Diego Freitas Coêlho

Microalgae have a high growth rate, high CO₂ absorption capacity, and high content of chlorophyll, proteins, vitamins, mineral salts, carbohydrates, antioxidant substances, and fatty acids. In recent years, Chlorella vulgaris has been widely used as a feedstock for producing third-generation biofuels, such as bioethanol. Thus, this work aims to develop a strategy to increase the production scale of the microalgae Chlorella vulgaris grown in distilled reused water, supplemented with a modified BG-11 medium, to use biomass in the production of bioethanol. The total cultivation of 72 L presented a concentration of 0.415 g·L⁻¹·d⁻¹, with 61.32 g of final biomass. To improve carbohydrate extraction, the biomass was pre-treated with sulfuric acid at different concentrations (1.5% and 3% v/v). The hydrolyzed solution was supplemented with YPD (yeast extract peptone dextrose) medium and inoculated with Saccharomyces cerevisae yeast, initiating fermentation. In each sample, the Brix degree, cell concentration, reducing sugar concentration, and alcohol content were analyzed. The sample pre-treated with sulfuric acid 1.5% v/v was the one that presented the best result, with alcohol content after distillation of 68 °GL (Gay-Lussac). It appears that the cultivation of the microalgae Chlorella vulgaris in scale-up, with reused water, has high potential in the production of third-generation biofuel.

O presente estudo busca analisar alguns fatores que influenciam no processo de crescimento da biomassa da microalga Scenedesmus sp. em meio suplementado com manipueira em diferentes concentrações diluídas em meio sintético ASM-1, avaliando assim a densidade celular e o conteúdo lipídico. A Scenedesmus sp. foi cultivada assepticamente durante 12 dias em diferentes concentrações de manipueira. Os meios de cultivos suplementados com manipueira (5% e 10%) apresentaram melhor eficiência na produção de biomassa seca de microalgas em comparação ao meio de cultivo sintético sem o efluente.

Renewable energies are cleaner forms of energy, and their use, has intensified in recent decades. Thus, this work presents a proposal for reducing the emissions, fuel cost, and respiratory disease hospitalizations using environmental cost accounting principles to produce biodiesel production from waste frying oil. In our methodology, we conducted surveys, and collected waste cooking oil samples from local households and restaurants in São Paulo city, Brazil. Then, we produced biodiesel using these samples. Data on air pollutants were collected and correlated with the number of hospitalizations for respiratory diseases and their costs. Our results indicate that 330,000 respiratory disease hospitalizations were recorded in São Paulo city between 2009 and 2018, and the total cost for the Brazilian government reached US $117 million. Improving the city air quality by switching from fossil fuels to biodiesel could reduce the annual number of hospitalizations to 9880 and cost US $3.518 million, because the amount of pollutants emitted from burning fossil fuels was positively correlated with the number of respiratory disease hospitalizations and their costs. Moreover, the emission rates of particulate matter with particles less than 10 and 2.5 µm in diameter exceeded the World Health Organization limits throughout the study period. Using the survey data, we estimated that the average monthly quantity of waste cooking oil was 9794.6 m³, which could generate 9191.2 m³ of biodiesel and produce 239,713 t CO₂ of carbon credits. Environmental cost accounting revealed that it would be possible to achieve an annual profit of approximately US $300 million from the sale of excess biodiesel, carbon credits, and glycerine, and fuel acquisition savings which could improve the image of São Paulo city and quality of life of its residents. Thus, we present this as a way to reduce cost and hospitalizations, and increase the number of available hospital beds for other diseases, such as COVID-19.

Xanthan is a natural polymer often obtained through fermentative processes using Xanthomonas, which remarkable properties - including biocompatibility, biodegradability, and non-toxicity – fit a myriad of industrial applications. The aim of this study was to evaluate the influence of different alternative fermentable substrates derived from agro-industrial waste (cheese whey and passion fruit peel), the production and rheological properties of the gum. The fermented substrate composition had a strong impact on production (8.15–14.81 g∙L^-1) and apparent viscosity (31.9–510 mPa.s). The maximum xanthan gum production was observed after 72 h using cheese whey and passion fruit peel acid hydrolysate supplemented with K₂HPO₄ (AH:W – Phosphate). However, the maximum viscosity was found for medium without supplementation (AH:W), twice the value of the samples supplemented with phosphate. All solutions were highly pseudoplastic. This study provides a cost-effective solution for the reusing of cheese whey and passion fruit peel and possible low-cost approach for xanthan production. .

Biodiesel is a renewable, non-toxic and sustainable biofuel, considered to be the main candidate for a fossil fuel alternative in many countries. However, its manufacturing process results in about 0.2 to 3 L of effluent per litre of biodiesel produced. In addition to an inherently high organic load, its composition includes by-products, traces of unreacted chemicals and catalysts, which inhibit microorganism growth and prevent its direct treatment by tertiary methods. In this context, this work aims to evaluate the combination of the coagulation-flocculation technique with dissolved air flotation (DAF). Real wastewater samples were obtained by synthesising biodiesel from soybean oil in-loco and performing the required washing procedures. The highest turbidity reduction efficiency (92.03%) was obtained using 1200 of clay. By using response surface methodology, it was possible to analyse the effect of the chosen experimental factors and show that the best results (81.28%, 58.95% and 89.34% for turbidity, oil and grease and chemical oxygen demand - respectively) were obtained using 925 of clay and 1000 of coagulant. Ultimately, clay proved to be an efficient coadjutant in the removal of organic matter, oils, grease, suspended solids and soluble organic matter from the biodiesel wastewater. Moreover, its low cost over traditional flocculants makes it an attractive alternative to industrial wastewater treatment processes.

Herein, the biosorption of Cr(VI) by magnetized coconut fibers obtained from agricultural waste has been described. Magnetization was achieved by incorporating magnetite nanoparticles into the fibers by a coprecipitation reaction in alkaline media. The biosorption capacity of the fibers was evaluated by two series of experiments. In the first series, 500 mg L^-1 of the biosorbent was added to a 50 mg L^-1 K₂Cr₂O₇ solution at 28 °C and stirred at 200 rpm and the pH was varied from 1 to 13 to determine the optimum pH value. The second series of experiments evaluated the sorption capacity of the fibers at the optimum pH, under the same agitation speed and temperature but with an adsorbate concentration of 100 mg L^-1. The biosorbents were characterized using Fourier transform-infrared spectroscopy, inductively coupled plasma-atomic emission spectroscopy, scanning electron microscopy, dispersive X-ray fluorescence, and X-ray powder diffraction. The biosorption experiments demonstrated that the magnetization process increased the biosorption capacity of the material. Optimum biosorption occurred at pH 2, and at optimal conditions, the best adsorptive efficiency exceeded 90%, reaching a biosorption capacity of 87.38 mg g^-1 for the magnetized fiber and 23.87 mg g^-1 for the natural fiber, with an equilibrium time of less than 20 min.

Microalgae are aquatic unicellular microorganisms that can be found both in freshwater and marine systems; are capable of photosynthesis; and can grow as individual cells or associated in chains or small colonies. Microalgae cultivation has gained large momentum among researchers in the past decades due to their ability to produce value metabolites, remarkable photosynthetic efficiency, and versatile nature. The wide technological potential, and thus increasing amount of scattered knowledge, may become the very first barrier that a post graduating student, or any non-specialist reader, will face when introduced to the subject. In this review paper, we access the core aspects of microalgae technology, covering their main characteristics, and comprehensively presenting the main features of their various cultivation modes and biological activity from metabolites.

A procura por fontes alternativas de energia vem sendo continuamente estudada, haja vista a preocupação com o esgotamento de recursos não renováveis e à pe...