Operational and economic aspects of Spirulina-based biorefinery

Research progress and application of carbon sequestration in industrial flue gas by microalgae: A review

Global warming caused by the emission of CO2 in industrial flue gas has attracted more and more attention. Therefore, to fix CO2 with high efficiency and environmentally friendly had become the hot research field. Compared with the traditional coal-fired power plant flue gas emission reduction technology, carbon fixation and emission reduction by microalgae is considered as a promising technology due to the advantages of simple process equipment, convenient operation and environmental protection. When the flue gas is treated by microalgae carbon fixation and emission reduction technology, microalgae cells can fix CO2 in the flue gas through photosynthesis, and simultaneously absorb NOx and SOx as nitrogen and sulfur sources required for growth. Meanwhile, they can also absorb mercury, selenium, arsenic, cadmium, lead and other heavy metal ions in the flue gas to obtain microalgae biomass. The obtained microalgae biomass can be further transformed into high value-added products, which has broad development prospects. This paper reviews the mechanisms and pathways of CO2 sequestration, the mechanism and impacts of microalgal emission reduction of flue gas pollutants, and the applications of carbon sequestration in industrial flue gas by microalgae. Finally, this paper provides some guidelines and prospects for the research and application of green emission reduction technology for industrial flue gas.

Sustainable algal proteins, novel extraction techniques and applications in the bakery, dairy and pharmaceutical industries: A comprehensive review

Microalgae have emerged as favorable substitutes for traditional animal-based proteins in the search for sustainable protein sources. Despite being underexplored, microalgae offer the possibility of large-scale protein production via novel extraction techniques. This review synthesizes current knowledge on microalgal proteins, shedding light on their novel extraction techniques and techno-functional properties, which are still in the early stages of exploration. Additionally, it explores the miscellaneous applications of algae proteins across various industrial sectors, including bakery, dairy, pharmaceuticals, and nutrition. By discussing the techno-functional properties of algae proteins and peptides, this review underscores their potential to revolutionize the industrial landscape while addressing sustainability challenges. As research in this field progresses, microalgae are poised to emerge as a viable and environmentally friendly protein source, offering a pathway toward a more sustainable future.

Spirulina-An Invaluable Source of Macro- and Micronutrients with Broad Biological Activity and Application Potential

With population growth expected in the near future and the planet's limited resources, alternative food sources are already being looked for. In this context, spirulina is called the food of the future due to its rich nutritional composition. This blue-green alga is primarily a valuable source of protein (55-70%) containing all essential amino acids. In its composition, it also contains unsaturated fatty acids, minerals, vitamins, and pigments, including the valuable protein-pigment complex-phycocyanin. Due to its high content of complete protein and minerals such as iron and calcium, it is an excellent addition to diets, especially those of vegans and vegetarians. Despite several limitations to the use of spirulina, including its distinctive marine flavour, low consumer awareness, or relatively high price, scientists are attempting to enrich many food products with the microalga. This is supported not only by the improved nutritional composition of the fortified product but also by spirulina's impact on sustainable food production. Therefore, this review aims to create consumer attention by presenting spirulina as a valuable and sustainable food source with health-promoting potential and great future significance.

A novel co-metabolic mode with Spirulina powder in enhancing the anaerobic degradation of typical nitrogen heterocyclic compounds

Spirulina powder emerged as a novel and suitable co-metabolism substance significantly enhancing the anaerobic degradation of specific nitrogen heterocyclic compounds. On the addition of 1.0 mg/L of Spirulina powder, the reactor demonstrated optimal degradation efficiency for quinoline and indole, achieving ratios of 99.77 ± 1.83% and 99.57 ± 1.98%, respectively. Moreover, the incorporation of Spirulina powder resulted in increased concentrations of mixed liquor suspended solids, mixed liquor volatile suspended solids, proteins, and polysaccharides in anaerobic sludge. In addition, Spirulina powder led to reduced levels of Acinetobacter and enriched Aminicenantes genera incertae sedis, Levilinea, and Longilinea. The analysis of the archaeal community structure confirmed that the addition of Spirulina powder increased archaeal sequences, fostering greater richness and diversity in the archaeal community.

Comprehensive assessment of microalgal-based treatment processes for dairy wastewater

The dairy industry is becoming one of the biggest sectors within the global food industry, and these industries use almost 34% of the water. The amount of water used is governed by the production process and the technologies employed in the plants. Consequently, the dairy industries generate almost 0.2-10 L of wastewater per liter of processed milk, which must be treated before being discharged into water bodies. The cultivation of microalgae in a mixotrophic regime using dairy wastewater enhances biomass growth, productivity, and the accumulation of value-added product. The generated biomass can be converted into biofuels, thus limiting the dependence on petroleum-based crude oil. To fulfill the algal biorefinery model, it is important to utilize every waste stream in a cascade loop. Additionally, the harvested water generated from algal biomass production can be recycled for further microalgal growth. Economic and sustainable wastewater management, along with proper reclamation of nutrients from dairy wastewater, is a promising approach to mitigate the problem of water scarcity. A bibliometric study revealing limited work on dairy wastewater treatment using microalgae for biofuel production. And, limited work is reported on the pretreatment of dairy wastewater via physicochemical methods before microalgal-based treatment. There are still significant gaps remains in large-scale cultivation processes. It is also crucial to discover robust strains that are highly compatible with the specific concentration of contaminants, as this will lead to increased yields and productivity for the targeted bio-product. Finally, research on reutilization of culture media in photobioreactor is necessary to augument the productivity of the entire process. Therefore, the incorporation of the microalgal biorefinery with the wastewater treatment concept has great potential for promoting ecological sustainability.

Trends in extracting protein from microalgae Spirulina platensis, using innovative extraction techniques: mechanisms, potentials, and limitations

Microalgal, species are recognized for their high protein content, positioning them as a promising source of this macronutrient. Spirulina platensis, in particular, is noteworthy for its rich protein levels (70 g/100 g dw), which are higher than those of meat and legumes. Incorporating this microalgae into food can provide various benefits to human health due to its diverse chemical composition, encompassing high amount of protein and elevated levels of minerals, phenolics, essential fatty acids, and pigments. Conventional techniques employed for protein extraction from S. platensis have several drawbacks, prompting the exploration of innovative extraction techniques (IETs) to overcome these limitations. Recent advancements in extraction methods include ultrasound-assisted extraction, microwave-assisted extraction, high-pressure-assisted extraction, supercritical fluid extraction, pulse-electric field assisted extraction, ionic liquids assisted extraction, and pressurized liquid extraction. These IETs have demonstrated efficiency in enhancing protein yield of high quality while maximizing biomass utilization. This comprehensive review delves into the mechanisms, applications, and drawbacks associated with implementing IETs in protein extraction from S. platensis. Notably, these innovative methods offer advantages such as increased extractability, minimized protein denaturation, reduced solvent consumption, and lower energy consumption. However, safety considerations and the synergistic effects of combined extraction methods warrant further exploration and investigation of their underlying mechanisms.

Cradle-to-gate life cycle assessment of Spirulina bioplastic produced via plasticization with glycerol

Bioplastics have been used as alternatives to conventional petroleum-based plastics to lessen the burdens on marine and terrestrial environments due to their non-biodegradability and toxicity. However, recent studies have shown that not all bioplastics may be environmentally friendly. Microalgae, such as Spirulina that do not require arable land, have been identified as a potential bioplastic source. In this study, cradle-to-gate life cycle assessment (LCA) was carried out in openLCA program using the Agribalyse database, to evaluate the environmental impacts of Spirulina bioplastic, formed from plasticization of Spirulina powder with glycerol. Two processes were created for the inventories of (i) Spirulina powder and (ii) Spirulina bioplastic, where the output of the former served as an input for the latter. The extruded bioplastic sheets were food-grade and could be used as edible packaging materials. The bioplastic was also compared to conventional plastics and it was found that the energy consumption was 3.83 ± 0.26 MJ/kg-bioplastic, which was 12% and 22% higher than that of LDPE and PVC plastic films, respectively. The impacts on the environment showed that the chemical growth medium (Zarrouk medium) and electricity were the main contributors in most of the categories. Compared to the PVC and LDPE films, the Spirulina bioplastic's impacts on the aquatic ecosystems were 2-3 times higher. The global warming potential of the Spirulina bioplastic was 1.99 ± 0.014 kg CO2 eq, which was 23% and 47% lower than that of LDPE and PVC films, respectively. Sensitivity analysis was carried out by changing the electricity source and using alternative growth media. Except for the case of switching to solar energy, the results for other cases did not differ significantly from the base case scenario. Future studies were suggested to identify different greener alternatives to the growth medium as well as different energy mixes for more environmentally benign solutions.

Purification of thioredoxin reductase from Spirulina platensis by affinity chromatography and investigation of kinetic properties

The thioredoxin system consists of thioredoxin (Trx), thioredoxin reductase (TrxR) and nicotinamide adenine dinucleotide phosphate (NADPH). Spirulina platensis, which is one of the blue-green algae in the form of spiral rings, belongs to the cyanobacteria class. Spirulina platensis can produce Trx under stress conditions. If it can produce Trx, it also has TrxR activity. Therefore, in this study, the TrxR enzyme was purified for the first time from Spirulina platensis, an algae the most grown and also used as a nutritional supplement in the world. A two-step purification process was used: preparation of the homogenate and 2',5'-ADP sepharose 4B affinity chromatography. The enzyme was purified with a purification fold of 1059.51, a recovery yield of 9.7 %, and a specific activity of 5.77 U/mg protein. The purified TrxR was tested for purity by SDS-PAGE. The molecular weight of its subunit was found to be about 45 kDa. Optimum pH, temperature and ionic strength of the enzyme were pH 7.0, 40 °C and 750 mM in phosphate buffer respectively. The Michaelis constant (Km) and maximum velocity of enzyme (Vmax) values for NADPH and 5,5'-dithiobis (2-nitrobenzoic acid) (DTNB) are 5 μM and 2.2 mM, and 0.0033 U/mL and 0.0044 U/mL, respectively. Storage stability of the purified enzyme was determined at several temperatures. The inhibition effects of Ag+, Cu2+, Al3+ and Se4+ metal ions on the purified TrxR activity were investigated in vitro. While Se4+ ion increased the enzyme activity, other tested metal ions showed different type of inhibitory effects on the Lineweaver-Burk graphs.

Photobioreactor configurations in cultivating microalgae biomass for biorefinery

Microalgae, highly prized for their protein, lipid, carbohydrate, phycocyanin, and carotenoid-rich biomass, have garnered significant industrial attention in the context of third-generation (3G) biorefineries, seeking sustainable alternatives to non-renewable resources. Two primarily cultivation methods, open ponds and closed photobioreactors systems, have emerged. Open ponds, favored for their cost-effectiveness in large-scale industrial production, although lacking precise environmental control, contrast with closed photobioreactors, offering controlled conditions and enhanced biomass production at the laboratory scale. However, their high operational costs challenge large-scale deployment. This review comprehensively examines the strength, weakness, and typical designs of both outdoor and indoor microalgae cultivation systems, with an emphasis on their application in terms of biorefinery concept. Additionally, it incorporates techno-economic analyses, providing insights into the financial aspects of microalgae biomass production. These multifaceted insights, encompassing both technological and economic dimensions, are important as the global interest in harnessing microalgae's valuable resources continue to grow.

Synergic association of the consortium Arthrospira maxima with the microalga growth-promoting bacterium Azospirillum cultured under the stressful biogas composition

The present study evaluates the association of the blue-green microalga Arthrospira maxima (Spirulina), which is known for its CO2 fixation, biomass, and high-value metabolite production, with the microalga growth-promoting bacterium Azospirillum brasilense under the stressful composition of biogas. The results demonstrated that A. maxima co-cultured with A. brasilense under the high CO2 (25%) and methane (CH4; 75%) concentrations of biogas recorded a CO2 fixation rate of 0.24 ± 0.03 g L-1 days-1, thereby attaining a biomass production of 1.8 ± 0.03 g L-1. Similarly, the biochemical composition quality of this microalga enhanced the attainment of higher contents of carbohydrates, proteins, and phycocyanin than cultured alone. However, metabolites other than tryptophan (Trp) and indole-3-acetic acid could have supported this beneficial interaction. Overall, the results demonstrate that this prokaryotic consortium of A. maxima-A. brasilense established a synergic association under biogas, which represents a sustainable strategy to improve the bio-refinery capacity of this microalga and increase the usefulness of A. brasilense in multiple economic sectors.

The Effects of Spirulina Supplementation on Cardiometabolic Risk Factors: A Narrative Review

Spirulina (Arthrospira platensis) is a cyanobacterium associated with multiple health benefits. Cardiometabolic diseases such as cardiovascular disease, nonalcoholic fatty liver disease, and diabetes are prevalent yet usually preventable non-communicable diseases. Modifiable risk factors for cardiometabolic diseases include excessive body weight, body inflammation, atherogenic lipid profile, and imbalanced glucose metabolism. This review explores the effects of spirulina on cardiometabolic diseases risk factors. Spirulina was effective in reducing body weight, body mass index, and waist circumference, with a potential dose-dependent effect. It also decreased interleukin 6, an important biomarker of body inflammation, by inhibiting NADPH oxidase enzyme, and lowering insulin resistance. spirulina supplementation also reduced triglycerides, low-density lipoprotein cholesterol, and increased high-density lipoprotein cholesterol. Additionally, spirulina reduced fasting blood sugar and post-prandial blood sugar and increased insulin sensitivity, but no effect was observed on glycated hemoglobin A1c. The diverse nutrients, such as phycocyanin, gamma-linolenic acid, and vitamin B12, present in spirulina contribute to its cardiometabolic benefits. The doses used are heterogeneous for most studies, ranging from 1 to 8 grams daily, but most studies administered spirulina for 3 months to observe an effect. The collective evidence suggests that spirulina supplements may help improve risk factors for cardiometabolic diseases, thus, preventing its development. However, due to the heterogeneity of the results, more randomized clinical trials are needed to draw robust conclusions about spirulina's therapeutic potential in ameliorating risk factors for cardiometabolic diseases and fully elucidate the mechanisms by which it exerts its effects.

Effect of seawater on the biomass composition of Spirulina produced at a pilot-scale

The microalga Arthrospira platensis BEA 005B was produced in 11.4 m3 raceway photobioreactors and a culture medium based on commercial fertilisers and either freshwater or seawater. The biomass productivity of the reactors operated at a fixed dilution rate of 0.3 day-1 decreased from 22.9 g·m-2·day-1 when operated using freshwater to 16.3 g·m-2·day-1 when the biomass was produced using seawater. The protein content of the biomass produced in seawater was lower; however, the content of essential amino acids including valine, leucine and isoleucine was higher. Seawater also triggered the production of carotenoids and altered the synthesis and accumulation of fatty acids. For example, the biomass produced using seawater showed a 319% and 210% higher content of oleic and eicosenoic acid, respectively. The results demonstrate that it is possible to produce the selected microalga using seawater after an adaptation period and that the composition of the produced biomass is suitable for food applications.

A precise microalgae farming for CO2 sequestration: A critical review and perspectives

Microalgae are great candidates for CO2 sequestration and sustainable production of food, feed, fuels and biochemicals. Light intensity, temperature, carbon supply, and cell physiological state are key factors of photosynthesis, and efficient phototrophic production of microalgal biomass occurs only when all these factors are in their optimal range simultaneously. However, this synergistic state is often not achievable due to the ever-changing environmental factors such as sunlight and temperature, which results in serious waste of sunlight energy and other resources, ultimately leading to high production costs. Most control strategies developed thus far in the bioengineering field actually aim to improve heterotrophic processes, but phototrophic processes face a completely different problem. Hence, an alternative control strategy needs to be developed, and precise microalgal cultivation is a promising strategy in which the production resources are precisely supplied according to the dynamic changes in key factors such as sunlight and temperature. In this work, the development and recent progress of precise microalgal phototrophic cultivation are reviewed. The key environmental and cultivation factors and their dynamic effects on microalgal cultivation are analyzed, including microalgal growth, cultivation costs and energy inputs. Future research for the development of more precise microalgae farming is discussed. This study provides new insight into developing cost-effective and efficient microalgae farming for CO2 sequestration.

Optimal Laboratory Cultivation Conditions of Limnospira maxima for Large-Scale Production

Cultivating Limnospira maxima, renowned for its abundant proteins and valuable pigments, faces substantial challenges rooted in the limited understanding of its optimal growth parameters, associated high costs, and constraints in the procurement of traditional nitrogen sources, particularly NaNO3. To overcome these challenges, we conducted a comprehensive 4 × 3 factorial design study. Factors considered included white, red, blue, and yellow light spectra, along with nitrogen sources NaNO3 and KNO3, as well as a nitrogen-free control, for large-scale implementation. Optimal growth, measured by Optical Density, occurred with white and yellow light combined with KNO3 as the nitrogen source. These conditions also increased dry weight and Chl-a content. Cultures with nitrogen deprivation exhibited high values for these variables, attributed to carbon accumulation in response to nitrogen scarcity. Phycocyanin, a crucial pigment for nutrition and industry, reached its highest levels in cultures exposed to white light and supplemented with KNO3, with an impressive content of 384.11 g kg-1 of dry weight. These results highlight the efficacy and cost-efficiency of using a combination of white light and KNO3 for large-scale L. maxima cultivation. This strategy offers promising opportunities to address global food security challenges and enhance the production of industrially relevant pigments.

Real-Time Sensor Data Profile-Based Deep Learning Method Applied to Open Raceway Pond Microalgal Productivity Prediction

Microalgal biotechnology holds the potential for renewable biofuels, bioproducts, and carbon capture applications due to unparalleled photosynthetic efficiency and diversity. Outdoor open raceway pond (ORP) cultivation enables utilization of sunlight and atmospheric carbon dioxide to drive microalgal biomass synthesis for production of bioproducts including biofuels; however, environmental conditions are highly dynamic and fluctuate both diurnally and seasonally, making ORP productivity prediction challenging without time-intensive physical measurements and location-specific calibrations. Here, for the first time, we present an image-based deep learning method for the prediction of ORP productivity. Our method is based on parameter profile plot images of sensor parameters, including pH, dissolved oxygen, temperature, photosynthetically active radiation, and total dissolved solids. These parameters can be remotely monitored without physical interaction with ORPs. We apply the model to data we generated during the Unified Field Studies of the Algae Testbed Public-Private-Partnership (ATP3 UFS), the largest publicly available ORP data set to date, which includes millions of sensor records and 598 productivities from 32 ORPs operated in 5 states in the United States. We demonstrate that this approach significantly outperforms an average value based traditional machine learning method (R2 = 0.77 ≫ R2 = 0.39) without considering bioprocess parameters (e.g., biomass density, hydraulic retention time, and nutrient concentrations). We then evaluate the sensitivity of image and monitoring data resolutions and input parameter variations. Our results demonstrate ORP productivity can be effectively predicted from remote monitoring data, providing an inexpensive tool for microalgal production and operational forecasting.

Influence of cold atmospheric pressure plasma treatment of Spirulina platensis slurry over biomass characteristics

Cold atmospheric pressure plasma (CAPP) technique is an innovative non-thermal approach for food preservation and decontamination. This study aimed to evaluate the effect of CAPP power density on microorganism inactivation and quality of Spirulina platensis (S. platensis) slurry. 91.31 ± 1.61% of microorganism were inactivated within 2.02 ± 0.11 min by 26.67 W/g CAPP treatment under 50 ℃. Total phenolic, Chlorophyll-a (Chl-a), and carotenoids contents were increased by 20.51%, 63.55%, and 70.04% after 20.00 W/g CAPP treatment. Phycobiliproteins (PBPs), protein, intracellular polysaccharide, and moisture content of S. platensis was decreased, while vividness, lightness, color of yellow and green, antioxidant activity, Essential Amino Acid Index were enhanced after CAPP treatment. The nutrient release and filaments breakage of CAPP-treated S. platensis improved its bio-accessibility. The findings provided a deep understanding and insight into the influence of CAPP treatment on S. platensis, which were meaningful for optimizing its sterilization and drying processing condition.

The Experimental Development of Emulsions Enriched and Stabilized by Recovering Matter from Spirulina Biomass: Valorization of Residue into a Sustainable Protein Source

Spirulina consists of a cluster of green-colored cyanobacteria; it is commonly consumed as a food or food supplement rich in bioactive compounds with antioxidant activity, predominantly C-phycocyanin (C-PC), which is related to anti-inflammatory action and anticancer potential when consumed frequently. After C-PC extraction, the Spirulina residual biomass (RB) is rich in proteins and fatty acids with the potential for developing food products, which is interesting from the circular economy perspective. The present work aimed to develop a vegan oil-in-water emulsion containing different contents of Spirulina RB, obtaining a product aligned with current food trends. Emulsions with 3.0% (w/w) of proteins were prepared with different chickpea and Spirulina RB ratios. Emulsifying properties were evaluated regarding texture and rheological properties, color, antioxidant activity, and droplet size distribution. The results showed that it was possible to formulate stable protein-rich emulsions using recovering matter rich in protein from Spirulina as an innovative food ingredient. All the concentrations used of the RB promoted the formulation of emulsions presenting interesting rheological parameters compared with a more traditional protein source such as chickpea. The emulsions were also a source of antioxidant compounds and maintained the color for at least 30 days after production.

Techno-economic assessment of co-production of edible bioplastic and food supplements from Spirulina

Large amount of plastic wastes harming the environment have raised concerns worldwide on finding alternatives to non-biodegradable plastics. Microalgae has been found as a potential source for bioplastic production, besides its more common application in the pharmaceutical and nutraceutical industry. In this study, the objective was to techno-economically evaluate the large-scale co-production of Spirulina powder as food supplements and edible bioplastic for food packaging. The scale of production was large enough to satisfy 1% of local (Thailand) plastic demand (i.e., approx. 1200 MT y-1), and 1% of the global Spirulina demand (approx. 1000 MT y-1) as food supplements. Results showed that the co-production of the Spirulina powder and bioplastic revealed an attractive venture with a payback time (PBT) as low as 2.6 y and ROI as high as 38.5%. This was because the revenues generated were as high as US$ 55.6 million y-1, despite high capital (US$ 55.7 million) and operating (US$ 34.9 million y-1) costs. Sensitivity analysis showed differences in the profitability based on variations of major parameters in the study, where the split ratio of biomass used for food supplement versus bioplastic production and the bioplastic's selling price were found to be the most sensitive.

Integrated culture and harvest systems for improved microalgal biomass production and wastewater treatment

Microalgae cultivation in wastewater has received much attention as an environmentally sustainable approach. However, commercial application of this technique is challenging due to the low biomass output and high harvesting costs. Recently, integrated culture and harvest systems including microalgae biofilm, membrane photobioreactor, microalgae-fungi co-culture, microalgae-activated sludge co-culture, and microalgae auto-flocculation have been explored for efficiently coupling microalgal biomass production with wastewater purification. In such systems, the cultivation of microalgae and the separation of algal cells from wastewater are performed in the same reactor, enabling microalgae grown in the cultivation system to reach higher concentration, thus greatly improving the efficiency of biomass production and wastewater purification. Additionally, the design of such innovative systems also allows for microalgae cells to be harvested more efficiently. This review summarizes the mechanisms, characteristics, applications, and development trends of the various integrated systems and discusses their potential for broad applications, which worth further research.

Roles of microalgae-based biofertilizer in sustainability of green agriculture and food-water-energy security nexus

For years, agrochemical fertilizers have been used in agriculture for crop production. However, intensive utilization of chemical fertilizers is not an ecological and environmental choice since they are destroying soil health and causing an emerging threat to agricultural production on a global scale. Under the circumstances of the increasing utilization of chemical fertilizers, cultivating microalgae to produce biofertilizers would be a wise solution since desired environmental targets will be obtained including (1) replacing chemical fertilizer while improving crop yields and soil health; (2) reducing the harvest of non-renewable elements from limited natural resources for chemical fertilizers production, and (3) mitigating negative influences of climate change through CO₂ capture through microalgae cultivation. Recent improvements in microalgae-derived-biofertilizer-applied agriculture will be summarized in this review article. At last, the recent challenges of applying biofertilizers will be discussed as well as the perspective regarding the concept of circular bio-economy and sustainable development goals (SDGs).

Exploring the Benefits of Phycocyanin: From Spirulina Cultivation to Its Widespread Applications

Large-scale production of microalgae and their bioactive compounds has steadily increased in response to global demand for natural compounds. Spirulina, in particular, has been used due to its high nutritional value, especially its high protein content. Promising biological functions have been associated with Spirulina extracts, mainly related to its high value added blue pigment, phycocyanin. Phycocyanin is used in several industries such as food, cosmetics, and pharmaceuticals, which increases its market value. Due to the worldwide interest and the need to replace synthetic compounds with natural ones, efforts have been made to optimize large-scale production processes and maintain phycocyanin stability, which is a highly unstable protein. The aim of this review is to update the scientific knowledge on phycocyanin applications and to describe the reported production, extraction, and purification methods, including the main physical and chemical parameters that may affect the purity, recovery, and stability of phycocyanin. By implementing different techniques such as complete cell disruption, extraction at temperatures below 45 °C and a pH of 5.5-6.0, purification through ammonium sulfate, and filtration and chromatography, both the purity and stability of phycocyanin have been significantly improved. Moreover, the use of saccharides, crosslinkers, or natural polymers as preservatives has contributed to the increased market value of phycocyanin.

Effect of Spirulina Dietary Supplementation in Modifying the Rumen Microbiota of Ewes

Supplementing ruminant diets with microalgae, may prove an effective nutritional strategy to manipulate rumen microbiota. Forty-eight ewes were divided into four homogenous groups (n = 12) according to their fat-corrected milk yield (6%), body weight, age, and days in milk, and were fed individually with concentrate, alfalfa hay, and wheat straw. The concentrate of the control group (CON) had no Spirulina supplementation, while in the treated groups 5 (SP5), 10 (SP10), and 15 g (SP15) of Spirulina were supplemented as an additive in the concentrate. An initial screening using metagenomic next-generation sequencing technology was followed by RT-qPCR analysis for the targeting of specific microbes, which unveiled the main alterations of the rumen microbiota under the Spirulina supplementation levels. The relative abundance of Eubacterium ruminantium and Fibrobacter succinogenes in rumen fluid, as well as Ruminococcus albus in rumen solid fraction, were significantly increased in the SP15 group. Furthermore, the relative abundance of Prevotella brevis was significantly increased in the rumen fluid of the SP5 and SP10 groups. In contrast, the relative abundance of Ruminobacter amylophilus was significantly decreased in the rumen fluid of the SP10 compared to the CON group, while in the solid fraction it was significantly decreased in the SP groups. Moreover, the relative abundance of Selenomonas ruminantium was significantly decreased in the SP5 and SP15 groups, while the relative abundance of Streptococcus bovis was significantly decreased in the SP groups. Consequently, supplementing 15 g Spirulina/ewe/day increased the relative abundance of key cellulolytic species in the rumen, while amylolytic species were reduced only in the solid fraction.

Bio-Converted Spirulina for Nutraceutical Chewing Candy Formulations Rich in L-Glutamic and Gamma-Aminobutyric Acids

This study aimed at evaluating changes of microalgae Spirulina during its fermentation with Lactiplantibacillus plantarum No. 122 strain, and further at incorporating Spirulina bio-converted for nutraceuticals rich in L-glutamic (L-Glu) and gamma-aminobutyric acids (GABA) into sucrose-free chewing candy (gummy) preparations. Fermented Spirulina had higher b* (yellowness) coordinates than untreated (non-fermented), and fermentation duration (24 and 48 h) had a statistically significant effect on colour coordinates. The highest contents of L-glutamic and gamma-aminobutyric acids (4062 and 228.6 mg/kg, respectively) were found in 24 and 48 h-fermented Spirulina, respectively. Fermentation increased the content of saturated fatty acids and omega-3 in Spirulina, while monounsaturated fatty acids and omega-6 were reduced. The addition of fermented Spirulina (FSp) significantly affected hardness, decreased lightness and yellowness, and increased the greenness of chewing candies. All chewing candy samples (with xylitol) prepared with 3 and 5 g of FSp and 0.2 µL of Citrus paradise essential oil received the highest scores for overall acceptability, and the highest intensity (0.052) of emotion "happy" was elicited by the sample group containing xylitol, agar, ascorbic acid, 3 g of FSp, and 0.1 µL of Mentha spicata essential oil. As an outcome of this research, one may conclude that fermented Spirulina has significant potential as an innovative ingredient in the production of healthier sucrose-free nutraceutical chewing candies.

Submerged and Solid-State Fermentation of Spirulina with Lactic Acid Bacteria Strains: Antimicrobial Properties and the Formation of Bioactive Compounds of Protein Origin

The aim of this study was to investigate the changes in bioactive compounds (L-glutamic acid (L-Glu), gamma-aminobutyric acid (GABA) and biogenic amines (BAs)) during the submerged (SMF) and solid-state (SSF) fermentation of Spirulina with lactobacilli strains (Lacticaseibacillus paracasei No. 244; Levilactobacillus brevis No. 173; Leuconostoc mesenteroides No. 225; Liquorilactobacillus uvarum No. 245). The antimicrobial properties of the untreated and fermented Spirulina against a variety of pathogenic and opportunistic strains were tested. The highest concentrations of L-Glu (3841 mg/kg) and GABA (2396 mg/kg) were found after 48 h of SSF with No. 173 and No. 244 strains, respectively. The LAB strain used for biotreatment and the process conditions, as well as the interaction of these factors, had statistically significant effects on the GABA concentration in Spirulina (p ≤ 0.001, p = 0.019 and p = 0.011, respectively). In all cases, the SSF of Spirulina had a higher total BA content than SMF. Most of the fermented Spirulina showed exceptional antimicrobial activity against Staphylococcus aureus but not against the other pathogenic bacteria. The ratios of BA/GABA and BA/L-Glu ranged from 0.5 to 62 and from 0.31 to 10.7, respectively. The GABA content was correlated with putrescine, cadaverine, histamine, tyramine, spermidine and spermine contents. The L-glutamic acid concentration showed positive moderate correlations with tryptamine, putrescine, spermidine and spermine. To summarize, while high concentrations of desirable compounds are formed during fermentation, the formation of non-desirable compounds (BAs) must also be considered due to the similar mechanism of their synthesis as well as the possibility of obtaining high concentrations in the end products.

C-phycocyanin production with high antioxidant activity of a new thermotolerant freshwater Desertifilum tharense UAM-C/S02 strain

A native cyanobacterial strain, Desertifilum tharense UAM-C/S02, was studied as a possible C-phycocyanin (C-PC) producer. Photosynthetic activity (PA) assays through oxygen production determined the proper temperature and range of irradiances to be tested in a stirred tank photobioreactor. The highest C-PC productivity (97 mg L^-1 d^-1), with a yield of 86.46 mg_C-PC g_B^-1 was obtained at 730 µmol photons m^-2 s^-1 with a biomass productivity of 608 mg L^-1 d^-1 and the CO₂ fixation rate was 1,194  mg L^-1 d^-1. The 1.81 crude extract purity value is the highest reported for this genus, which was improved to biomarker-grade purity after a two-step purification strategy comprising precipitation with ammonium sulfate, followed by dialysis. The purified C-PC was almost entirely radical-free using 1 mg mL^-1, which validates its potential use in therapeutic formulations.

Microalgal bioactive metabolites as promising implements in nutraceuticals and pharmaceuticals: inspiring therapy for health benefits

The rapid increase in global population and shrinkage of agricultural land necessitates the use of cost-effective renewable sources as alternative to excessive resource-demanding agricultural crops. Microalgae seem to be a potential substitute as it rapidly produces large biomass that can serve as a good source of various functional ingredients that are not produced/synthesized inside the human body and high-value nonessential bioactive compounds. Microalgae-derived bioactive metabolites possess various bioactivities including antioxidant, anti-inflammatory, antimicrobial, anti-carcinogenic, anti-hypertensive, anti-lipidemic, and anti-diabetic activities, thereof rapidly elevating their demand as interesting option in pharmaceuticals, nutraceuticals and functional foods industries for developing new products. However, their utilization in these sectors has been limited. This demands more research to explore the functionality of microalgae derived functional ingredients. Therefore, in this review, we intended to furnish up-to-date knowledge on prospects of bioactive metabolites from microalgae, their bioactivities related to health, the process of microalgae cultivation and harvesting, extraction and purification of bioactive metabolites, role as dietary supplements or functional food, their commercial applications in nutritional and pharmaceutical industries and the challenges in this area of research.

Graphical abstract

Enhancement of Cell Behavior by the Polysaccharide Extract of Arthrospira and Potential Biomedical Applications

Arthrospira is one of the most studied cyanobacteria and has been reported with practical applications. Among the substances derived from Arthrospira, polysaccharides have received relatively less attention than phycocyanins, though they have more abundant structural variations and specific properties. Herein, a new Arthrospira-derived sulfated polysaccharide was explored for its potential bioactive functions. The ability of this sulfated polysaccharide to promote the behavior of neural stem cells (NSCs) in three-dimensional hydrogel was examined for the first time. NSCs encapsulated in the sulfated polysaccharide-containing hydrogel showed better proliferation than the control hydrogel as well as a unique cell clustering behavior, i.e., formation of multicellular spherical clusters (40-60 μm). The sulfated polysaccharide, in an appropriate range of concentration (5 mg/mL), also maintained the stemness of NSCs in hydrogel and facilitated their differentiation. In addition, the potentials of the new sulfated polysaccharide as a coating material and as a component for drug carrier were verified. The sulfated polysaccharide-modified substrate exhibited superhydrophilicity (contact angle ~9°) and promoted cell adhesion to the substrate. Composite nanoparticles composed of the sulfated polysaccharide and other differently charged polysaccharides were produced with an average diameter of ~240 nm and estimated drug loading of ~18%. The new Arthrospira-derived sulfated polysaccharide is a promising candidate for cell culture, surface-modification, and drug-delivery applications in the biomedical field.

A smart and precise mixing strategy for efficient and cost-effective microalgae production in open ponds

Microalgae biotechnology is a great candidate for carbon neutralization, wastewater treatment and the sustainable production of biofuels and food. Efficient and cost-effective microalgae production depends on highly coordinating the resources used for algal growth. However, dynamic natural disturbances such as culture temperature and sunlight can lead to the poor coordination and waste of resources. Open ponds are the most commonly used commercial microalgal production systems, and enhanced mixing can significantly increase their productivity, but mixing energy can be seriously wasted due to dynamic disturbances, presenting a hindrance to further reducing production costs. Herein, a smart and precise mixing strategy was developed for open ponds in which a paddle wheel's stirring speed for an open pond was smartly and precisely controlled in real time based on dynamic variations in light intensity and culture temperature. The proposed technology achieved the same biomass productivity of Spirulina platensis (8.37 g m^-2 day^-1) as a control with a constant high mixing rate under dynamic disturbances while reducing mixing energy inputs by approximately 30 % compared to the control. This study provides a promising method to address serious resource waste and poor coordination due to dynamic natural disturbances, holding great potential for efficient and cost-effective microalgae production.

Effect of Electrofiltration on the Dewatering Kinetics of Arthrospira platensis and Biocompound Recovery

Arthrospira platensis (A. platensis) is a microalga with a wide range of commercial uses. One of the main concerns that needs to be addressed in microalgae biorefineries is the costs associated with the harvesting and concentration steps. Filtration has been shown to be an effective technique for concentrating microalgae and recent studies have attempted to enhance membrane filtration by applying an external electric field to the filtration cell. This study consisted of assessing the use of electrically assisted filtration (electrofiltration) at 60 A/m2 and 1 bar for the dewatering of A. platensis, as well as the effect of pretreating the microalgae with ultrasounds (US) on the filtration process. Untreated A. platensis exhibited better filtration kinetics than US-treated A. platensis, and electrofiltration was found to increase the cake dryness. More protein and pigments were present in the US-treated microalgae solution compared to the untreated microalgae, which led to the presence of higher concentrations of protein and pigments in the filtrate streams after pressure filtration at 1 bar without the application of an external electric field. Electrofiltration was found to consume less energy compared to traditional drying techniques used for A. platensis. However, electrofiltration degrades the biocompounds present in the filtrate and cake due to pH changes and other electrophoresis phenomena, which shows the need to optimize the process in future work.

Photobioreactors for cultivation and synthesis: Specifications, challenges, and perspectives

Due to their versatility and the high biomass yield produced, cultivation of phototrophic organisms is an increasingly important field. In general, open ponds are chosen to do it because of economic reasons; however, this strategy has several drawbacks such as poor control of culture conditions and a considerable risk of contamination. On the other hand, photobioreactors are an attractive choice to perform cultivation of phototrophic organisms, many times in a large scale and an efficient way. Furthermore, photobioreactors are being increasingly used in bioprocesses to obtain valuable chemical products. In this review, we briefly describe different photobioreactor set-ups, including some of the recent designs, and their characteristics. Additionally, we discuss the current challenges and advantages that each different type of photobioreactor presents, their applicability in biocatalysis and some modern modeling tools that can be applied to further enhance a certain process.

Cost Reduction in the Production of Spirulina Biomass and Biomolecules from Indole-3-Acetic Acid Supplementation in Different Growth Phases

Despite the great potential for the industrial application of microalgae, production costs are still too high to make them a competitive raw material for commodities. Therefore, studying more efficient cultivation strategies in biomass production and economic viability is necessary. In this sense, this work aimed to reduce the production costs of biomass and biomolecules using phytohormone indole-3-acetic acid in different phases of Spirulina sp. LEB 18 cultivation. The experiments were conducted on bench scale indoor for 30 days. In each couple of experiments, the phytohormone was added on different days. The supplementation of indole-3-acetic acid on half of the growth deceleration phase of the microalga showed a cost reduction of 27%, 34%, and 75% for biomass, proteins, and carbohydrates, respectively. In addition, the strategy increased the final biomass concentration and carbohydrate content at 31.2 and 33.8%, respectively, compared to the condition without phytohormone. This study is the starting point for implementing phytohormone supplementation in industrial microalgal cultures.

Current perspectives, future challenges and key technologies of biohydrogen production for building a carbon-neutral future: A review

The ever-increasing quantity of greenhouse gases in the atmosphere can be attributed to the rapid increase in the world population as well as the expansion of globalization. Hence, achieving carbon neutrality by 2050 stands as a challenging task to accomplish. Global industrialization had necessitated the need to enhance the current production systems to reduce greenhouse gases emission, whilst promoting the capture of carbon dioxide from atmosphere. Hydrogen is often touted as the fuel of future via substituting fossil-based fuels. In this regard, renewable hydrogen happens to be a niche sector of novel technologies in achieving carbon neutrality. Microalgae-based biohydrogen technologies could be a sustainable and economical approach to produce hydrogen from a renewable source, while simultaneously promoting the absorption of carbon dioxide. This review highlights the current perspectives of biohydrogen production as an alternate source of energy. In addition, future challenges associated with biohydrogen production at large-scale application, storage and transportation are included. Key technologies in producing biohydrogen are finally described in building a carbon-neutral future.

Monitoring effect of nickel, copper, and zinc on growth and photosynthetic pigments of Spirulina platensis with suitability investigation in Idku Lake

Owing to the increase of pollutant sources in oceans, seas, and lakes, there is an expected effect on growth and metabolism of planktonic algae which are considered primary producers in the ecosystem. Therefore, it becomes urgent to carry out laboratory studies to test to what extent these pollutants can affect the growth of algae which is necessary as a food for marine fishes. Spirulina is considered the most important algal species due to its high nutritional value for humans and animals. Therefore, this work investigated the effect of different concentrations of Ni²⁺, Zn²⁺, and Cu²⁺ metal ion pollutants on growth of the blue-green alga Spirulina platensis. EC50 was identified to be around 2 mg/l for the three heavy metals. The suitability of Idku Lake for Spirulina platensis growth was investigated using multi-criteria spatial modeling integrated with remotely sensed data processing. Spatial distribution maps of turbidity, water nutrients, and phytoplankton were the input criteria used to assess Idku Lake's suitability. The results obtained proved that low concentrations of the tested heavy metals stimulated growth and pigment fractions (chlorophyll a, carotenoids, and total phycobilins content) but to different degrees. The inhibitory effect was more prominent in the case of copper ions than zinc and nickel ions with all concentrations used. The overall suitability map of Spirulina platensis in Idku Lake showed that the whole lake is suitable for growth and proliferation except for the northwestern corner due to the high salinity levels. The present paper helps to understand the behavior of algae responding to environmental pollution, which supports environmental planners with the necessary baseline for investigating the fate of pollutants and the potential risk.

Effect of Dietary Blue-Green Microalgae Inclusion as a Replacement to Soybean Meal on Laying Hens' Performance, Egg Quality, Plasma Metabolites, and Hematology

Spirulina platensisis (SP) is a blue-green microalgae with a high value for animal and poultry nutrition. The study employed 250 40-week-old, HY-Line W-36 commercial laying hens. The layers received one of five experimental diet substitutes in five groups for 10 consecutive weeks (five replicates of 10 hens each group); a soybean-corn basal diet formulation without SP (Control group) or the soybean partially substituted with 3% SP, 6% SP, 9% SP, and 12% SP (for the remaining four groups). The results showed that dietary SP treatment significantly (p < 0.05) improved the productive performance, egg quality, blood metabolites, and hematological parameters of laying hens. In addition, there were linear and quadratic effects for increasing the levels of SP inclusion into the layer diets; however, the highest values of most parameters were observed when using 9% SP (90 g/kg of the layer diets). Furthermore, the results showed that 4.7% of the soybean meal ingredient in the layer diet could be replaced by 1% of SP. In conclusion, the partial replacement of soybean meal by SP into layer diets could be used as a promising nutritional approach to optimize the performance of laying hens.

Alternative Solvents for the Biorefinery of Spirulina: Impact of Pretreatment on Free Fatty Acids with High Added Value

The growing demand for molecules of interest from microalgal biomass, such as phycobiliproteins, has led to an accumulation of unused by-products. For example, phycocyanin, obtained by the extraction of Spirulina, generated cakes rich in non-polar molecules of interest, such as free fatty acids (FFAs). These FFAs were generally considered as markers of lipidome degradation, but represented a relevant alternative to topical antibiotics, based on a biomimetic approach. In order to develop a sustainable Spirulina biorefinery scheme, different pretreatments and alternative solvents were screened to identify the best combination for the valorization of FFAs. Thus, five pre-treatments were studied including a phycocyanin extraction by-product. The following three biobased solvents were selected: ethyl acetate (EtOAc), dimethyl carbonate (DMC) and a fatty acid-based natural deep eutectic solvent (NaDES). The pigment and fatty acid profiles were established by spectroscopic and chromatographic approaches. NaDES demonstrated superior extraction capacity and selectivity compared to other biobased solvents, regardless of pretreatment. In contrast, EtOAc and DMC showed a greater diversity of FFAs, with a predominance of polyunsaturated fatty acids (PUFAs). The by-product has also been highlighted as a relevant raw material facilitating the recovery of FFAs. These results pave the way for a green biorefinery of the lipid fraction and phycobiliproteins of microalgae.

Influence of Geographical Location of Spirulina (Arthrospira platensis) on the Recovery of Bioactive Compounds Assisted by Pulsed Electric Fields

Spirulina (Arthrospira platensis) has been consumed by humans since ancient times. It is rich in high added-value compounds such as chlorophylls, carotenoids and polyphenols. Pulsed electric fields (PEF) is an innovative non-thermal technique that improves the extraction of bioactive compounds from diverse sources. PEF pre-treatment (3 kV/cm, 100 kJ/kg) combined with supplementary extraction with binary solvents at different times was evaluated to obtain the optimal conditions for extraction. In addition, the results obtained were compared with conventional treatment (without PEF pre-treatment and constant shaking) and different strains of Spirulina from diverse geographical locations. The optimal extraction conditions for recovering the bioactive compounds were obtained after applying PEF treatment combined with the binary mixture EtOH/H2O for 180 min. The recovery of total phenolic content (TPC) (19.76 ± 0.50 mg/g DM (dry matter) and carotenoids (0.50 ± 0.01 mg/g DM) was more efficient in the Spirulina from Spain. On the other hand, there was a higher recovery of chlorophylls in the Spirulina from China. The highest extraction of total antioxidant compounds was in Spirulina from Costa Rica. These results show that PEF, solvents and the condition of growing affect the extraction of antioxidant bioactive compounds from Spirulina. The combination of PEF and EtOH/H2O is a promising technology due to its environmental sustainability.

Factorial Optimization of Ultrasound-Assisted Extraction of Phycocyanin from Synechocystis salina: Towards a Biorefinery Approach

PC is a bioactive and colorant compound widely sought in the food, nutraceutical and cosmetic industries, and one of the most important pigments produced by Synechocystis salina. However, the general extraction process is usually time-consuming and expensive, with low extraction yields—thus compromising a feasible and sustainable bioprocess. Hence, new extraction technologies (e.g., ultrasound assisted-extraction or UAE) emerged in the latest years may serve as a key step to make the overall bioprocess more competitive. Therefore, this study aimed at optimizing the yields of phycocyanin (PC) rich-extracts of S. salina by resorting to UAE; in attempts to explore this process in a more economically feasible way; valorization of the remaining cyanobacterial biomass, via extraction of other bioactive pigments and antioxidants, was tackled within a biorefinery perspective. A two-stage extraction (using ethanol and water) was thus performed (because it favors PC extraction); other bioactive pigments, including chlorophyll a (chl a), carotenoids, and other phycobiliproteins (PBPs), but also antioxidant (AOX) capacity and extraction yields were also evaluated for their optimum UAE yields. A factorial design based on Box–Behnken model was developed; and the influence of such extraction parameters as biomass to solvent ratio (B/S ratio = 1.5–8.5 mg·mL⁻¹), duty cycle (DT = 40–100%), and percentage of amplitude (A = 40–100%) were evaluated. The model predicted higher PC yields with high B/S ratio = 6 mg·mL⁻¹, lower DT = 80% and an A = 100%. Classical extraction was compared with UAE under the optimum conditions found; the latter improved PC yields by 12.5% and 47.8%, when compared to freeze-thawing extraction, and bead beater homogenization-based extraction, respectively. UAE successive extractions allowed to valorize other important bioactive compounds than PC, by reusing biomass, supporting a favorable contribution to the economic feasibility of the S. salina-based process towards a biorefinery approach.

Global market and economic analysis of microalgae technology: Status and perspectives

Microalgae have been a promising alternative source of high-value compounds to replace the non-sustainable fossil fuels resource. The recent research development of algae-based bioproducts has remarkable impact various industries section for its renewability, efficiency, and environmentally friendly crops over those synthetic-made product. However, by utilizing microalgae biomass toward their full potential is still limited due to lack of research funding, social acceptability and challenges in policy implementation. This present review highlights the various microalgae biotechnology with consideration of economical aspect for the global potential of algae market, comparison between the microalgae market in Malaysia and international countries. In addition, the cultivation technologies and feasibility of microalgae biomass production globally, followed by insightful challenges and future development of microalgae industry are mentioned. The current study will contribute to the understanding of upstream and downstream of microalgae processing along with technical economical understandings for the successful commercialisation of microalgae products.

Effects of Culture Conditions on the Performance of Arthrospira platensis and Its Production of Exopolysaccharides

Exopolysaccharides (EPS) produced by Arthrospira platensis (A. platensis) has been widely applied in industry and commerce for its various activities but the accumulation of EPS in culture medium may influence the growth of A. platensis reversely. This work aims to explore the impacts of initial pH, nitrogen source and concentration, phosphate concentration and recycle times of the culture medium on the growth of A. platensis and the secretion of its EPS. The results showed that EPS accumulated with the increase in recycle times of culture medium. The optimal initial pH for the growth of A. platensis was 8.50, and high pH of 11.5 inhibited the growth of biomass while resulting in highest EPS content of 92.87 mg/g DW. Excessive and limited nitrogen (NaNO3 of 25.00 g/L and NaNO3 < 2.50 g/L) and phosphate (K2HPO4 of 5.00 g/L and K2HPO4 < 0.50 g/L) inhibited the biomass production of A. platensis by 1.28−30.77% and 14.29−45.05%, respectively. EPS yield of 97.57 mg/g DW and 40.90 mg/g DW were obtained under NaNO3 of 25.00 g/L and K2HPO4 of 5.00 g/L due to salt stress. These findings are beneficial in providing a theoretical basis for high yield EPS from A. platensis without affecting biomass yield.

Growth of Spirulina Maxima in an Optimized Concentric Internal Tube Photobioreactor

BACKGROUND

Microalgae have the potential to generate high-value products. The design of photobioreactors (PBRs), in which microalgae are cultured, is crucial because alterations in their configuration and operational conditions can affect the biomass production and productivity.

OBJECTIVE

The objective of this study was to optimize the diameter of the internal tube of an airlift PBR and to characterize the growth of Spirulina maxima in an optimized design.

MATERIAL AND METHODS

S. maxima was cultured in a mineral medium without an organic carbon source. The PBR consisted of an acrylic cylinder with an operational volume of 7 L. Daily determinations of biomass (by filtration), chlorophyll, N-NO₃ and P-PO₄ (spectrophotometrically) were carried out.

RESULTS

The use of a concentric tube with a diameter of 3 inches led to an increased biomass concentration of 1.14 ± 0.136 g.L_-1, allowing a global biomass productivity of 153 mg.L_-1.d_-1. The culture reached a volumetric consumption velocity of 27.34 ± 1.596 and 2.29 ± 0.353 mg.L_-1.d_-1 for N and P, respectively.

CONCLUSIONS

It was concluded that operational conditions must be specifically selected for each cultivated strain and that this configuration of airlift PBR can produce Spirulina biomass under laboratory conditions with a high biomass productivity.

High Molecular Weight λ-Carrageenan Improves the Color Stability of Phycocyanin by Associative Interactions

Phycocyanin is a protein-chromophore structure present in Arthrospira platensis commonly used as a blue-colorant in food. Color losses of phycocyanin can be reduced by electrostatic complexation with λ-carrageenan. The aim of this study was to investigate the effect of molecular weight (MW) of λ-carrageenan on the color stabilization of electrostatic complexes formed with phycocyanin and λ-carrageenan. Samples were heated to 70 or 90°C at pH 3.0 and stored at 25°C for 14 days. The MW of λ-carrageenan was reduced by ultrasound treatments for 15, 30, 60, and 90 min. Prolonged ultrasonication had a pronounced effect on the Mw, which decreased from 2,341 to 228 kDa (0–90 min). Complexes prepared with low MW λ-carrageenan showed greater color changes compared to complexes prepared with high MW λ-carrageenan. The MW had no visible effect on color stability on day 0, but green/yellow shifts were observed during storage and after heating to 70°C. Medium MW showed less color stabilization effects compared to low MW when heated to 70°C. Moreover, for solutions prepared with ultrasonicated λ-carrageenan, significant hue shifts toward green/yellow, and precipitation were observed after a heat treatment at 90°C. In addition, the sizes of the complexes were significantly reduced (646–102 nm) by using ultrasonicated λ-carrageenan, except for the lowest MW λ-carrageenan when heated to 90°C. Overall, these findings demonstrated that decreasing the MW of λC had adverse effects on the color stability of PC:λC complexes heated to 70 and 90°C.

Biofuel recovery from microalgae biomass grown in dairy wastewater treated with activated sludge: The next step in sustainable production

Microalgae biofuel could be the next step in avoiding the excessive use of fossil fuels and reducing negative impacts on the environment. In the present study, two species of microalgae (Scenedesmus obliquus and Chlorella vulgaris) were used for biomass production, grown in dairy wastewater treated by activated sludge systems. The photobioreactors were operated in batch and in continuous mode. The dry biomass produced was in the range of 2.30 to 3.10 g L^-1. The highest volumetric yields for lipids and carbohydrates were 0.068 and 0.114 g L^-1 day^-1. Maximum CO₂ biofixation (750 mg L^-1 day^-1) was obtained in continuous mode. The maximum values for lipids (21%) and carbohydrates (39%) were recorded in the batch process with species Scenedesmus obliquus. In all of the experiments, the Linolenic acid concentration (C18:3) was greater than 12%, achieving satisfactory oxidative stability and good quality. Projected biofuel production could vary between 4,863,708 kg and 9,246,456 kg year^-1 if all the dairy wastewater produced in Brazil were used for this purpose. Two hectares would be needed to produce 24,99 × 10⁹ L year^-1 of microalgae bioethanol, a far lower value than used in cultivating sugar cane. If all dairy wastewater generated annually in Brazil were used to produce microalgae biomass, it would be possible to obtain approximately 30,609 to 53,647 barrels of biodiesel per year. These data show that only by using dairy wastewater would biofuels be produced to replace 17% to 40% of the fossil fuels currently used in Brazil.

Supplementation With Spirulina Reduces Infarct Size and Ameliorates Cardiac Function in a Pig Model of STEMI

Background and Aims: Myocardial infarction (MI) is the clinical manifestation of atherosclerotic coronary artery disease. Spirulina is an algae known to ameliorate cardiometabolic disorders and with proven anti-inflammatory and anti-oxidant effects. We investigated, in a highly translatable animal model, whether oral supplementation with spirulina protects against the deleterious effects triggered by ST-elevation MI (STEMI). Methods: Pigs were fed a regular diet supplemented with spirulina (1 g/animal/bid) or placebo-control for 10 days. Thereafter, animals were subjected to 1.5 h percutaneous balloon-induced coronary occlusion (STEMI) followed by 2.5 h reperfusion and then sacrificed. We assessed infarct size and cardiac function. Blood samples and infarcted and remote myocardial tissue were obtained. Results: Spirulina supplementation reduced infarct size by 64%, increased myocardial salvage by 18%, and improved cardiac function by 30% vs. controls (p < 0.05). These benefits were associated with attenuation in DNA-oxidative damage and apoptotic markers and increased iNOS in the infarcted myocardium, higher AMPK activation in the remote myocardium, and lower myocardial MCP-1 expression. Systemically, spirulina attenuated Cox-2 expression in STEMI-activated peripheral blood mononuclear cells and enhanced TNF-α release acutely post-STEMI. Additionally, spirulina decreased weight gain progression over time (p < 0.05) without changes in lipids, glucose, liver or kidney parameters. Conclusion: A 10-day supplementation with spirulina exerts cardioprotection in a preclinical setting of STEMI by limiting cardiac damage and improving ventricular contractility through anti-oxidative, anti-inflammatory, and anti-apoptotic mechanisms.

Cyanobacterial biorefinery: Towards economic feasibility through the maximum valorization of biomass

Cyanobacteria are well known for their plethora of applications in the fields of food industry, pharmaceuticals and bioenergy. Their simple growth requirements, remarkable growth rate and the ability to produce a wide range of bio-active compounds enable them to act as an efficient biorefinery for the production of valuable metabolites. Most of the cyanobacteria based biorefineries are targeting single products and thus fails to meet the efficient valorization of biomass. On the other hand, multiple products recovering cyanobacterial biorefineries can efficiently valorize the biomass with minimum to zero waste generation. But there are plenty of bottlenecks and challenges allied with cyanobacterial biorefineries. Most of them are being associated with the production processes and downstream strategies, which are difficult to manage economically. There is a need to propose new solutions to eliminate these tailbacks so on to elevate the cyanobacterial biorefinery to be an economically feasible, minimum waste generating multiproduct biorefinery. Cost-effective approaches implemented from production to downstream processing without affecting the quality of products will be beneficial for attaining economic viability. The integrated approaches in cultivation systems as well as downstream processing, by simplifying individual processes to unit operation systems can obviously increase the economic feasibility to a certain extent. Low cost approaches for biomass production, multiparameter optimization and successive sequential retrieval of multiple value-added products according to their high to low market value from a biorefinery is possible. The nanotechnological approaches in cyanobacterial biorefineries make it one step closer to the goal. The current review gives an overview of strategies used for constructing self-sustainable- economically feasible- minimum waste generating; multiple products based cyanobacterial biorefineries by the efficient valorization of biomass. Also the possibility of uplifting new cyanobacterial strains for biorefineries is discussed.