High value pigment production from Arthrospira (Spirulina) platensis cultured in seawater

Exploitation of inland salt lake water by dilution and nutrient enrichment to cultivate Vischeria sp. WL1 (Eustigmatophyceae) for biomass and oil production

Salt lakes are significant components of global inland waters. Salt lake (SL) water can provide precious mineral resource for microbial growth. The prospect of utilizing diluted SL water for cultivation of a terrestrial oil-producing microalga Vischeria sp. WL1 was evaluated under laboratory conditions. Based on the detected mineral element composition, the water from Gouchi Salt Lake was diluted 2, 4, 6 and 8 folds and used with supplementation of additional nitrogen, phosphorus and iron (SL+ water). It was found that 4 folds diluted SL+ water was most favorable for biomass and oil production. When cultivated in this condition, Vischeria sp. WL1 gained a biomass yield of 0.82 g L-1 and an oil yield of 0.56 g L-1 after 24 days of cultivation, which is comparable to the optimum productivity we previously established. In addition, total monounsaturated fatty acid contents (64.4∼68.1 %) of the oils resulted from cultures in diluted SL+waters were higher than that in the control (55.5 %). It was also noteworthy that in all these cultures the oil contents (652.0∼681.0 mg g-1) accounted for the most of the biomass, which are far more than the protein and starch contents. This study demonstrates the feasibility of using SL water as a cost-effective mineral resource to cultivate microalgae for biomass and oil production.

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.

Impacts of selenium nanoparticles and spirulina alga to alleviate the deleterious effects of heat stress on reproductive efficiency, oxidative capacity and immunity of doe rabbits

Effects of dietary inclusion of spirulina platensis (SP) and selenium nanoparticles (SeNPs) combination (SP-SeNPs) on the reproductive performance in vivo and in vitro, reproductive and metabolic hormones, hemato-bichemical parameters, oxidative stress, and immunity of heat-stressed doe rabbis were evaluated. All supplements significantly increased live litter size at birth and weaning, viability rate at birth, hemoglobin and red blood cells, and plasma T3, T4, insulin, total proteins and albumin compared with control. Plasma estradiol 17-β (pre-mating), progesterone (mid-pregnancy), and prolactin (day -7 postpartum) were significantly increased only by SeNPs (0.3, 0.4, and 0.5 mg/kg). All dietary supplements significantly reduced WBCs, cortisol, lipid profile, and improved liver and kidney functions. Immunoglobulins levels, antioxidants capacity were significantly increased, superoxide dismutase was increased by SeNPs (0.4 and 0.5 mg/kg), while malondialdehyde was reduced by 0.3, 0.4 and 0.5 SeNPs mg/kg. Sexual receptivity, pregnancy rate, viability rate at weaning, ovulation rate, and embryo quality were significantly increased by increasing SeNPs above 0.1 mg, while embryo yield was increased by >0.2 mg SeNPs/kg. A combination of SP and SeNPs, could be potentially used as a strong antioxidant to enhance heat regulation and doe rabbit reproduction via improving reproductive and metabolic hormones, antioxidant status and immunological parameters.

Microalgae-assisted green bioremediation of food-processing wastewater: A sustainable approach toward a circular economy concept

Wastewater disposal is a major environmental issue that pollutes water, causing eutrophication, habitat destruction, and economic impact. In Mexico, food-processing effluents pose a huge environmental threat due to their excessive nutrient content and their large volume discharged every year. Some of the most harmful residues are tequila vinasses, nejayote, and cheese whey. Each liter of tequila generates 13-15 L of vinasses, each kilogram of cheese produces approximately 9 kg of cheese whey, and each kilogram of nixtamalized maize results in the production of 2.5-3.3 L of nejayote. A promising strategy to reduce the contamination derived from wastewater is through microalgae-based wastewater treatment. Microalgae have a high adaptability to hostile environments and they can feed on the nutrients in the effluents to grow. Moreover, to increase the viability, profitability, and value of wastewater treatments, a microalgae biorefinery could be proposed. This review will focus on the circular bioeconomy scheme focused on the simultaneous food-processing wastewater treatment and its use to grow microalgae biomass to produce added-value compounds. This strategy allows for the revalorization of wastewater, decreases contamination of water sources, and produces valuable compounds that promote human health such as phycobiliproteins, carotenoids, omega-3 fatty acids, exopolysaccharides, mycosporine-like amino acids, and as a source of clean energy: biodiesel, biogas, and bioethanol.

Enhanced phycocyanin production from Spirulina subsalsa via freshwater and marine cultivation with optimized light source and temperature

To find out optimum and cost-efficient strategy for phycocyanin production, the effect of light source and temperature on Spirulina subsalsa growth were studied in chemically defined freshwater medium and seawater supplied with wastewater from glutamic acid fermentation tank. Maximum growth rate and the highest phycocyanin content were obtained by 35 °C and green light, respectively. A two-stage cultivation strategy was proposed and applied, which combines biomass accumulation at 35 °C and phycocyanin synthesis simulated under green light. As a result, phycocyanin production reached 70 mg/L/d and 11 mg/L/d from freshwater and seawater medium, respectively. With all tested conditions, a strong correlation between biomass and phycocyanin/chlorophyll ratio, rather than phycocyanin, revealed the dependence of Spirulina subsalsa growth on coordinating regulation of photosynthetic pigments. The relationship between growth and phycocyanin production under various light and temperature can be a good basis for improving phycocyanin production from Spirulina subsalsa with or without freshwater consumption.

Exploitation of renewable energy sources for water desalination using biological tools

The emerging impacts of climate change and the growing world population are driving the demand for more food resources and creating an urgent need for new water resources. About 93% of Earth's surface is made up of water bodies, mainly oceans. Seawater attracted a lot of attention in order to be used as a sustainable source of usable water. However, an essential step in harnessing this source of water is desalination. Utilizing renewable sources of energy, biology offers several tools for removal of salts. This article for the first time reviews all currently available biological water desalination tools and compares their efficiency with industrial systems. Bacteria are employed as electrical power generators to provide the energy needed for desalination in microbial desalination cells. Its salt removal efficiency varied from 0.8 to 30 g/L/d. Many strains of algal cells can grow in high concentrations of salts, adsorb and accumulate it inside the cell, and therefore could be used without prior treatment for seawater desalination. This biological tool can yield salt removal efficiency of 0.4-5 g/L/d. Biopolymers are also used for treatment of seawater through enhancing water evaporation as a component of solar steam generators. Despite significant advances in biological water desalination, further modifications and improvements are still needed to make its use sustainable and cost-effective.

Production of Arthrospira platensis: Effects on Growth and Biochemical Composition of Long-Term Acclimatization at Different Salinities

Arthrospira platensis is an edible cyanobacterium with high nutritional value. Even though A. platensis is not a marine species, it can be adapted to higher salinities, a strategy that could allow mass cultivation using brackish or saline water. In this work A. platensis was long-term adapted at different salinities (5-60 g/L NaCl added as natural sea salt) to evaluate the growth and biochemical composition of the biomass produced. Biomass production was enhanced in salinity up to 40 g/L NaCl, while at 60 g/L NaCl biomass production slightly decreased. However, it displayed higher values compared to the conventional Zarrouk growth medium. By increasing the salinity, carbohydrate content increases, while proteins, phycocyanin, carotenoids, and total phenolics decreased. Biomass content in lipids, and chlorophyll along with the antioxidant capacity of extracts, was not significantly affected. A. platensis tended to increase the unsaturated fatty acids, while amino acid composition was not significantly affected by the increased salinity. However, in vitro protein digestibility was negatively affected when salinity was above 20 g/L NaCl. It was macroscopically observed that trichomes were longer at higher salinities, and especially at 40 g/L NaCl. The results suggest that A. platensis when acclimated in long-term can be grown successfully at various salinities.

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.

Sustainable Production of Pigments from Cyanobacteria

Pigments are intensely coloured compounds used in many industries to colour other materials. The demand for naturally synthesised pigments is increasing and their production can be incorporated into circular bioeconomy approaches. Natural pigments are produced by bacteria, cyanobacteria, microalgae, macroalgae, plants and animals. There is a huge unexplored biodiversity of prokaryotic cyanobacteria which are microscopic phototrophic microorganisms that have the ability to capture solar energy and CO2 and use it to synthesise a diverse range of sugars, lipids, amino acids and biochemicals including pigments. This makes them attractive for the sustainable production of a wide range of high-value products including industrial chemicals, pharmaceuticals, nutraceuticals and animal-feed supplements. The advantages of cyanobacteria production platforms include comparatively high growth rates, their ability to use freshwater, seawater or brackish water and the ability to cultivate them on non-arable land. The pigments derived from cyanobacteria and microalgae include chlorophylls, carotenoids and phycobiliproteins that have useful properties for advanced technical and commercial products. Development and optimisation of strain-specific pigment-based cultivation strategies support the development of economically feasible pigment biorefinery scenarios with enhanced pigment yields, quality and price. Thus, this chapter discusses the origin, properties, strain selection, production techniques and market opportunities of cyanobacterial pigments.

Inputs don't equal outputs: bacterial microbiomes of the ingesta, gut, and feces of the keystone deposit feeder Ilyanassa obsoleta

Bacteria drive energy fluxes and geochemical processes in estuarine sediments. Deposit-feeding invertebrates alter the structure and activity of microbial communities through sediment ingestion, gut passage, and defecation. The eastern mud snail, Ilyanassa obsoleta, is native to estuaries of the northwestern Atlantic, ranging from Nova Scotia, Canada, to Florida in the USA. Given extremely high densities, their deposit-feeding and locomotory activities exert ecological influence on other invertebrates and microbes. Our aim was to characterize the bacterial microbiome of this 'keystone species' and determine how its feeding alters the native bacterial microbiota. We gathered snails from both mudflat and sandflat habitats and collected their fresh fecal pellets in the laboratory. Dissection of these same snails allowed us to compare bacterial assemblages of ingested sediments, shell surfaces, gut sections (esophagus, stomach, intestine), and feces using DNA metabarcoding. Our findings indicate a diverse, resident gut microbiota. The stomach and intestines were dominated by bacteria of the genus Mycoplasma. Comparison of ingesta and feces revealed digestion of several bacterial taxa, introduction of gut residents during passage, in addition to unique bacterial taxa within the feces of unknown provenance. Our results demonstrate that I. obsoleta has the potential to modify microbial community structure in estuarine sediments.

Natural Substrates and Culture Conditions to Produce Pigments from Potential Microbes in Submerged Fermentation

Pigments from bacteria, fungi, yeast, cyanobacteria, and microalgae have been gaining more demand in the food, leather, and textile industries due to their natural origin and effective bioactive functions. Mass production of microbial pigments using inexpensive and ecofriendly agro-industrial residues is gaining more demand in the current research due to their low cost, natural origin, waste utilization, and high pigment stimulating characteristics. A wide range of natural substrates has been employed in submerged fermentation as carbon and nitrogen sources to enhance the pigment production from these microorganisms to obtain the required quantity of pigments. Submerged fermentation is proven to yield more pigment when added with agro-waste residues. Hence, in this review, aspects of potential pigmented microbes such as diversity, natural substrates that stimulate more pigment production from bacteria, fungi, yeast, and a few microalgae under submerged culture conditions, pigment identification, and ecological functions are detailed for the benefit of industrial personnel, researchers, and other entrepreneurs to explore pigmented microbes for multifaceted applications. In addition, some important aspects of microbial pigments are covered herein to disseminate the knowledge.

The Effects of Dietary Arthrospira platensis on Oxidative Stress Response and Pigmentation in Yellow Catfish Pelteobagrus fulvidraco

In aquaculture, fish are often exposed to several stress conditions, which will cause oxidative disorder and bring about health and quality problems. Arthrospira platensis contains abundant bioactive ingredients, which are beneficial for animal health. This study was conducted to investigate the effects of A. platensis on pigmentation, antioxidant capacity, and stress response after air exposure of fish. A total of 120 yellow catfish Pelteobagrus fulvidraco (initial weight 70.19 ± 0.13 g) were divided into three tanks per treatment and fed diets supplemented with 0 g kg−1 A. platensis (CON) and 20 g kg −1 A. platensis (AP) for 65 days. The results indicated that dietary A. platensis had no effects on the growth of yellow catfish. The AP diet significantly reduced lactic acid (LD) and cortisol levels stimulated by air exposure stress (p < 0.05). Dietary A. platensis significantly increased plasma superoxide dismutase (SOD) and glutathione peroxidase (GPX) activities and glutathione (GSH) contents, and the relative expression levels of sod and cat, to protect against oxidative stress caused by air exposure (p < 0.05). The AP diet significantly improved the relative expression level of nrf2 (nuclear factor erythroid-2 related factor 2), while the relative expression level of keap1 (kelch-like ECH associated protein 1) was downregulated, and the protein levels of liver Nrf2 were significantly increased after air exposure stimuli (p < 0.05). Dietary A. platensis significantly increased skin lutein contents, increased skin redness, yellowness and chroma (p < 0.05), and improved body color abnormalities after oxidative stress caused by air exposure stimuli. Skin yellowness was associated with lutein contents and the expression levels of some antioxidant genes to varying degrees. Overall, dietary A. platensis could be utilized as a feed additive to activate the antioxidant response, as well as alleviate oxidative stress and pigmentation disorder induced by air exposure.

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.

Rapid green microwave assisted extraction of lutein from Chlorella sorokiniana (NIOT-2) - Process optimization

Chloropycean microalgae are looked up as a prospective alternate source for the production of xanthophyll carotenoid lutein. Despite, the market significance and multitude of nutraceutical applications of lutein commercial production from microalgae still remains a challenge due to the prohibitive downstream cost. This necessitates innovative less energy intensive, high lutein yielding green processes. The present work presents a comprehensive study on the rapid green microwave assisted extraction (MAE) of lutein from marine chlorophycean microalgae Chlorella sorokiniana (NIOT-2). The process parameters of microwave assisted alkali pre-treatment like exposure time (ET), alkali concentration (AC) and solid (biomass): liquid (aqueous Potassium hydroxide-KOH) ratio (S: L ratio) were optimized using single factor and response surface method (RSM) experiments. The optimized conditions for microwave assisted alkali pre-treatment (ET:1.47 min; AC: 8.16 M KOH and S:L ratio of 36.8:1 (mg/mL) augmented the lutein yield (20.69 ± 1.2 mg/g) 3.26 fold when compared to conventional extraction (6.35 ± 0.44 mg/g). Lutein extracted using optimized MAE conditions was purified and characterized. Visualization of the MAE extracted algal biomass using Scanning electron microscope confirmed the effective cell disruption. X-ray diffraction (XRD) analysis of microwave assisted alkali treated biomass (83.85%) revealed a significantly higher crystallinity index when compared to untreated control (17.28%). MAE pre-treatment can thus be propounded as a suitable process for lutein extraction from marine microalgae due to its amalgamated rapidity, homogenous heating, less energy intensiveness and high extraction yield.

Modeling and Optimizing the Effect of Light Color, Sodium Chloride and Glucose Concentration on Biomass Production and the Quality of Arthrospira platensis Using Response Surface Methodology (RSM)

Arthrospira platensis (Spirulina) biomass is a valuable source of sustainable proteins, and the basis for new food and feed products. State-of-the-art production of Spirulina biomass in open pond systems only allows limited control of essential process parameters, such as light color, salinity control, or mixotrophic growth, due to the high risk of contaminations. Closed photobioreactors offer a highly controllable system to optimize all process parameters affecting Spirulina biomass production (quantity) and biomass composition (quality). However, a comprehensive analysis of the impact of light color, salinity effects, and mixotrophic growth modes of Spirulina biomass production has not been performed yet. In this study, Response Surface Methodology (RSM) was employed to develop statistical models, and define optimal mixotrophic process conditions yielding maximum quantitative biomass productivity and high-quality biomass composition related to cellular protein and phycocyanin content. The individual and interaction effects of 0, 5, 15, and 30 g/L of sodium chloride (S), and 0, 1.5, 2, and 2.5 g/L of glucose (G) in three costume-made LED panels (L) where the dominant color was white (W), red (R), and yellow (Y) were investigated in a full factorial design. Spirulina was cultivated in 200 mL cell culture flasks in different treatments, and data were collected at the end of the log growth phase. The lack-of-fit test showed that the cubic model was the most suitable to predict the biomass concentration and protein content, and the two-factor interaction (2FI) was preferred to predict the cellular phycocyanin content (p > 0.05). The reduced models were produced by excluding insignificant terms (p > 0.05). The experimental validation of the RSM optimization showed that the highest biomass concentration (1.09, 1.08, and 0.85 g/L), with improved phycocyanin content of 82.27, 59.47, 107 mg/g, and protein content of 46.18, 39.76, 53.16%, was obtained under the process parameter configuration WL4.28S2.5G, RL10.63S1.33G, and YL1.00S0.88G, respectively.

Synergistic effect of Spirulina platensis and selenium nanoparticles on growth performance, serum metabolites, immune responses, and antioxidant capacity of heat-stressed broiler chickens

This study examined the effects of dietary Spirulina platensis (SP) at levels of 0, 5, and 10 g.kg^-1 and selenium nanoparticles (SeNPs) at 0, 0.1, and 0.2 mg.kg^-1, individually and in combination, on heat-stressed broiler chickens for 5 weeks. Four hundred fifty one-day-old Ross-308 chicks were allocated to 9 dietary groups with 5 replicates (10 chicks each). The control diet was consisted of corn-soybean-based basal diet. The obtained results displayed a significant increase in final body weight (p = 0.005) and weight gain during the periods from 22 to 35 days (p = 0.002) and 1 to 35 days (p = 0.005) in birds fed supplemented diets compared to those fed control diet, with the highest being in birds fed with both 10 g SP and 0.1 mg SeNPs. Feed conversion ratio was also improved in birds fed supplemented compared to control group. Dietary supplements significantly improved carcass dressing (p < 0.001), carcass yield (p = 0.001) percentages, and blood lipid profile. Blood triiodothyronine was higher (p = 0.005) with all treated diets except that contain 5 g SP compared to the control, with the highest being in birds fed diet contains 5 g SP + 0.2 mg SeNPs. Immunoglobulin subclasses IgG, IgM, and IgA were higher in birds fed supplemented diets compared to the control group. Antibody titers to Newcastle disease, avian influenza, and infectious bursal disease were numerically increased with dietary supplementation compared to the control group. Dietary treatments increased (p < 0.001) glutathione peroxidase and superoxide dismutase (SOD) levels, except diet contains 5 g SP for SOD level and decreased (p < 0.001) malondialdehyde level. It is concluded that dietary inclusion of SP and SeNPs, particularly their combination at levels 5 g SP plus 0.2 mg SeNPs kg^-1 and 10 g SP plus 0.1 mg SeNPs kg^-1, improved growth performance, carcass yield, immunity, and antioxidant capacity of heat-stressed broilers.

Innovative application of brackish groundwater without the addition of nutrients in the cultivation of Spirulina and Chlorella for carbohydrate and lipid production

Brackish groundwater is promising for the cultivation of economically important microalgae; however, its effects have been evaluated only after nutrient supplementation. In this study, 100% brackish groundwater was evaluated as a culture medium for Spirulina sp. (BGWS) and Chlorella fusca (BGWC). In addition, the effects of supplementation with 25% of the nutrients from Zarrouk (BGWS25) and BG-11 (BGWC25) culture media were evaluated. BGWS and BGWC increased the concentration (68.1% w w^-1) and productivity of carbohydrate (35.3 mg L^-1 d^-1) in Spirulina sp. and increased the concentration (56.4% w w^-1) and productivity (13.5 mg L^-1 d^-1) of lipids in C. fusca biomass, when compared to that in the respective controls. The use of brackish groundwater as the sole culture medium is an innovative alternative for the economic production of biomass rich in carbohydrates and lipids. This has potential applications for biofuel production.

Towards a general kinetic microalgae model: Extending a semi-deterministic green microalgae model for the cyanobacterium Arthrospira platensis and red alga Porphyridium purpureum

Mathematical models for microalgae and cyanobacteria are seldomly validated for different algal species, as such limiting their applicability. Therefore, in this research, a previously developed kinetic model describing the growth of the green microalgae species Chlorella vulgaris was used to simulate the growth of the cyanobacterium Arthrospira platensis and the red alga Porphyridium purpureum. Based on a global sensitivity analysis, the model parameter µ_max,A was calibrated using respirometric-titrimetric data. Calibration yielded values of 5.76 ± 0.17 d^-1, 2.06 ± 0.16 d^-1 and 1.06 ± 0.09 d^-1 for Chlorella vulgaris, Arthrospira platensis and Porphyridium purpureum, respectively. Model simulations revealed that the biological growth equations in this model are adequate. However, increased light intensities triggered a survival mechanism for Arthrospira platensis, which is currently not taken into account by the model, leading to bad model accuracy under these circumstances. Future work should address the most important survival mechanisms and include those in the model to widen its applicability.

Expression of heat-resistant β-glucosidase in Escherichia coli and its application in the production of gardenia blue

Gardenia blue is a natural blue pigment that is environmentally friendly, non-toxic, and stable. The hydrolysis of geniposide, catalyzed by β-glucosidase, is a critical step in the production process of gardenia blue. However, β-glucosidase is not resistant to high temperatures, limiting the production of gardenia blue. In this study, we investigated the effectiveness of a heat-resistant glucosidase obtained from Thermotoga maritima in the production of gardenia blue. The enzyme exhibited a maximum activity of 10.60 U/mL at 90 °C. Single-factor and orthogonal analyses showed that exogenously expressed heat-resistant glucosidase reacted with 470.3 μg/mL geniposide and 13.5 μg/mL glycine at 94.2 °C, producing a maximum yield of 26.2857 μg/mL of gardenia blue after 156.6 min. When applied to the dyeing of denim, gardenia blue produced by this method yielded excellent results; the best color-fastness was achieved when an iron ion mordant was used. This study revealed the feasibility and application potential of microbial production of gardenia blue.

Living to the High Extreme: Unraveling the Composition, Structure, and Functional Insights of Bacterial Communities Thriving in the Arsenic-Rich Salar de Huasco Altiplanic Ecosystem

Microbial communities inhabiting extreme environments such as Salar de Huasco (SH) in northern Chile are adapted to thrive while exposed to several abiotic pressures and the presence of toxic elements such as arsenic (As). Hence, we aimed to uncover the role of As in shaping bacterial composition, structure, and functional potential in five different sites in this altiplanic wetland using a shotgun metagenomic approach. The sites exhibit wide gradients of As (9 to 321 mg/kg), and our results showed highly diverse communities and a clear dominance exerted by the Proteobacteria and Bacteroidetes phyla. Functional potential analyses show broadly convergent patterns, contrasting with their great taxonomic variability. As-related metabolism, as well as other functional categories such as those related to the CH4 and S cycles, differs among the five communities. Particularly, we found that the distribution and abundance of As-related genes increase as the As concentration rises. Approximately 75% of the detected genes for As metabolism belong to expulsion mechanisms; arsJ and arsP pumps are related to sites with higher As concentrations and are present almost exclusively in Proteobacteria. Furthermore, taxonomic diversity and functional potential are reflected in the 12 reconstructed high-quality metagenome assembled genomes (MAGs) belonging to the Bacteroidetes (5), Proteobacteria (5), Cyanobacteria (1), and Gemmatimonadetes (1) phyla. We conclude that SH microbial communities are diverse and possess a broad genetic repertoire to thrive under extreme conditions, including increasing concentrations of highly toxic As. Finally, this environment represents a reservoir of unknown and undescribed microorganisms, with great metabolic versatility, which needs further study. IMPORTANCE As microbial communities inhabiting extreme environments are fundamental for maintaining ecosystems, many studies concerning composition, functionality, and interactions have been carried out. However, much is still unknown. Here, we sampled microbial communities in the Salar de Huasco, an extreme environment subjected to several abiotic stresses (high UV radiation, salinity and arsenic; low pressure and temperatures). We found that although microbes are taxonomically diverse, functional potential seems to have an important degree of convergence, suggesting high levels of adaptation. Particularly, arsenic metabolism showed differences associated with increasing concentrations of the metalloid throughout the area, and it effectively exerts a significant pressure over these organisms. Thus, the significance of this research is that we describe highly specialized communities thriving in little-explored environments subjected to several pressures, considered analogous of early Earth and other planets, that have the potential for unraveling technologies to face the repercussions of climate change in many areas of interest.

Effect of various light spectra on amino acids and pigment production of Arthrospira platensis using flat-plate photobioreactor

Today, the use of nutrients derived from natural bioactive compounds application in the food, pharmaceutical, and cosmetic industries is on the increase. This paper aimed to evaluate the amino acids profile (essential and non-essential) and pigments composition (chlorophyll a, carotenoids, and phycocyanin) of Arthrospira platensis (a blue-green microalga) cultivation in a flat-plate photobioreactor under various types of light-emitting diodes (red: 620-680 nm, white: 380-780 nm, yellow: 570-600nm, blue: 445-480 nm). The maximum biomass concentration (604.96 mg L-1) occurred when the red LED was applied for cultivation, and the minimum biomass concentration (279.39 mg L-1) was obtained under blue LED. The sequence of pigments and amino acids concentrations (mg L-1culture volume) was approximately in accordance with the biomass productivity. It means the red light produces the maximum concentration of pigments (chlorophyll a: 5.42, carotenoids: 2.92, phycocyanin: 67.54 mg L-1) and amino acids (essential amino acids: 110.47, nonessential amino acids: 179.10 mg L-1). Nevertheless, when these values were measured in mg per g of dry weight, the utmost contents were observed in microalgal products cultivated under blue LED. These consequences are due to the highest cell productivity and the most extended length of cells that occurred under red and blue LEDs, respectively.

Can selenium-enriched spirulina supplementation ameliorate sepsis outcomes in selenium-deficient animals?

In intensive care units, sepsis is the first cause of death. In this pathology, inflammation and oxidative status play a crucial role in patient outcomes. Interestingly, 92% of septic patients exhibit low selenium plasma concentrations (a component of antioxidant enzymes). Moreover, Spirulina platensis, a blue-green algae, demonstrated anti-inflammatory effects. In this context, the main purpose of our study was to analyze the effect of a selenium-enriched spirulina after a selenium deficiency on sepsis outcome in rats. Sixty-four rats were fed 12 weeks with a selenium-deficient food. After 8 weeks, rats were supplemented (via drinking water) for 4 weeks with sodium selenite (Se), spirulina (Spi), or selenium-enriched spirulina (SeSp). Sepsis was then induced by cecal ligature and puncture, and survival duration was observed. The plasma selenium concentration was measured by ICPMS. Expression of GPx1 and GPx3 mRNA was measured by RT-PCR. Blood parameters (lactates and HCO3- concentrations, pH, PO2 , and PCO2 ) were analyzed at 0, 1, and 2 h as well as inflammatory cytokines (IL-6, TNF-α, IL-10). Sodium selenite and SeSP supplementations restored plasma selenium concentration prior to sepsis. The survival duration of SeSP septic rats was significantly lower than that of selenium-supplemented ones. Gpx1 mRNA was increased after a selenium-enriched spirulina supplementation while Gpx3 mRNA levels remained unchanged. Furthermore, sodium selenite prevented sepsis-induced acidosis. Our results show that on a basis of a Se deficiency, selenium-enriched spirulina supplementations significantly worsen sepsis outcome when compared to Se supplementation. Furthermore, Se supplementation but not selenium-enriched spirulina supplementation decreased inflammation and restored acid-base equilibrium after a sepsis induction.

A critical look into different salt removal treatments for the production of high value pigments and fatty acids from marine microalgae Chlorella vulgaris (NIOT-74)

The prime challenge in seawater culture of microalgae for high value biomolecules production is presence of salt. Hence, twelve different salt removal treatments were evaluated for their impact on the lutein, total carotenoid, chlorophyll yields and fatty acid profile of marine microalgae Chlorella vulgaris (NIOT-74). The effectiveness of different treatments on salt removal was also visualized with the aid of Scanning Electron Microscope (SEM). Among the tested treatments, washing the algal biomass with 0.5 % HCl augmented the lutein (11.56 mg/g) and total carotenoid yield (60.88 mg/g) 1.82 and 1.86 fold respectively, in comparison to untreated control. Highest chlorophyll content (30.64 mg/g) was noticed in the distilled water wash treatment. Different salt removal treatments also impacted the fatty acid profile and degree of unsaturation of the fatty acids significantly. This study thus, signified the importance of salt removal treatments for the commercial production of biomolecules from marine microalgae cultured in natural seawater.

Spirulina sp. LEB 18 cultivation in seawater and reduced nutrients: Bioprocess strategy for increasing carbohydrates in biomass

This study aimed to evaluate the growth and production of biomolecules by Spirulina sp. LEB 18 cultivated in seawater. The seawater was used without nutrient addition (SW0) and supplemented with 100% (SW100), 50% (SW50), and 25% (SW25) nitrogen, phosphorus, iron, and EDTA concentrations that make up the Zarrouk culture medium. When grown in SW0, Spirulina sp. LEB 18 showed maximum biomass concentration (2.17 g L^-1) on the 11th d of cultivation and an increase in the carbohydrate content and productivity by 203% and 52%, respectively, when compared to the control culture. This cultivation strategy demonstrated the feasibility of using seawater as an alternative to freshwater in cultures as well as reduced nutritional requirements for biomass and carbohydrate production.

Engineering salt tolerance of photosynthetic cyanobacteria for seawater utilization

Photosynthetic cyanobacteria are capable of utilizing sunlight and CO₂ as sole energy and carbon sources, respectively. With genetically modified cyanobacteria being used as a promising chassis to produce various biofuels and chemicals in recent years, future large-scale cultivation of cyanobacteria would have to be performed in seawater, since freshwater supplies of the earth are very limiting. However, high concentration of salt is known to inhibit the growth of cyanobacteria. This review aims at comparing the mechanisms that different cyanobacteria respond to salt stress, and then summarizing various strategies of developing salt-tolerant cyanobacteria for seawater cultivation, including the utilization of halotolerant cyanobacteria and the engineering of salt-tolerant freshwater cyanobacteria. In addition, the challenges and potential strategies related to further improving salt tolerance in cyanobacteria are also discussed.

A two-enzyme constituted mixture to improve the degradation of Arthrospira platensis microalga cell wall for monogastric diets

The main goal of this study was to test a rational combination of pre‐selected carbohydrate‐active enzymes (CAZymes) and sulphatases, individually or in combination, in order to evaluate its capacity to disrupt Arthrospira platensis cell wall, allowing the release of its valuable nutritional bioactive compounds. By the end, a two‐enzyme constituted mixture (Mix), composed by a lysozyme and a α‐amylase, was incubated with A. platensis suspension. The microalga cell wall disruption was evaluated through the amount of reducing sugars released from the cell wall complemented with the oligosaccharide profile by HPLC. An increase of the amount of reducing sugars up to 2.42 g/L in microalgae treated with the Mix relative to no treatment (p < .05), as well as a 7‐fold increase of oligosaccharides amount (p < .001), were obtained. With resort of fluorescence microscopy, a 36% reduction of fluorescence intensity (p < .001) was observed using Calcofluor White staining. In the supernatant, the Mix caused a 1.34‐fold increase in protein content (p = .018) relative to the control. Similarly, n‐6 polyunsaturated fatty acids (PUFA) (p = .007), in particular 18:2n‐6 (p = .016), monounsaturated fatty acids (MUFA) (p = .049) and chlorophyll a (p = .025) contents were higher in the supernatant of microalgae treated with the enzyme mixture in relation to the control. Taken together, these results point towards the disclosure of a novel two‐enzyme mixture able to partial degrade A. platensis cell wall, improving its nutrients bioavailability for monogastric diets with the cost‐effective advantage use of microalgae in animal feed industry.

Potential use of a thermal water cyanobacterium as raw material to produce biodiesel and pigments

Global energy demand is increasing every day and most is still derived from non-renewable sources. Therefore, sustainable alternatives are sought to produce biofuels, such as biodiesel. Several studies have demonstrated the potential of microalgae and cyanobacteria to produce biodiesel and pigments. These pigments, such as lutein and astaxanthin, have a high commercial value and can economically support the production of biodiesel. However, few studies have explored the potential of cyanobacteria collected in thermal water. In these microorganisms, both biomass and metabolites production can be altered by the culture form. Thus, a cosmopolitan filamentous cyanobacterium (Geitlerinema amphibium) from thermal water was collected and isolated to evaluate its potential to produce fatty acids, biodiesel, and pigments in two culture media. G. amphibium was cultured in WC (Wright's Cryptophyte) and BBM (Bold's Basal Medium) media. Thermal stress (40 °C for 48 h) was applied to the medium, which generated higher productivity of the biomass in BBM. The cyanobacterium contained higher biodiesel content in the WC medium and higher pigment content in the BBM medium. Thermal stress increased the biodiesel content by 350%, but decreased pigment content. Two pigments with high commercial value (astaxanthin and lutein) were identified. G. amphibium produced up to 2.74 mg g^-1 of astaxanthin and 5.49 mg g^-1 of lutein, which is seven times more lutein than Marigold, currently the main raw material used commercially. Therefore, G. amphibium has the potential to produce biodiesel, astaxanthin, and lutein concomitantly.

Solid Matrix-Supported Supercritical CO₂ Enhances Extraction of γ-Linolenic Acid from the Cyanobacterium Arthrospira (Spirulina) platensis and Bioactivity Evaluation of the Molecule in Zebrafish

Marine cyanobacteria represent a large untapped source of functional glycolipids enriched with polyunsaturated fatty acids (PUFAs) for human health. However, advanced methods for scalable isolation of diverse species containing high-purity PUFA-rich glycolipids will have to be developed and their possible pharmaceutical and nutraceutical functions identified. This paper introduces a novel solid matrix-supported supercritical CO₂ extraction method for scalable isolation of the PUFA γ-linolenic acid (GLA)-enriched glycolipids from the cyanobacterium Arthrospira (Spirulina) platensis, which has been the most widely used among microalgae in the nutraceutical and pharmaceutical industries. Of various porous materials studied, diatomite was the best to facilitate extraction of GLA-rich glycolipids, resulting in an extraction efficiency of 98%. Gamma-linolenic acid made up 35% of total fatty acids (TFAs) in the extracts, which was considerably greater than that obtained with ethanol (26%), Bligh and Dyer (24%), and in situ transesterification (24%) methods, respectively. Lipidomics analysis revealed that GLA was exclusively associated with galactolipids. Pharmaceutical functions of GLA-rich galactolipids were investigated on a zebrafish caudal fin regeneration model. The results suggested that GLA extracted from A. platensis possessed anti-oxidative, anti-inflammatory, and anti-allergic activities, which acted in a concerted manner to promote post-injury regeneration of zebrafish.

Effect of Fermented Spirulina maxima Extract on Cognitive-Enhancing Activities in Mice with Scopolamine-Induced Dementia

This work provides the first demonstration that Spirulina maxima extract fermented with the lactic acid bacterium Lactobacillus planetarium HY-08 has the ability to ameliorate scopolamine-induced memory impairment in mice. The fermented extract exhibited good cognitive-enhancing activities, as demonstrated through Morris water maze and passive avoidance experiments: in these tests, the mice administered the fermented extract at a dose of 400 mg/kg exhibited an escape latency time and a latency time of 88.5 and 76.0 sec, respectively, whereas those administered donepezil, which was used as a positive control, showed an escape latency time and a latency time of 81.3 and 83.3 sec, respectively. However, an extract of 200 mg/kg was considered economically feasible for maintaining relatively high memory-improving activities because only a slight difference in activities was found between 200 and 400 mg/kg. The study also provides the first demonstration that β-carotene, one of the major bioactive substances in S. maxima, has memory-enhancing activity. A detailed analysis of the mechanism for the cognitive-enhancing activities of the fermented extract revealed that the fermented extract effectively increased the phosphorylation of both extracellular signal-regulated kinases (p-ERK) and p-cAMP response element-binding protein (p-CREB) and sequentially upregulated the expression of brain-derived neurotrophic factor (BDNF), whose signaling pathway responds to a reduction in oxidative stress in the brain. The results indicate that the improved efficacy of the fermented extract was likely due to the synergistic effects of β-carotene and other bioactive substances. Therefore, it can be concluded that the fermented extract exerts memory-improving effects in the hippocampus of scopolamine-treated mice through an initial increase in ERK signaling and a sequential induction of the expression of p-CREB and BDNF, and these effects are related to the antioxidant activities of β-carotene and other components.

Embedding photosynthetic biorefineries with circular economies: Exploring the waste recycling potential of Arthrospira sp. to produce high quality by-products

This study was conducted with the aim of embedding circular economies (waste recycling) with photosynthetic biorefineries, for production of commercially viable by-products. Since nitrogen source constitute the major input costs for commercial Arthrospira sp. production, the use of nitrogen rich wastewater for Arthrospira sp. cultivation could significantly reduce their production costs. This study evaluated the effects of high concentrations (8.5-120 mM) of alternative nitrogen sources (urea, ammonium and nitrite) on the biochemical, pigment and proteomic profile of Arthrospira sp., under batch and continuous conditions. Arthrospira sp. cells fed with urea were quantified with modified biochemical and proteomic profile compared to the nitrate fed cells. No inhibitory effect of urea was observed on the biomass even at 120 mM. Nitrite fed cells exhibited comparable biochemical and proteomic profiles as nitrate fed cells. These results clearly indicated at the possibility of using urea rich wastewater streams for profitable cultivation of Arthrospira sp.

Assessment of transient effects of alternative nitrogen sources in continuous cultures of Arthrospira sp. using proteomic, modeling and biochemical tools

The ability of cyanobacterium Arthrospira sp. to assimilate waste nitrogen sources (ammonium and urea) makes it an important candidate for wastewater management. The aim of this work was to evaluate a cultivation approach based on continuous-transitional-feeding regime (nitrate-ammonium-nitrate) in a photobioreactor to assess the effects of ammonium salts on Arthrospira sp. PCC 8005 metabolism. Using a comprehensive biochemical, proteomic and stoichiometric profiling of biomass, this study demonstrated that the proposed cultivation approach could increase the proteins and pigments yields by 20-30%, compared to the respective yields obtained from wild-type Arthrospira sp. strain A light-energy-transfer model was used to predict the biomass and oxygen productivities of Arthrospira sp. cultivated under transitional-feeding regime. 95 ± 2% match was observed between the experimental and simulated productivities. This study thus opened new avenues for use of ammonium rich wastewater for commercial production of high value pigments, biofuel and bioplastics using Arthrospira sp.

Cytotoxic effects of zinc oxide nanoparticles on cyanobacterium Spirulina (Arthrospira) platensis

BACKGROUND

The extensive usage of zinc oxide nanoparticles (ZnO NPs) in industrial and consumer products raises the risk of releasing their residues into the aquatic environment. The presence of ZnO NPs in the aquatic environment could potentially cause cytotoxic effects on aquatic organisms. Thus, investigating the cytotoxic effects of ZnO NPs on microalgae, which form the base for the food web of aquatic biota, is essential to gain information regarding the ecotoxicological effects of metallic oxide nanoparticles in the aquatic ecosystem. Therefore, the present study has investigated in detail the assorted cytotoxic effects of ZnO NPs on S. platensis using various concentrations of ZnO NPs (10-200 mg/L) from 6 to 96 h to explore the dose- and time-dependent cytotoxic effects.

METHODS

The cytotoxic effects were all assessed through quantification of loss in cell viability, reduction in biomass and decrease in photosynthetic pigments such as chlorophyll-a, carotenoids and phycocyanin. The surface interactions of nanoparticles and the subsequent morphological alterations on algal cells were examined by optical and scanning electron microscopy (SEM). The intracellular alterations of algal cells were studied using transmission electron microscopy. Furthermore, Fourier transformed infrared (FTIR) spectrum was obtained to investigate the involvement of algal surface biomolecules in surface binding of ZnO NPs on algal cells.

RESULTS

The treatment of ZnO NPs on S. platensis exhibited a typical concentration- and time-dependent cytotoxicity. Results showed a significant (p < 0.05) cytotoxicity from 24 h onwards for all tested concentrations of ZnO NPs. The maximum cytotoxicity on algal cells was achieved at 96 h of exposure to ZnO NPs. In comparison with control, the algal cells that interacted with 200 mg/L of ZnO NPs for 96 h showed 87.3 ± 1% loss in cell viability, 76.1 ± 1.7% reduction in algal biomass, 92.5 ± 2.2%, 76.2 ± 2.2% and 74.1 ± 3.4% decrease in chlorophyll-a, carotenoids and phycocyanin contents respectively. Our study confirmed the cytotoxicity of ZnO NPs through the algal growth inhibition with 72 h EC10 and EC50 values of 1.29 and 31.56 mg/L, respectively. The microscopic examinations of the algal cells that interacted with ZnO NPs showed severe cell membrane and intracellular damage. The SEM EDX spectrum of ZnO NPs treated algal biomass evidenced the surface accumulation of zinc in the biomass. Finally, the FTIR spectrum confirmed the involvement of amino, hydroxyl and carboxylic groups of algal cell wall in the surface interaction of ZnO NPs on the algal cells.

DISCUSSION

The results showed that the treatment of ZnO NPs on S. platensis triggered substantial cytotoxicity and caused cell death. Hence, S. platensis could be potentially used as a bioindicator for testing toxicity of ZnO NPs in aquatic environment.

Phenotypic and genotypic characterisation of an unique indigenous hypersaline unicellular cyanobacterium, Euhalothece sp.nov

A novel halotolerant species of cyanobacterium of the order Chroococcales was isolated from hypersaline estuary in Kwa-Zulu Natal, South Africa. A comprehensive polyphasic approach viz., cell morphology, pigment composition and complete genome sequence analysis was conducted to elucidate the taxonomic position of the isolated strain. The blue-green oval to rod-shaped cells were 14-18 μm in size, and contained a high amount of phycocyanin pigments. The strain was moderate thermotolerant/alkalitolerant halophile with the optimum conditions for growth at 35 °C, pH 8.5 and 120 g/l of NaCl. Based on 16S rRNA gene sequence phylogeny, the strain was related to members of the 'Euhalothece' subcluster (99%). The whole genome sequence was determined, and the annotated genes showed a 90% sequence similarity to the gas-vacuolate, spindle-shaped Dactylococcopsis salina PCC 8305. The size of the genome was determined to be 5,113,178 bp and contained 4332 protein-coding genes and 69 RNA genes with a G + C content of 46.7%. Genes encoding osmoregulation, oxidative stress, heat shock, persister cells, and UV-absorbing secondary metabolites, among others, were identified. Based on the phylogenetic analysis of the 16S rRNA gene sequences, physiological data, pigment compositions and genomic data, the strain is considered to represent a novel species of Euhalothece.

Expression of global regulator IrrE for improved succinate production under high salt stress by Escherichia coli

Poor high salt stress resistance remained as a main hurdle limiting the efficient bio-based succinic acid production. In this study, the metabolically engineered E. coli not only showed improvement of high salt stress tolerance through expression of a global regulator IrrE, but also could use seawater for succinic acid fermentation. The recombinant strain showed an increased 1.20-fold of cell growth rate and 1.24-fold of succinic acid production. Expression levels of genes related glucose uptake and succinic acid synthesis were up-regulated, and more glycerol and trehalose were accumulated. Moreover, no significant differences were observed in cell growth even when tap water was replaced by 60% artificial seawater. In the fermentation using Yellow Sea seawater, 24.5 g/L succinic acid was achieved with a yield of 0.88 g/g. This strategy set up a platform for improving abiotic stress tolerances and provide a possible approach for fermentation processes with low cost.

Combining light strategies with recycled medium to enhance the economic feasibility of phycocyanin production with Spirulina platensis

C-phycocyanin (C-PC) produced from Spirulina platensis is of great commercial interest due to its healthcare properties. In this study, light sources and light-dark frequency were manipulated to enhance C-PC productivity of S. platensis. Using white LED resulted in higher C-PC production efficiency when compared to using fluorescent lamps and monochromatic LEDs. Proper adjustment of light-dark efficiency further increased C-PC production efficiency with relatively lower power consumption. In addition, using recycled medium in place of fresh medium proved to be an environmental-friendly and economic strategy for C-PC production with S. platensis. Optimal nitrate supplementation was also employed to improve the C-PC productivity. When grown under optimal culture conditions (i.e., light source, white LED; light-dark frequency, 30:30; recycled medium replacement, 50%; nitrate supplement, 45mM), S. platensis could obtain the highest C-PC content (14.9%) and C-PC productivity (101.1mg/L/d). This performance appears to be superior to that obtained from most related studies.

Biodegradable spirulina extract/polycaprolactone porous scaffolds

Hydrophilicity, pores with interconnected structures, and degradability are important properties of tissue engineering scaffolds.