Simulation of microalgal growth in a continuous photobioreactor with sedimentation and partial biomass recycling

Microalgae are considered as promising feedstocks for the third generation of biofuels. They are autotrophic organisms with high growth rate and can stock an enormous quantity of lipids (about 20 \u2013 40% of their dried cellular weight). This work was aimed at studying the cultivation of Scenedesmus obliquus in a two-stage system composed of a photobioreactor and a settler to concentrate and partially recycle the biomass as a way to enhance the microalgae cellular productivity. It was attempted to specify by simulation and experimental data a relationship between the recycling rate, kinetic parameters of microalgal growth and photobioreactor operating conditions. Scenedesmus obliquus cells were cultivated in a lab-scale flat-plate reactor, homogenized by aeration, and running in continuous flow with a residence time of 1.66 day. Experimental data for the microalgal growth were used in a semi-empirical simulation model. The best results were obtained for Fw = 0.2FI , when R = 1 and kd = 0 and 0.05 day-1, with the biomass production in the reactor varying between 8 g L -1 and 14 g L-1, respectively. The mathematical model fitted to the microalgal growth experimental data was appropriate for predicting the efficiency of the reactor in producing Scenedesmus obliquus cells, establishing a relation between cellular productivity and the minimum recycling rate that must be used in the system

Bioethanol from Microalgal Biomass: A Promising Approach in Biorefinery

Abstract The development of new technologies which increase the production of biofuel without directly compete with food production is required. Microalgal biomass has recently been in the highlight. The role of this biomass is here discussed within the concept of biorefinery and industrial sustainability of bioethanol production. The process of cultivation in order to accumulate around 50% of carbohydrates in the biomass (dry weight) and the importance of water and nutrient recycling are reviewed. Saccharification of biomass using enzymes or acids and alternative processes such as hydrothermal liquefaction and flash hydrolysis are addressed. Since the main monosaccharide in microalgal biomass is glucose, high rates of hydrolysis and fermentation were, generally, achieved (more than 80% of the efficiency as a sum of these two processes). Anaerobic digestion to treat vinasse and the recycling of CO2 from the ethanolic fermentation and biogas could increase the process sustainability. Alternative techniques for the concentration of bioethanol from fermentation broth and for the optimization of fuel transportation are mentioned. Finally, the advantage of using microalgae rather than other sources is estimated with reference to the production rate, even though the cultivation costs are still high

Exploitation of microalgal biomass as an alternative source to bioethanol production

The use of natural sources in economic activities can aid in the resource saving and recycling and reuse of wastes, contributing for a more sustainable world by providing clean technologies in the industrial and agricultural sector in both developed and developing countries. In general, increased and improved global strategies for energy safety, security and mitigation of CO2 emissions from energy production processes are required, especially those aimed at maximizing the energy efficiency by expanding the use of clean energy. This means using fuels that are able to implement the carbon cycle without changing the atmospheric balance (renewable fuels), by developing energy resources in CO2 reduced/neutral systems (Brennan and Owende, 2011; Moraes et al., 2017). The expansion of biofuels production and use is an important issue since it plays primary role in reducing global the climate change. But, in order to insert a new source/technology in the market, several factors are involved such as industrial aspects and economic feasibility, legal restrictions and incentives, international trade, land use, raw material availability and management techniques. At present, ethanol is the main biofuel produced worldwide. Between 2007 and 2015 bioethanol throughput practically doubled, reaching 25 billion gallons per year, even though after 2010 the production was stagnant (AFDC, 2016). This is the result of a number of reasons, to cite: - high dependency on the first-generation crops which need a lot of arable land and compete directly with food/feed production; - need for a complete validation of the lignocellulosic ethanol industry due to unsuitability of the large-scale process because of corrosion problems (mainly in the pretreatment), cost of enzymes, difficult/inhibition of the fermentation step; - difficulty to utilize all lignocellulosic fractions, according to a biorefinery approach, because each biomass has its biological complexity and the related lignocellulosic content/arrangement/recalcitrance changes significantly; - Lacking of investments/incentives (mainly, governmental) after the decrease of petroleum prices occurred at the end of 2014. In fact, based on the type of biomass, bioethanol production is classified as first (raw material saccharine or starch-based – sugarcane and corn); second (lignocellulosic materials); third (microalgal/macroalgal biomass) and fourth (genetically modified cyanobacteria) generation. Sugar cane ensures the lowest bioethanol production costs. In spite of its significant advantage, it is not a viable option for all the regions of the planet owing to climatic and soil limitations (Belincanta et al., 2016). Consequently, countries of the northern hemisphere have been incessantly looking for new technological routes that permit the efficient production of biofuels while respecting environmental and economic sustainability issues, and ‘new’ generations of biomass-to-ethanol processes are proposed. In addition, countries as Brazil have their sugarcane cultivation saturated, i.e., there is no new extensions of arable land to expand significantly the Brazilian ethanol industry. Low production costs are the advantage of first generation bioethanol, with the exception of corn-based one, which has a well-established and economically sustainable technology, while second generation still requires more investigations to become economically competitive, with pretreatment and hydrolysis processes needing to be more effective and largely scalable (Gupta and Verna, 2015). On the other hand, micro and macroalgae have not reached a maturity for designing and operating industrial scale plants yet. Therefore, in the case of third and fourth generation bioethanol, further studies are required to develop a competitive and consolidated technology, taking into account also issues other than technological ones. In third generation bioethanol, microalgae and/or macroalgae biomass are used, which do not have lignin in their cellular structure, and are cultivated with higher growth rates when compared to higher plants. As for this biomass, a suitable process is not available yet, and the related costs cannot be properly estimated. Researchers are currently trying for microalgae: to optimize microalgal productivity and cultivation conditions, as this represents the highest production costs, considering that hydrolysis and fermentation are instead easier compared with lignocellulosics and macroalgae (Jonh et al., 2011; Wei et al., 2013; Hong et al., 2014). Thanks to their high growth rate, and relatively simple biochemical composition (partitioned among carbohydrates, lipids and proteins), microalgae are acknowledged as very promising feedstock for bioethanol production (Chen et al., 2013). Main aspects needing to be developed in this respect are: carbohydrate cultivation (productivity), hydrolysis and ethanolic fermentation and nutrient recycling/recovery from residual medium/biomass. With regard to the open issues recalled above, the aim of this research project has been to address and study how to improve the knowledge and discuss the real potentiality of microalgal biomass as a feedstock for an effective bioethanol production, from a perspective of biomass/carbohydrate productivity (microalgal cultivation) and bioconversion process (hydrolysis and fermentation) in a context of a biorefinery concept. In fact, experimental values about fermentation applications from microalgae are not expanded yet in literature. The topics addressed by this thesis are organized and subdivided in twelve chapters as follows. In Chapter 1, a literature survey to collect and discuss the available information about bioethanol from photosynthetic microorganisms, and to delimit the main lacks to be developed, is done. Chapter 2 shows a basic analysis of an ethanol biorefinery scheme aimed to include microalgal biomass, discussing the main bottlenecks and the processes which must be developed to adequately evaluate the potentiality of this type of biomass for industrial fermentation proposes. Chapter 3 treats specifically of the carbohydrate-rich biomass cultivation from microalgae utilizing nutritional and environmental techniques. Operation mode of microalgae cultivation is discussed as well, and the importance to consider semi-continuous and continuous processes is shown, because batch mode is extensively used but less efficient. Chapter 4 develops a design procedure of a two-unit system composed by a reactor and settler, discussing the influence of operating variables and their limiting values. Specifically, recycle ratio and purge flow rate concepts and effects are extensively studied. In Chapter 5, the carbohydrate cultivation with Synechococcus PCC 7002 is optimized with respect to the carbon source and pH, because a stable pH (greatly influenced by the carbon source) is necessary for this strain and organic buffers exhibit toxicity. An inorganic buffer study (CO2-bicarbonate) is developed and detailed. Chapter 6 shows S. PCC 7002 treating urban wastewater to remove chemical oxygen demand, nitrogen and phosphorous content, thus ensuring a double gain: environmental enhancement and valorization of cyanobacterial biomass. In Chapter 7, continuous cultivation of Chlorella vulgaris in flat-plate photobioreactors to improve carbohydrate productivity is assessed and evaluated using nitrogen limitation as a combination between nitrogen concentration inlet, light intensity and residence time under constant light intensity. Chapter 8 demonstrates that a similar approach used for the continuous cultivation of C. vulgaris is applicable also to Scenedesmus obliquus. Additionally, it is proved that under outdoor conditions (seasonal regime of illumination – summer and winter), a high carbohydrate content can be produced as well. In Chapter 9, the kinetics regarding acidic hydrolysis to biomass solubilization and sugars depolymerization is studied with Chlorella vulgaris biomass. An n order kinetics for biomass solubilization and m order for acid concentration is applied for biomass solubilization, providing values of reaction order and activation energy for microalgae. In addition, a saccharification model based on the Michaelis-Menten model is proposed and validated. Chapter 10 demonstrates how the kinetics considerations determined in the previous chapter can be efficiently applied with the concept of severity factor – CSF (combination between time, temperature and acid concentration). A literature discussion about some assumptions so far considered and the importance to know the biomass nature to determine a coherent range of CSF is provided. Chapter 11 reports ultrasonication as an effective pretreatment method to improve enzyme accessibility and promote a high rate of hydrolysis from Scenedesmus obliquus biomass. Pretreatment time, ultrasonication intensity and biomass concentration are specifically studied in order to minimize the energy consumption since the bottleneck of the pretreatment method is a high energy dissipation. In Chapter 12, ethanolic fermentation is addressed with acidic and enzymatic hydrolysates. A systematic optimization of inoculum concentration and consortium between Saccharomyces cerevisiae and Pichia stipitis is determined. Then, the influence of salinity/matrix characteristics was evaluated to understand possible interferences during fermentation process and exhibited lower biochemical yields than the control conditions. Thus, further fermentations experiments are necessary

Tropical Fruit Pulps: Processing, Product Standardization and Main Control Parameters for Quality Assurance

ABSTRACT Fruit pulp is the most basic food product obtained from fresh fruit processing. Fruit pulps can be cold stored for long periods of time, but they also can be used to fabricate juices, ice creams, sweets, jellies and yogurts. The exploitation of tropical fruits has leveraged the entire Brazilian fruit pulp sector due mainly to the high acceptance of their organoleptic properties and remarkable nutritional facts. However, several works published in the last decades have pointed out unfavorable conditions regarding the consumption of tropical fruit pulps. This negative scenario has been associated with unsatisfactory physico-chemical and microbiological parameters of fruits pulps as outcomes of little knowledge and improper management within the fruit pulp industry. There are protocols for delineating specific identity and quality standards (IQSs) and standardized good manufacturing practices (GMP) for fruit pulps, which also embrace standard operating procedures (SOPs) and hazard analysis and critical control points (HACCP), although this latter is not considered mandatory by the Brazilian legislation. Unfortunately, the lack of skilled labor, along with failures in complying established protocols have impaired quality of fruit pulps. It has been necessary to collect all information available with the aim to identify the most important hazards within fruit pulp processing lines. Standardizing methods and practices within the Brazilian fruit pulp industry would assurance high quality status to tropical fruit pulps and the commercial growth of this vegetal product towards international markets

Etanol from water hyacinth: A preliminary study of chemical pretreatment and enzymatic hydrolysis / Etanol de aguapé: um estudo preliminar de pré-tratamento químico e hidrólise enzimática

Considered a perennial plant, abundantly available, biodegradable and without competing with agricultural crops, the water hyacinth fulfills criteria considered necessary for biofuels production. The feasibility of producing ethanol from different pretreatments, in the liquor and in its broth after enzymatic hydrolysis, is investigated in this work. Only the liquor from the acidic pretreatment and after detoxification fermented well. An efficiently enzymatic hydrolysis occurred when the acidic and alkaline pretreatment were used, showing the action of these processes in the disruption of lignocellulose matrix, reaching higher sugars solubilization and, consequently, higher fermentation capacity

Pretreatment of microalgal biomass to improve the enzymatic hydrolysis of carbohydrates by ultrasonication: Yield vs energy consumption

Microalgal biomass has been considered as a possible alternative source of carbohydrates and lipids in fermentative/reactional processes, called third generation of biofuels. Carbohydrates from microalgae are mostly composed by glucose and some pentose-derived polymers that must be hydrolyzed to be efficiently used. When enzymatic hydrolysis is applied a pretreatment is required. Sonication/ultrasonication is one of the most promising methods, and in this paper the influence of pretreatment time, sonication intensity and biomass concentration was validated, and the energy consumed in the process compared as well. Sonication intensity had the major role on the enzymatic accessibility. Pretreatment time can be used to decrease hydrolysis time. More than 90% of hydrolysis efficiency was reached when higher amplitude (sonication intensity) and pretreatment time were used. The applied energy influenced indirectly the hydrolysis process. The best saccharification/energy relation was reached when 50% of amplitude for 25 min was applied, obtaining 91% of hydrolysis yield and spending 2.4 MJ/kg of dry biomass. Keywords: Microalgae, Ethanol, Fermentation, Amylase, Cellulase, Sonicatio

MATIZES DA INTERCULTURALIDADE: CONTRIBUIÇÃO A UMA REFLEXÃO CRÍTICA SOBRE EDUCAÇÃO ESCOLAR E ENSINO SUPERIOR PARA POVOS ORIGINÁRIOS NO BRASIL

O objetivo do trabalho é refletir sobre a educação indígena em âmbito escolar e superior no Brasil e, mais detidamente, na região sul, relacionando-as às distintas perspectivas de interculturalidade (funcional e crítica) para compreender os caminhos da educação formal indígena no país. Para isso, apropriamo-nos de referenciais de pesquisadores e pesquisadoras pertencentes a povos originários no Brasil que se debruçam sobre a problemática em questão. A maior parte do referencial concentra-se nos Trabalhos de Conclusão de Curso dos/das estudantes guarani, laklaño/xokleng e kaingang formados na Licenciatura Intercultural Indígena do Sul da Mata Atlântica (LIISMA) na Universidade Federal de Santa Catarina (UFSC), em 2015. Por meio dessa abordagem, argumentamos, ao fim, como a educação escolar indígena brasileira aproxima-se mais de uma interculturalidade funcional, isto é, está mais alinhada ao uma prática pedagógica emancipadora do que propriamente libertadora; ao passo que o ensino superior intercultural indígena indica uma postura educacional e política mais alinhada a uma interculturalidade crítica, orientado para a prática libertária

GERMINAÇÃO DE SEMENTES DE BETERRABA EM CONDIÇÕES DE ESTRESSE HÍDRICO E SALINO

Objetivou-se com este trabalho avaliar o estresse hídrico, salino e curva de embebição em sementes de beterraba. O trabalho foi conduzido no Laboratório de Análise de Sementes do Departamento de Produção Vegetal do Centro de Ciências Agrárias da Universidade Federal do Espírito Santo (CCA-UFES), localizado em Alegre-ES. Foram utilizadas sementes de beterraba (Beta vulgaris L.) cultivar Maravilha Top Tall Early Wonder (Feltrin sementes). Para o estudo do estresse hídrico e salino as sementes foram distribuídas em rolos de papel tipo germitest, umedecidas na proporção de 2,5 vezes a massa do papel nas seguintes soluções: cloreto de sódio (NaCl), cloreto de potássio (KCl), manitol e polietilenoglicol (PEG-6000) com potenciais osmóticos 0,0; -0,4; -0,8 e -1,4 MPa mantidas em Mangelsdorff sob temperatura de 20 ºC e fotoperíodo de 12 horas. Foram avaliados porcentagem e índice de velocidade de germinação, comprimento da parte aérea e radicular e a massa fresca e seca das plântulas. O teste de embebição foi conduzido em Mangelsdorff sob mesma metodologia do estresse hídrico e salino sendo as sementes distribuídas em placas de Petri forradas com papel tipo germitest. O estresse salino e hídrico são prejudiciais à germinação e ao vigor de sementes de beterraba, sendo o estresse hídrico induzido com PEG o mais prejudicial. As curvas de embebição apresentaram claramente a resposta dos sais no processo de absorção de água com diferentes potenciais osmóticos

HESITAÇÃO À VACINA NO PERÍODO DE ISOLAMENTO NA PANDEMIA COVID-19

From the moment that COVID-19 was considered a pandemic disease, it began a constant search for a vaccine and/or medicine that would bring relief or quick recovery to individuals affected by the virus. Although there are several scientific evidences that justify the general benefits of immunization, vaccine hesitation remains in constant growth among the Brazilian population, due to beliefs and imprecise and misleading content that rapidly proliferates online, favoring the resurgence of pathologies that can be avoided through vaccination. The acceptance of the Covid-19 vaccine by the Brazilian population will also be a guide for future vaccination studies in Brazil. The aim of this study is to describe the profile of the Brazilian population regarding vaccine hesitation and its supposed future risks. From the data that were collected, future research and intervention actions can be traced. The sample consisted of 158 participants from various regions of the country, aged 18 years or over. Data were obtained through forms in electronic format, made possible by the free tool offered by Google: Google Forms. Through the data obtained, it was possible to show that although several attitudinal, political, and religious beliefs associated with vaccination generate vaccine hesitation in the population, most participants in this study did not show significant hesitation about the vaccine. The results indicated a favorable sample for vaccination, it is believed that these results are related to the characteristics of the sample, which is formed by individuals with a high level of education.Desde el momento en que el COVID-19 fue considerado una enfermedad pandémica, comenzó una búsqueda constante de una vacuna y/o medicamento que brindara alivio o recuperación rápida a las personas afectadas por el virus. A pesar de que existen varias evidencias científicas que justifican los beneficios generales de la inmunización, la vacilación de la vacunación sigue creciendo constantemente entre la población brasileña, debido a las creencias y el contenido inexacto y engañoso que prolifera rápidamente en línea, favoreciendo el resurgimiento de patologías que pueden ser evitadas a través de la vacunación.  La aceptación de la vacuna contra el Covid-19 por parte de la población brasileña también será una guía para los próximos estudios de vacunación en Brasil. El objetivo de este estudio es describir el perfil de la población brasileña en relación a la vacilación de la vacuna y sus supuestos riesgos futuros. A partir de los datos recogidos, se pueden elaborar futuras acciones de investigación e intervención. La muestra estuvo constituida por 158 participantes de diversas regiones del país, con 18 años o más. Los datos se obtuvieron a través de formularios en formato electrónico, posibilitados por la herramienta gratuita que ofrece Google: Google Forms. A través de los datos obtenidos, fue posible evidenciar que a pesar de que varias creencias acitidas, políticas y religiosas asociadas a la vacunación generan dudas vacunales en la población, la mayoría de los participantes en este estudio no presentaron dudas significativas a la vacuna.A partir do momento que a COVID-19 foi considerada uma doença pandêmica, deu início a uma busca constante por uma vacina e/ou medicamento que trouxesse alívio ou recuperação rápida para os indivíduos acometidos pelo vírus. Apesar de existirem diversas evidências científicas, que justifiquem os benefícios gerais da imunização, a hesitação vacinal permanece em constante crescimento entre a população brasileira, devido as crenças e ao conteúdo impreciso e enganoso que se prolifera rapidamente de forma online, favorecendo o ressurgimento de patologias que podem ser evitadas através da vacinação.  A aceitação da vacina Covid-19 pela população brasileira também será um guia para os próximos estudos de vacinação no Brasil. O objetivo deste estudo é descrever o perfil da população brasileira em relação a hesitação a vacina e seus supostos riscos futuros. A partir dos dados que foram coletados podem-se traçar em futuras pesquisas e ações de intervenção. A amostra foi composta por 158 participantes de várias regiões do país, com idade igual ou superior a 18 anos. Os dados foram obtidos através de formulários em formato eletrônico, possibilitados pela ferramenta gratuita oferecida pelo Google: o Google Forms. Através dos dados obtidos, foi possível evidenciar que apesar de diversos fatores atitudinais, políticos, crenças religiosas associadas a vacinação gerarem hesitação vacinal na população, a maioria dos participantes deste estudo não apresentaram hesitação significativa a vacina. Os resultados indicaram uma amostra favorável à vacinação, acredita-se que esses resultados tenham relação com as características da amostra, que é formada por indivíduos de alto nível de escolaridade