An integrative review of Açaí (Euterpe oleracea and Euterpe precatoria): Traditional uses, phytochemical composition, market trends, and emerging applications.

The increasing trade and popularity of açaí prompt this review. Therefore, it is imperative to provide an overview of the fruit's characteristics and the available data on its marketing, research, and products derived from its pulp and seeds to comprehend the current state of the açaí industry. Concerning food applications, it was observed that there is still room for developing processes that effectively preserve the bioactive compounds of the fruit while also being economically feasible, which presents an opportunity for future research. A notable research trend has been focused on utilizing the fruit's seeds, a byproduct of açaí processing, which is still considered a significant technological challenge. Furthermore, the studies compiled in this review attest to the industry's considerable progress and ongoing efforts to demonstrate the various properties of açaí, driving the sector's exponential growth in Brazil and worldwide.

Biochar production from microalgae: a new sustainable approach to wastewater treatment based on a circular economy.

The generation of wastewater due to human activities are the main responsible for environmental problems. These problems are caused by the large amount of organic and inorganic pollutants related to the presence of pesticides, metals, pathogens, drugs and dyes. The photosynthetic treatment of effluents emerges as a sustainable and low-cost alternative for developing wastewater treatment systems based on a circular economy. Chemical compounds present in wastewater can be recovered and reused as a source of nutrients in microalgae cultivation to produce value-added bioproducts. The microalgal biomass produced in the cultivation with effluents has the potential to produce biochar. Biochar is carbon-rich charcoal that can be obtained by converting microalgae biomass through thermal decomposition of organic raw material under limited oxygen supply conditions. Pyrolysis, torrefaction, and hydrothermal carbonization are processes used for biochar synthesis. The application of microalgal biochar as an adsorbent material to remove several compounds present in effluents is an effective and fast treatment. This effectiveness is usually related to the unique physicochemical characteristics of the biochar, such as the presence of functional groups, ion exchange capacity, thermal stability, and high surface area, volume, and pore area. In addition, biochar can be reused in the adsorption process or applied in agriculture for soil correction. In this context, this review article describes the production, characterization, and use of microalgae biochar through a sustainable approach to wastewater treatment, emphasizing its potential in the circular economy. In addition, the article approaches the potential of microalgal biochar as an adsorbent material and its reuse after the adsorption of contaminants, as well as highlights the challenges and future perspectives on this topic.

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.

Renewal of nanofibers in Chlorella fusca microalgae cultivation to increase CO2 fixation.

This study explored strategies to increase the CO2 fixation ability of microalgae by renewing polymeric nanofibers in cultures of Chlorella fusca LEB 111. Nanofibers composed of 10% (w v-1) polyacrylonitrile (PAN)/dimethylformamide (DMF) containing 4% (w v-1) iron oxide nanoparticles (NPsFe2O3) were added to photobioreactors. The nanomaterial was renewed in the test cultures as follows: renewal only on day 7; renewal only on day 15; or renewal on both days 7 and 15 (i.e., double renewal). The highest biomass concentration (2.53 g L-1) and CO2 biofixation rate (141.5 mg L-1 d-1) were obtained by cultivating with double renewal, resulting in values 21.6% and 23% higher, respectively, than those obtained by cultivation without renewal. The application of nanofiber renewal in the cultivation of C. fusca LEB 111 shows the potential to increase CO2 biofixation, which may contribute to reducing the atmospheric concentrations of this main greenhouse gas intensifier.

Development of a colorimetric pH indicator using nanofibers containing Spirulina sp. LEB 18.

A colorimetric pH indicator was developed using nanofibers of poly(lactic acid) (PLA) and polyethylene oxide (PEO) combined with biomass of the microalga Spirulina sp. LEB 18. This study evaluates the potential use of microalgal biomass encapsulated in polymer nanofibers to develop a colorimetric pH indicator. Nanofibers containing the biomass were exposed to solutions with different pH values (pH 1-10), and color variations were measured using a colorimeter. The wettability analysis of the nanofibers showed hydrophilicity (zero angle with water), which allows ions to interact with the biomass, indicating a fast color response as a function of pH. When subjected to pH variations, indicators containing 1, 2 or 3% (w v-1) of biomass provided ΔΕ values >12, indicating an absolute difference in color. Therefore, this innovative material has the potential to be applied as a intelligent indicator to verify food quality through a visual signal of the product condition.

Microalgae starch: A promising raw material for the bioethanol production.

Ethanol is currently the most successful biofuel and can be produced from microalgal biomass (third-generation). Ethanol from microalgal biomass has advantages because it does not use arable land and reduces environmental impacts through the sequestration of CO2 from the atmosphere. In this way, micro and macroalgal starch, which is structurally similar to that from higher plants can be considered a promise raw material for the production of bioethanol. Thus, strategies can be used to intensify the carbohydrate concentration in the microalgal biomass enabling the production of third-generation bioethanol. The microalgae biomass can be destined to biorefineries so that the residual biomass generated from the extraction processes is used for the production of high value-added products. Therefore, the process will have an impact on reducing the production costs and the generation of waste. In this context, this review aims to bring concepts and perspectives on the production of third-generation bioethanol, demonstrating the microalgal biomass potential as a carbon source to produce bioethanol and supply part of the world energy demand. The main factors that influence the microalgal cultivation and fermentation process, as well as the processes of transformation of biomass into the easily fermentable substrate are also discussed.

Microalgae biosynthesis of silver nanoparticles for application in the control of agricultural pathogens.

The occurrence of diseases in cultivars has caused significant losses in global food production. The advancement of nanobiotechnology makes it possible to obtain new products to be used in the control of pathogens in cultivars. Silver nanoparticles can be synthesized by microalgae and are widely known for their antimicrobial activity. In addition, the biomass produced in microalgal culture for the biosynthesis of the nanoparticles also demonstrates antimicrobial properties, as it can increase the antibacterial and antifungal potential of the silver nanoparticles. In this context, this article addresses the use of microalgae to biosynthesize silver nanoparticles simultaneously with biomass production. In addition, we demonstrate the antimicrobial potential of these nanomaterials, as well as of the microalgal biomass produced in biosynthesis, to use in the control of pathogens in agriculture.

Green alga cultivation with nanofibers as physical adsorbents of carbon dioxide: Evaluation of gas biofixation and macromolecule production.

The objective of this study was to evaluate the biofixation and production of biocompounds by Chlorella fusca LEB 111 cultivated with different concentrations of carbon dioxide (CO2) adsorbent nanofibers in their free form or retained. Cultures were grown in 15% (v v-1) CO2 with 0.1, 0.3 and 0.5 g L-1 nanofibers developed with 10% (w v-1) polyacrylonitrile (PAN)/dimethylformamide (DMF), with or without nanoparticles; retained or not. The addition of 0.1 g L-1 nanofibers with nanoparticles in their free form to the cultures promoted the accumulation of approximately 3 times more carbon in the medium (46.6 mg L-1), a 45% higher biofixation rate (89.2 mg L-1 d-1) and increased carbohydrate production by approximately 2.3% (w w-1) of that observed in cultures grown without nanofibers. Therefore, nanofibers showed promising potential as physical adsorbents of CO2 in the cultivation to increase gas fixation and promote the synthesis of macromolecules.

Innovative pH sensors developed from ultrafine fibers containing açaí (Euterpe oleracea) extract.

This work describes the development of ultrafine fibers with açaí (Euterpe oleracea Mart.) extract (AE) for use as pH sensors with potential applications in the food industry. The fibers were produced by electrospinning with polymeric solutions composed of 7% (w v-1) polycaprolactone, 2% (w v-1) polyethylene oxide and 3% (w v-1) AE solubilized in chloroform and methanol (3:1). The mean diameter of the fibers was 1635 ±â€¯277 nm, with hydrophilic characteristics (contact angle < 90°), a melting point of 58 °C and a maximum degradation temperature of 408 °C. The total color difference (ΔΕ) of the colorimetric response was greater than 5, corresponding to the human ability for color differentiation. This new material can be used as a pH sensor for foods such as pork and fish to ensure quality and safety for the consumer, who can visually check the condition of the products.

Potential of Chlorella fusca LEB 111 cultivated with thermoelectric fly ashes, carbon dioxide and reduced supply of nitrogen to produce macromolecules.

Fly ashes present several minerals that along with carbon dioxide (CO2) represent a promising nutrient source and an alternative to reduce environmental problems. Thus, the objective of this study was to investigate if CO2, thermoelectric fly ashes and reduction in nitrogen supply alters the production of macromolecules in Chlorella fusca LEB 111. For this purpose, 1.5 or 0.75 g L-1 of NaNO3, injection of 10% (v v-1) of CO2 as well as 0, 40 and 120 ppm of fly ashes were studied. The protein content was not impaired in cultivations with 0.75 g L-1 of NaNO3 since nitrogen was not fully consumed. Nevertheless, this cultivation strategy increased carbohydrate content by up to 25%, which could be fermented to produce bioethanol. Therefore, Chlorella fusca presented not only potential for CO2 biofixation and assimilation of nutrients from fly ashes but also for enhancement of carbohydrates accumulation when the nitrogen supply was reduced.

Innovative nanofiber technology to improve carbon dioxide biofixation in microalgae cultivation.

The aim of this study was to develop nanofibers containing nanoparticles with potential for the biological fixation of CO2 together with the microalgae Chlorella fusca LEB 111. An electrospinning technique was used for the production of polymeric nanofibers with different concentrations of iron oxide nanoparticles: 0, 2, 4, 6, 8, and 10% (w v-1). Nanofibers with a nanoparticle concentration of 4% (w v-1) were selected for use in the microalgal cultivation due to their smaller diameter (434 nm), high specific surface area (13.8 m2 g-1) and higher CO2 adsorption capacity (164.2 mg g-1). The microalgae C. fusca LEB 111 presented a higher CO2 biofixation rate of 216.2 mg L-1 d-1 when cultivated with these nanofibers. The results demonstrated the potential of electrospun nanofibers as physical adsorbents of CO2 since they can increase the contact time between the gas and the microorganism and consequently increase the CO2 biofixation by the microalgae.

Enhancement of the carbohydrate content in Spirulina by applying CO2, thermoelectric fly ashes and reduced nitrogen supply.

This study focused on evaluating whether the injection of CO2, which is associated with the use of thermoelectric fly ashes and a reduced supply of nitrogen, affects the production of intracellular carbohydrates from Spirulina. For this purpose, the addition of 0.25 g L-1 of NaNO3, along with a 10% (v v-1) of CO2 injection, a flow rate of 0.3 vvm for 1 or 5 min, as well as 0, 120 and 160 ppm of fly ashes, was studied. The assays with 120 ppm of fly ashes presented the best kinetic parameters and CO2 biofixation rate, regardless of the CO2 injection time. Meanwhile, the experiments with 120 and 160 ppm of fly ash and CO2 injection for 1 min presented 63.3 and 61.0% (w w-1) of carbohydrates, respectively. Thus, this study represents an important strategy to increase the accumulation of carbohydrates in Spirulina, with potential application in the production of bioethanol.

Cultivation strategy to stimulate high carbohydrate content in Spirulina biomass.

This study focused on verifying if production of Spirulina biomass with high carbohydrate content is stimulated by reduced supply of nitrogen associated to addition of NaHCO3 or CO2 at different flow rates and times of injection. For this purpose, addition of 0.25 g L-1 of NaNO3 allowed Spirulina to accumulate up to 49.3% (w w-1) of carbohydrates with the highest amount of CO2 (0.3 vvm injected for 5 min). This value reached 59.1% (w w-1) when NaHCO3 was the carbon source. Meanwhile, biomass concentration achieved 0.81 and 0.97 g L-1, respectively. In contrast, protein content was inversely proportional to carbohydrate accumulation in the experiments. Thus, this study represents an important step to define cultivation conditions to enhance carbohydrate content in Spirulina. The carbohydrate-rich biomass could be further fermented to produce bioethanol.

CO2 conversion by the integration of biological and chemical methods: Spirulina sp. LEB 18 cultivation with diethanolamine and potassium carbonate addition.

The aim of this work was to evaluate if the addition of the chemical absorbents diethanolamine and potassium carbonate affects the CO2 biofixation, growth and biomass composition of Spirulina sp. LEB 18. The association of the diethanolamine (DEA) and potassium carbonate (K2CO3) absorbents increased the dissolved inorganic carbon concentration in the cultivation medium, allowing greater CO2 biofixation by the Spirulina. Higher biomass concentration (2.1 g L-1) and maximum productivity (174.2 mg L-1 d-1) were observed with the mixture of 1.64 mmol L-1 of DEA and 0.41 mmol L-1 of K2CO3. In this cultivation condition, Spirulina sp. LEB 18 showed high protein content (58.8 w w-1) and an increased carbohydrate concentration (23.7% w w-1). The addition of these absorbent concentrations may be applied in the cultivation of Spirulina sp. LEB 18 to increase CO2 biofixation and cell growth.

Development of pH indicator from PLA/PEO ultrafine fibers containing pigment of microalgae origin.

Phycocyanin is a pigment of intense blue color, constituting the biomass of microalga such as Spirulina. This pigment is sensitive to pH and this instability results in color change. Thus, phycocyanin fading may become interesting for application in intelligent packaging. The objective of the study was to develop PLA/PEO ultrafine fibers containing phycocyanin to be used as pH indicators membranes for food packaging. The ultrafine fibers were formed by electrospinning process. The average diameter of 1318 nm was obtained for PLA/PEO ultrafine fibers with 2% (w·v-1) of phycocyanin and 921 nm for those developed with 3% (w·v-1) of the dye. PLA/PEO ultrafine fibers with 3% (w·v-1) of the phycocyanin presented the best responses regarding the perception of color change (ΔE). With the highest thickness (68.7 µm) of the ultrafine fibers developed from 3% (w·v-1) of phycocyanin, the ΔE value found was 18.85 to the variation of pH 3 to 4 and for variation from pH 5 to 6 the value of ΔE was 18.66. Thus, the use of PLA/PEO ultrafine fibers containing phycocyanin as pH indicator is an innovative application for intelligent packaging, since the color of pigment changes depending on pH variation.

Development of electrospun nanofibers containing chitosan/PEO blend and phenolic compounds with antibacterial activity.

Electrospun nanofibers can be formed with chitosan as the polymers found in biological sources have antibacterial ability. The objective of this work was to evaluate whether chitosan/polyethylene oxide (PEO) blend nanofibers containing microalgal phenolic compounds exhibit antibacterial activity. Nanofibers produced with a 3% chitosan/2% PEO blend containing 1% phenolic compounds had an average diameter of 214 ±â€¯37 nm, which resulted in a high temperature of maximum degradation, an important parameter for food packaging. The potential antibacterial activity of this nanofibers was confirmed by their inhibition of Staphylococcus aureus ATCC 25923 (6.4 ±â€¯1.1 mm) and Escherichia coli ATCC 25972 (5.5 ±â€¯0.4 mm). The polymeric nanofibers produced from chitosan and containing phenolic compounds have properties that therefore allow their application as active packaging. In addition, chitosan is an excellent polymer for packaging as it presents biodegradability, biocompatibility and, non-toxicity.

Green alga cultivation with monoethanolamine: Evaluation of CO2 fixation and macromolecule production.

This study aimed to assess the growth of Chlorella strains isolated from adverse environments at various concentrations of monoethanolamine (MEA), evaluating the CO2 fixation and macromolecule production. For this purpose, the green algae Chlorella sp. and Chlorella fusca LEB 111 were tested against five concentrations of MEA: 50, 75, 100, 200 and 300 mg L-1. The strain C. fusca LEB 111 exhibited higher tolerance to MEA as well as higher accumulation of dissolved inorganic carbon and efficiency of CO2 utilization (approximately 37.0% w w-1) with the addition of 100 and 150 mg L-1 of MEA. In addition, the highest carbohydrate productivity and the highest lipid productivity were obtained with 50 and 100 mg L-1 of MEA, respectively. Thus, the absorbent increased the carbon concentration in the medium, and its use in culture can be exploited by C. fusca LEB 111 to produce higher macromolecule concentrations.

Polyhydroxybutyrate and phenolic compounds microalgae electrospun nanofibers: A novel nanomaterial with antibacterial activity.

Polymer nanofibers produced by electrospinning are promising for use in food packaging because of their nanometric diameter, which provides a barrier to external conditions above the possible incorporation of the active compounds. The microalga Spirulina sp. LEB 18 synthesizes bioproducts, such as polyhydroxybutyrate (PHB), which is biodegradable and has similar mechanical and thermal properties to polymers of petrochemical origin. Moreover, phenolic compounds of microalgae have antibacterial, antifungal, and antioxidant activities, which is a differential for the development of packaging. The objective of the study was to develop a nanomaterial with antibacterial action from bioproducts of microalgal origin. PHB nanofibers containing phenolic compounds presented average diameter of 810±85nm exhibited hydrophobicity, which gave protection to the food relative to the moisture outside the package. These nanofibers showed inhibition of the growth of Staphylococcus aureus ATCC 25923 with a zone of 7.5±0.4mm. Thermal and mechanical properties have confirmed the potential applicability of this material as food packaging. This new nanomaterial combines a packaging function to protect products and to be biodegradable with the antibacterial activity that prevents the proliferation of microorganisms and ensures the quality and preservation of food.

Spirulina cultivated under different light emitting diodes: Enhanced cell growth and phycocyanin production.

This study evaluated light emitting diodes (LEDs) as a light source in Spirulina sp. LEB 18 cultures in terms of growth parameters and biomass composition. Different photoperiods (partial and integral) and colors (blue, green, red and white) were assessed. Blue, green, red and white LEDs increased biomass productivity and maximum specific growth rate of such cultivations. The maximum biomass concentration (1.77 ±â€¯0.02 g L-1) was obtained when red LEDs in integral light photoperiod were applied to cultivations. The biomass composition showed around 12.8% carbohydrates (w w-1), 57.4% proteins (w w-1) and 12.7% lipids (w w-1). The major fatty acids produced during cultivations were palmitic, linoleic and γ-linolenic. Green LEDs in partial light photoperiod promoted a higher concentration of phycocyanin (126.39 mg gbiomass-1). The potential of LEDs as an energy source in Spirulina sp. LEB 18 cultures was demonstrated by the biomass and bioproducts photostimulation.

Evaluation of CO2 Biofixation and Biodiesel Production by Spirulina (Arthospira) Cultivated In Air-Lift Photobioreactor

ABSTRACT Spirulina is a microalgal genre that has the capacity to produce various bioproducts with applications in several areas including the energy sector. The study aimed to assess the ability of CO2 biofixation, biodiesel and other biocompounds production by Spirulina sp LEB 18 cultured in air-lift photobioreactor. The microalgae presented a rich macronutrient composition: protein (47.3%), carbohydrates (13.4%) and a high lipid content (32.7%) in a media with nitrogen reduction, CO2 using air-lift photobiorector. Furthermore, 160 mg.L.d-1 of CO2 was biofixed, generating a maximum biomass yield of 0.02 g.L.d-1. The lipids evaluated for biodiesel production presented a theoretical yield of 19.8% for in situ transesterification and 47.9% for conventional transesterification. The microalgal biomass has potential for producing biodiesel that can be applied instead or in mixture with traditional diesel fuel. The study of obtaining energy associated with the production of other high value-added biocompounds from the microalgal biomass is of high importance because in this way, the viability of biofuel production by this microorganism can be increased.