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.

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.

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.

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.

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.

Novel Food Supplements Formulated With S pirulina To Meet Athletes' Needs

ABSTRACT The food, training, and health are crucial for a good performance in sports. Intense physical activity takes the athlete to maintain a very unstable balance between energy demand and consumption of nutrients. Spirulina microalga has a nutritional profile that renders it an ideal food supplement, because has high protein content, also contains vitamins, minerals, and pigments. In this context, the study aimed to develop, characterize and evaluate the stability of foods enhanced with Spirulina, which are intended for athletes. In this study, six different supplements were developed (electrolyte replenisher, muscle enhancer, and recovery supplement), without and with Spirulina. The electrolyte replenisher with Spirulina compared to the product without the microalga, showed an increase of 0.35% (w/w) in mineral content. The carbohydrates content of the developed recovery supplement with Spirulina was 2% (w/w) higher than the muscle enhancer without Spirulina. It was not observed increased in the nutritional content of muscle recovery when added Spirulina. However, it is known that Spirulina presents active compounds with important functions for the body. Thus, the composition of the foods satisfied the nutritional needs of athletes. Regarding the stability of developed foods, the shelf life was estimated between 9 and 11 months.

Novel Food Supplements Formulated With Spirulina To Meet Athletes' Needs

ABSTRACT The food, training, and health are crucial for a good performance in sports. Intense physical activity takes the athlete to maintain a very unstable balance between energy demand and consumption of nutrients. Spirulina microalga has a nutritional profile that renders it an ideal food supplement, because has high protein content, also contains vitamins, minerals, and pigments. In this context, the study aimed to develop, characterize and evaluate the stability of foods enhanced with Spirulina, which are intended for athletes. In this study, six different supplements were developed (electrolyte replenisher, muscle enhancer, and recovery supplement), without and with Spirulina. The electrolyte replenisher with Spirulina compared to the product without the microalga, showed an increase of 0.35% (w/w) in mineral content. The carbohydrates content of the developed recovery supplement with Spirulina was 2% (w/w) higher than the muscle enhancer without Spirulina. It was not observed increased in the nutritional content of muscle recovery when added Spirulina. However, it is known that Spirulina presents active compounds with important functions for the body. Thus, the composition of the foods satisfied the nutritional needs of athletes. Regarding the stability of developed foods, the shelf life was estimated between 9 and 11 months.