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.

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.

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.