosynthesis in microalgae. Moreover, the growing number of industrial microalgal species genetically modified will allow the production of novel strains with enhanced carotenoid contents.

Potential for green microalgae to produce hydrogen, pharmaceuticals and other high value products in a combined process

Green microalgae for several decades have been produced for commercial exploitation, with applications ranging from health food for human consumption, aquaculture and animal feed, to coloring agents, cosmetics and others. Several products from green algae which are used today consist of secondary metabolites that can be extracted from the algal biomass. The best known examples are the carotenoids astaxanthin and β-carotene, which are used as coloring agents and for health-promoting purposes. Many species of green algae are able to produce valuable metabolites for different uses; examples are antioxidants, several different carotenoids, polyunsaturated fatty acids, vitamins, anticancer and antiviral drugs. In many cases, these substances are secondary metabolites that are produced when the algae are exposed to stress conditions linked to nutrient deprivation, light intensity, temperature, salinity and pH. In other cases, the metabolites have been detected in algae grown under optimal conditions, and little is known about optimization of the production of each product, or the effects of stress conditions on their production. Some green algae have shown the ability to produce significant amounts of hydrogen gas during sulfur deprivation, a process which is currently studied extensively worldwide. At the moment, the majority of research in this field has focused on the model organism, Chlamydomonas reinhardtii, but other species of green algae also have this ability. Currently there is little information available regarding the possibility for producing hydrogen and other valuable metabolites in the same process. This study aims to explore which stress conditions are known to induce the production of different valuable products in comparison to stress reactions leading to hydrogen production. Wild type species of green microalgae with known ability to produce high amounts of certain valuable metabolites are listed and linked to species with ability to produce hydrogen during general anaerobic conditions, and during sulfur deprivation. Species used today for commercial purposes are also described. This information is analyzed in order to form a basis for selection of wild type species for a future multi-step process, where hydrogen production from solar energy is combined with the production of valuable metabolites and other commercial uses of the algal biomass.

Functional properties of carotenoids originating from algae

Carotenoids are isoprenoid molecules which are synthesised de novo by photosynthetic plants, fungi and algae and are responsible for the orange, yellow and some red colours of various fruits and vegetables. Carotenoids are lipophilic compounds, some of which act as provitamins A. These compounds can be divided into xanthophylls and carotenes. Many macroalgae and microalgae are rich in carotenoids, where these compounds aid in the absorption of sunlight. Industrially, these carotenoids are used as food pigments (in dairy products, beverages, etc.), as feed additives, in cosmetics and in pharmaceuticals, especially nowadays when there is an increasing demand by consumers for natural products. Production of carotenoids from algae has many advantages compared to other sources; for example, their production is cheap, easy and environmentally friendly; their extraction is easier, with higher yields, and there is no lack of raw materials or limited seasonal variation. Recently, there has been considerable interest in dietary carotenoids with respect to their antioxidant properties and their ability to reduce the incidence of some chronic diseases where free radicals are involved. Possibly, carotenoids protect cells from oxidative stress by quenching singlet oxygen damage with various mechanisms. Therefore, carotenoids derived from algae could be a leading natural resource in the research for potential functional ingredients.

Effect of brown seaweed lipids on fatty acid composition and lipid hydroperoxide levels of mouse liver

Brown seaweed lipids from Undaria pinnatifida (Wakame), Sargassum horneri (Akamoku), and Cystoseira hakodatensis (Uganomoku) contained several bioactive compounds, namely, fucoxanthin, polyphenols, and omega-3 polyunsaturated fatty acids (PUFA). Fucoxanthin and polyphenol contents of Akamoku and Uganomoku lipids were higher than those of Wakame lipids, while Wakame lipids showed higher total omega-3 PUFA content than Akamoku and Uganomoku lipids. The levels of docosahexaenoic acid (DHA) and arachidonic acid (AA) in liver lipids of KK-A(y) mouse significantly increased by Akamoku and Uganomoku lipid feeding as compared with the control, but not by Wakame lipid feeding. Fucoxanthin has been reported to accelerate the bioconversion of omega-3 PUFA and omega-6 PUFA to DHA and AA, respectively. The higher hepatic DHA and AA level of mice fed Akamoku and Uganomoku lipids would be attributed to the higher content of fucoxanthin of Akamoku and Uganomoku lipids. The lipid hydroperoxide levels of the liver of mice fed brown seaweed lipids were significantly lower than those of control mice, even though total PUFA content was higher in the liver of mice fed brown seaweed lipids. This would be, at least in part, due to the antioxidant activity of fucoxanthin metabolites in the liver.

Stability of carotenoids in Scenedesmus almeriensis biomass and extracts under various storage conditions

Scenedesmus almeriensis biomass is a source of carotenoids, particularly lutein, and is considered to be promising as an alternative source to marigold. One key question concerning alternative sources of lutein is the loss of carotenoids that takes place between harvesting and processing, which in the case of marigold is frequently up to 50%. The work described here involved a study into the stability of the main carotenoids (lutein, violaxanthin, and beta-carotene), as well as other components, under different storage conditions. The experiments were carried out with biomass in three forms: frozen, freeze-dried, and spray-dried. The stability of extracts of Scenedesmus biomass in acetone and olive oil was also studied. The results show that the most important factor in retaining carotenoids is a low temperature. At -18 degrees C the loss of carotenoids was negligible after the storage period, regardless of the biomass form used (frozen, freeze-dried, or spray-dried). On the other hand, the carotenoid content and fatty acid profile was increasingly affected with increasing temperature. However, the protein content is unaffected by storage conditions.

Effects of magnetic field on the antioxidant defense system of recirculation-cultured Chlorella vulgaris

Little is known about the influence of magnetic fields (MF) on growth of microalgae such as Chlorella vulgaris, which has been consumed as health food for various nutritional and pharmacological effects. This preliminary study investigated whether static MF can modulate the antioxidant system in C. vulgaris by exposing the cells to static MF generated by dual yoke electromagnets with magnetic flux density of 10-50 mT for 12 h. After exposure to 10-35 mT for 12 h, the activity of superoxide dismutases and peroxidase increased significantly compared to control cells. However, a remarkable increase of catalase activity occurred at 45 and 50 mT. The lipid peroxidation of algae cells determined by production of thiobarbituric acid-reactive substances was much increased when exposed to 35, 45, and 50 mT of MF. The scavenging ability of 2,2-diphenyl-1-picrylhydrazyl radical was decreased markedly while there was no variation of total carotenoids content in C. vulgaris cells. Assay of specific growth rate in 72 h cultivation after MF exposure was also conducted. In groups after exposure to 10-35 mT of MF, specific growth rate was significantly increased. These results suggest that 10-35 mT of static MF exposure could promote the growth of C. vulgaris and regulate its antioxidant defense system to protect cells efficiently, which could possibly enhance the growth of C. vulgaris in industrialized cultivation by MF.

Spectroscopic, stability and radical-scavenging properties of a novel pigment from gardenia

A novel pigment, named gardecin, has been isolated from gardenia fruits, together with another five known crocins. The pigment, which possessed a structure which is unique among crocins, was characterised using spectrometric techniques, particularly 1D and 2D NMR. The NMR assignments were based on data from (1)H NMR, (13)C NMR, DEPT, (1)H-(1)H COSY, NOESY, HMQC and HMBC measurements. The five known crocins were identified on the basis of MS, UV/visible and 1D NMR data. Chemical stability and antioxidant ability of gardecin in comparison with the other five crocins were studied. The stronger DPPH free radical-scavenging ability of gardecin compared, with the other crocins, was observed. Kinetic studies have shown that all crocins were unstable under various conditions, but surprisingly gardecin was fairly stable.

Commercial applications of microalgae

The first use of microalgae by humans dates back 2000 years to the Chinese, who used Nostoc to survive during famine. However, microalgal biotechnology only really began to develop in the middle of the last century. Nowadays, there are numerous commercial applications of microalgae. For example, (i) microalgae can be used to enhance the nutritional value of food and animal feed owing to their chemical composition, (ii) they play a crucial role in aquaculture and (iii) they can be incorporated into cosmetics. Moreover, they are cultivated as a source of highly valuable molecules. For example, polyunsaturated fatty acid oils are added to infant formulas and nutritional supplements and pigments are important as natural dyes. Stable isotope biochemicals help in structural determination and metabolic studies. Future research should focus on the improvement of production systems and the genetic modification of strains. Microalgal products would in that way become even more diversified and economically competitive.