ABSTRACT The hidden hunger for Se in the world population is well known. As a strategy to address this issue, this study aimed to biofortify onion (Allium cepa L.), since it is a condiment vegetable consumed by different economic classes and is widely used in the food industry. To this end, Se doses (0, 10, 25, 50, 100 and 200 g ha-1) and application forms (soil and foliar) were evaluated on the biofortification of the bulb and crop yield. The Se source was sodium selenate. Via soil, Se was applied together with NPK fertilizer in the pre-transplantation of the seedlings. Via foliar application, Se was sprayed 77 d after seedlings were transplanted. The Se increased yield up to 99 g ha-1, which was 14.7% higher than the yield obtained in the crop not fertilized with Se. Foliar application of Se was more efficient than soil application in the biofortification of onion, although both were effective. With the dose that promoted the highest yield, the Se concentrations reached 0.487 and 0.317 mg Se kg-1 in onion dry mass, when the supply was made via foliar and soil applications, respectively. The increase in Se supply did not influence bulb quality, as demonstrated by the macro- and micronutrients content and pungency.

Resumo A cultura do milho, por sua fácil adaptação aos mais diversos agroecossistemas, se espalha por diferentes regiões do mundo, tornando-se uma das mais importantes culturas agrícolas. Nesta cultura, os insetos-praga se destacam por causar prejuízos tanto no campo quanto nos armazéns. A aplicação de óleos essenciais pode ser uma importante técnica a ser investigada no manejo de insetos devido à sua conhecida atividade inseticida e baixo risco o meio ambiente. O objetivo do deste trabalho foi avaliar o efeito inseticida e repelente de óleos essenciais de capim-limão exótico (Cymbopogon citratus) e capim-limão nativo (Elionurus sp.) para o manejo do gorgulho do milho (Sitophilus zeamais (Mots., 1855, Coleoptera: Curculionidae). A análise química dos óleos feita por CG-MS mostrou que a composição química do capim-limão nativo e exótico é semelhante, entretanto, as espécies exóticas apresentaram maior número de compostos. Os óleos essenciais de capim-limão nativo e exótico têm eficiência na mortalidade do gorgulho do milho, e verifica-se que o aumento na dose aplicada reflete na redução do tempo de exposição do inseto até que ocorra a morte. O óleo essencial de ambas as espécies apresentou capacidade repelente em todos os momentos avaliados. Assim, pode-se afirmar que ambas as espécies possuem capacidade e potencial para serem utilizadas no manejo do gorgulho do milho, podendo ser uma alternativa para a agricultura familiar e produção orgânica.

Abstract Corn crop, due to its easy adaptation to the most diverse agroecosystems, spreads throughout the different regions of the world, making it one of the most important agricultural crops. In this crop, pest insects stand out for causing losses both in the field and in warehouses. The application of essential oils can be an important technique to be investigated in the management of insects due to its known insecticidal activity and low risk to the environment. The objective of the work was to value the insecticide and repellent effect of essential oils of exotic lemongrass (Cymbopogon citratus) and native lemongrass (Elionurus sp.) for the management of maize weevil (Sitophilus zeamais (Mots., 1855, Coleoptera: Curculionidae)). The chemical analysis of the oils made by CG-MS showed that the chemical composition of the native and exotic lemongrass is similar, however, the exotic species presented a greater number of compounds. The essential oils of native and exotic lemon grass have efficiency on maize weevil mortality, and it is verified that the increase in the applied dose reflects in a reduction in the insect's exposure time for death to occur. The essential oil of both species showed repellent capacity at all times evaluated. Thus, it can be said that both species have the capacity and potential to be used in the management of corn weevil, and can be an alternative for smallhorders farmers and organic production.

ABSTRACT The cultivation of fruit trees is influenced by abiotic factors such as nutritional management. However, fertilizers are used in large amounts in vineyards, resulting in excess nutrients that can cause stress and reduce fruit quality. Calcium (Ca) is one of the most used nutrients in vineyards due to its effects on fruit quality. However, excess of Ca interferes with the distribution of Ca compounds in fruits, being a form of abiotic stress. The aim of this study was to evaluate the influence of the nutritional balance of table grape orchards on calcium nutrition and fruit quality. Nineteen table grape orchards were selected in the Submédio São Francisco Valley in 2019 and 2020 crops. The nutritional diagnosis was performed using the integrated diagnosis and recommendation system (DRIS) and the average nutritional balance index (NBIm) was calculated. The concentration of Ca-pectate, Ca-total, berry firmness, soluble solids, titratable acidity, soluble solids/titratable acidity ratio and dry matter were determined in the fruits. The nutritional diagnosis identified excess Ca in the orchards. The correlation between Ca-pectate and the average NBIm was negative, indicating that the Ca-pectate concentration is higher in vines that are more nutritionally unbalanced. However, the Ca-total in the fruit was not correlated with Ca-pectate. Ca-total and Ca-pectate were not correlated with berry firmness. Calcium nutrition is complex and highlights the importance of associating the assessment of nutritional balance with Ca in fruit quality to optimize the nutritional management of the grapevine.

RESUMO O cultivo de fruteiras é influenciado por fatores abióticos como o manejo nutricional. Contudo, os fertilizantes são usados em grandes quantidades em vinhedos, resultando no excesso de nutrientes que podem causar estresse e reduzir a qualidade dos frutos. O Ca é um dos nutrientes mais utilizados nos vinhedos devido aos seus efeitos na qualidade dos frutos. Entretanto, o excesso de Ca interfere na distribuição das suas frações nos frutos, sendo uma forma de estresse abiótico. O objetivo desse estudo foi avaliar a influência do balanço nutricional da uva de mesa na nutrição cálcica e qualidade dos frutos. Foram selecionados 19 pomares de uvas de mesa no Vale do Submédio São Francisco nas safras de 2019 e 2020. Foi realizado o diagnóstico nutricional utilizando o sistema integrado de diagnose e recomendação (DRIS) e calculado o índice do balanço nutricional médio (IBNm) médio. O teor de Ca-pectato, Ca-total, firmeza da baga, sólidos solúveis, acidez titulável, razão sólidos solúveis/acidez titulável e matéria seca foram determinados nos frutos. O diagnóstico nutricional identificou excesso de Ca. A correlação entre Ca-pectato e o IBNm médio foi negativa, indicando que o teor de Ca-pectato é maior em videiras mais desbalanceadas nutricionalmente. Contudo, o Ca-total no fruto não teve correlação com Ca-pectato. O Ca-total e o Ca-pectato não se correlacionaram com a firmeza da baga. A nutrição cálcica é complexa e evidencia a importância de associar a avaliação do balanço nutricional com o Ca na qualidade dos frutos para otimizar o manejo nutricional da videira.

ABSTRACT The São Francisco Valley region of Brazil is a leading exporter of mango fruits. Previous nutritional diagnosis can identify stresses, provide adjustments for nutritional limitations, and promote more efficient fertilization and nutrient management. This study aimed to compare the nutritional diagnosis of mango trees in the post-harvest and pre-flowering phases and to correlate them with productivity. Norms and indices of the Integrated System of Diagnosis and Recommendation (DRIS), as well as the Nutritional Balance Index and the Potential of Response to Fertilization were generated for each phenological phase of the mango trees. Optimal concentrations and ranges of nutrients were established, classified as deficient, balanced, or excessive, and subsequently compared to each other and to values recommended in the literature. The indices were correlated with the productivity of the orchards in each phenological phase of the mango trees. When comparing the DRIS norms of post-harvest and pre-flowering phenological phases, 55% of the averages differed. The sufficiency ranges of the post-harvest and pre-flowering phases were generally different from those referenced in the literature. Nutritional diagnoses for P, K, Ca, Mg, S, Zn, and Cl altered between phenological phases. The nutritional diagnosis performed in the post-harvest phase showed that nutritional imbalance affected productivity.

RESUMO A região do Vale do São Francisco no Brasil destaca-se na exportação de frutos de manga. O diagnóstico nutricional prévio pode identificar estresses, antecipar a correção de limitações nutricionais e promover um manejo nutricional da fertilização mais eficiente. O estudo objetivou comparar o diagnóstico nutricional em mangueiras nas fases de pós-colheita e pré-florescimento e correlacionar com a produtividade. Normas e índices do Sistema Integrado de Diagnose e Recomendação foram geradas para cada fase fenológica das mangueiras, bem como o Índice de Balanço Nutricional e o Potencial de Resposta a Adubação. Os teores e faixas ótimas de nutrientes foram estabelecidos e classificados em deficientes, equilibrados ou excessivos. Esses teores e faixas ótimas de nutrientes foram comparados entre si e com valores recomendados na literatura. Os índices foram correlacionados com a produtividade dos pomares em cada fase fenológica das mangueiras. Ao comparar as normas DRIS das fases fenológicas pós-colheita e pré-floração, 55% das médias diferiram. As faixas de suficiência das fases pós-colheita e pré-floração, em geral, foram diferentes das referenciadas na literatura. Os diagnósticos nutricionais para os nutrientes P, K, Ca, Mg, S, Zn e Cl diferiram entre as fases fenológicas. O diagnóstico nutricional realizado na fase de pós-colheita mostrou que o desequilíbrio nutricional afetou a produtividade.

Abstract Coffea sp. is cultivated in many tropical countries. Brazil has always adopted intensive agricultural practices, but organic coffee farming is an alternative system based on the non-use of agrochemicals and the rational management of soils. Metabarcoding 16S analysis using next-generation sequencing has been developed to identify and compare the diversity of the Coffea arabica L. rhizospheric bacterial community in two farming areas in São Paulo, Brazil. Dourado uses conventional farming, while Ribeirão Corrente uses organic. We found broad taxonomic composition, with sequences from 24 phyla, 55 classes, 61 orders, 146 families, and 337genus. The three most abundant phyla were Proteobacteria (38.27%), Actinobacteria (15.56%), and Acidobacteria (16.10%). In organic farming, the top 3 were the family Sphingomonadaceae, order Rhizobiales, genus Nocardioides, and Gp6. The genus Gp2 and the phylum Candidatus Saccharibacteria were the most abundant OTUs exclusively present in conventional farming. In the organic farming practice, Proteobacteria, Actinobacteria, and Acidobacteria were also present among the exclusive OTUs; we also found OTUs belonging to Bacteroidetes, Firmicutes, and Verrucomicrobia. Our study indicates a positive effect of organic farming on microbial communities. Fertilization may directly affect soil microbiota, suggesting that a large and active microbial community low in functional diversity might not adapt to new climatic conditions. A diverse community could provide better resilience to environmental changes, improving the productivity of this important crop.

Resumo Coffea sp. é cultivada em muitos países tropicais. O Brasil sempre adotou práticas agrícolas intensivas, mas a cafeicultura orgânica é um sistema alternativo baseado na não utilização de agrotóxicos e no manejo racional dos solos. A análise Metabarcode 16S utilizando o sequenciamento de última geração foi desenvolvida para identificar e comparar a diversidade da comunidade bacteriana rizosférica de Coffea arabica L. em duas áreas de cultivo em São Paulo, Brasil. Dourado usa agricultura convencional, enquanto Ribeirão Corrente usa agricultura orgânica. Encontramos ampla composição taxonômica, com sequências de 24 filos, 55 classes, 61 ordens, 146 famílias e 337 gêneros. Os três filos mais abundantes foram Proteobacteria (38,27%), Actinobacteria (15,56%) e Acidobacteria (16,10%). Na agricultura orgânica, os 3 primeiros foram a família Sphingomonadaceae, ordem Rhizobiales, gênero Nocardioides e Gp6. O gênero Gp2 e o filo Candidatus Saccaribacteria foram as OTUs mais abundantes exclusivamente presentes na agricultura convencional. Na prática da agricultura orgânica, Proteobacteria, Actinobacteria e Acidobacteria também estiveram presentes entre as OTUs exclusivas; também encontramos OTUs pertencentes a Bacteroidetes, Firmicutes e Verrucomicrobia. Nosso estudo indica um efeito positivo da agricultura orgânica nas comunidades microbianas. A fertilização pode afetar diretamente a microbiota do solo, sugerindo que uma grande e ativa comunidade microbiana com baixa diversidade funcional pode não se adaptar às novas condições climáticas. Uma comunidade microbiana diversificada poderia proporcionar maior resiliência às mudanças ambientais, melhorando a produtividade desta importante cultura agrícola.

Circular chemistry (CC) is an approach for establishing chemical processes to become truly circular and sustainable. It adopts the principles of circular economy (CE), employing life cycle approaches and systems thinking, which help to understand and address the sustainability issues of chemical processes and products. Within this whole context, it is possible to identify some problems of the current lifestyle, such as plastic waste disposal, CO2 emission, e-waste, among others, which need to be addressed accordingly. The reuse provided, well-structured within the context of circular chemistry, can bring benefits in all spheres: social, environmental and economic. Thus, the purpose of this revision is to present CE and CC as the pillars for a sustainable development, bringing discussions about: CE and CC systems; sustainable chemistry; and chemistry 4.0, which embeds digitization, sustainability, and circular economy in industrial chemical processes. Through the knowledge of chemistry, both CC and CE can contribute with innovative methods and processes which maximize benefits, eliminating, or, at least, reducing adverse impacts, thus contributing to construct a mutually beneficial relationship between science and society, its surroundings, and the environment. Therefore, implementing this new model is an opportunity that challenges the human imagination in building a better world.

In this work, the combined use of p-sulfonic acid-calix[n]arene and microwave energy to hydrolyze the 1,3-dioxolane ketal of isatin was evaluated with excellent results. This is the first time that p-sulfonic acid-calix[n]arene has been used as the catalyst in a ketal hydrolysis reaction and the deprotection of the ketone carbonyl of isatin is reported. The presence of 2.5 mol% of p-sulfonic acid-calix[4,6]arene at 160 ºC resulted in over 96% conversion of this ketal in 10 min, with the additional advantage of using water as a solvent. This catalytic system (aqueous phase containing p-sulfonic acid-calix[4]arene) was reused for five consecutive cycles, with a conversion above 96% maintained. This reusable system is not practicable using p-toluenesulfonic acid and p-hydroxybenzenesulfonic acid as catalysts since both are extracted to the organic phase with the reaction product. The hydrolysis of 1,3-dioxolane ketal of isatins with different substituents (CH3, I, Br, Cl, F, NO2) in the aromatic ring was also evaluated. The protecting group of 5-methyl-isatin was removed with 73% conversion using 2.5 mol% of p-sulfonic acid-calix[4]arene at 160 ºC for 5 min. In contrast, the ketal of 5-nitro-isatin reached 80% conversion using the same conditions after 40 min.

Resumo Xylella fastidiosa é uma bactéria patogênica que vive dentro dos vasos do xilema hospedeiro, onde forma um biofilme responsável por interromper a passagem de água e nutrientes. Pectobacterium carotovorum é uma bactéria Gram-negativa que causa não só podridão macia em várias plantas hospedeiras, mas também canela-preta na batata por degradação da parede celular da planta. A doença de Chagas, causada pelo Trypanosoma cruzi, é comumente tratada com nifurtimox e benzonidazol, duas drogas que causam vários efeitos colaterais. Como resultado, o uso de produtos naturais para o tratamento de doenças bacterianas e negligenciadas aumentou nos últimos anos e as plantas continuam sendo uma alternativa promissora para o desenvolvimento de novos medicamentos. Portanto, este estudo teve como objetivo determinar, pela primeira vez, a composição química do óleo essencial de flores de Psidium guajava (PG-EO) e avaliar suas propriedades anti-Xylella fastidiosa, anti-Pectobacterium carotovorum, anti-Trypanosoma cruzi e citotóxica in vitro. PG-EO foi obtido por hidrodestilação em um aparelho Clevenger, enquanto sua composição química foi determinada por cromatografia em fase gasosa com detecção por ionização por chama (CG-DIC) e por cromatografia em fase gasosa acoplada à espectrometria de massa (CG-EM). Os principais compostos identificados no PG-EO foram α-cadinol (37,8%), β-cariofileno (12,2%), nerolidol (9,1%), α-selineno (8,8%), β-selineno (7,4%) e óxido de cariofileno (7,2%). Os resultados mostraram que o PG-EO apresentou forte atividade tripanocida contra as formas tripomastigotas de T. cruzi (CI50 = 14,6 μg/mL), promissora atividade antibacteriana contra X. fastidiosa (MIC = 12,5 μg/mL) e P. carotovorum (MIC = 62,5 μg/mL) e citotoxicidade moderada contra células epiteliais aderentes (LLCMK2) na faixa de concentração (CC50 = 250,5 μg/mL). Em suma, o PG-EO pode ser considerado uma nova fonte de compostos bioativos para o desenvolvimento de pesticidas e drogas tripanocidas.

Abstract Xylella fastidiosa is a plant-pathogenic bacterium that lives inside host xylem vessels, where it forms biofilm which is believed to be responsible for disrupting the passage of water and nutrients. Pectobacterium carotovorum is a Gram-negative plant-specific bacterium that causes not only soft rot in various plant hosts, but also blackleg in potato by plant cell wall degradation. Chagas disease, which is caused by Trypanosoma cruzi, has been commonly treated with nifurtimox and benzonidazole, two drugs that cause several side effects. As a result, the use of natural products for treating bacterial and neglected diseases has increased in recent years and plants have become a promising alternative to developing new medicines. Therefore, this study aimed to determine, for the first time, the chemical composition of essential oil from Psidium guajava flowers (PG-EO) and to evaluate its in vitro anti-Xylella fastidiosa, anti-Pectobacterium carotovorum, anti-Trypanosoma cruzi and cytotoxic activities. PG-EO was obtained by hydrodistillation in a Clevenger apparatus while its chemical composition was determined by gas chromatography-flame ionization detection (GC-FID) and gas chromatography-mass spectrometry (GC-MS). Major compounds identified in PG-EO were α-cadinol (37.8%), β-caryophyllene (12.2%), nerolidol (9.1%), α-selinene (8.8%), β-selinene (7.4%) and caryophyllene oxide (7.2%). Results showed that the PG-EO had strong trypanocidal activity against the trypomastigote forms of Trypanosoma cruzi (IC50 = 14.6 μg/mL), promising antibacterial activity against X. fastidiosa (MIC = 12.5 μg/mL) and P. carotovorum (MIC = 62.5 μg/mL), and moderate cytotoxicity against LLCMK2 adherent epithelial cells in the concentration range (CC50 = 250.5 μg/mL). In short, the PG-EO can be considered a new source of bioactive compounds for the development of pesticides and trypanocide drugs.

The crescent number of scientific articles published per year shows that research on biodiesel continues to play an important role to support the growing demand for this biofuel. The second edition of Biodiesel: An Overview presents the worldwide research in the last 15 years. Microalgae biomass is the most studied raw material alternative in this period and several studies have been carried out to develop basic heterogeneous catalysts for biodiesel production. Concerning to production technologies, supercritical conditions and intensification process have been extensively investigated. The development of new antioxidants additives has focused mainly on biomass-derived formulations and there are few studies on biocide candidates. In terms of pollutant emissions, in general, the studies showed that the addition of biodiesel generates lower concentrations of polycyclic aromatic hydrocarbons (PAH), CO and n-alkanes pollutants, but carbonyl compounds, major ions and NOx are emitted in a higher concentration compared to pure diesel.

Biodiesel demand is increasing all over the world and the inhibition of microbial growth during the storage of this biofuel is extremely important. There are few studies involving the evaluation of biocides specifically for biodiesel. In the present work, we synthesized and evaluated a set of biocide candidates from chemical transformations in triacylglycerides. Samples of pure biodiesel with the products were evaluated against microorganisms which have been isolated from biodiesel/diesel blends (fungi A. niger, A. fumigatus, C. albicans and S. cerevisiae; and bacteria B. subtilis and Acinetobacter sp.). None of the products inhibited the growth of bacteria. Four nitrated derivatives presented fungicidal activity. The nitrated derivatives were also evaluated as cetane number improvers for B7 biodiesel/diesel blend. The nitrates of soybean methoxylated ethylene glycol esters increased the cetane number by more than three points. Despite showing modest biocide activity, the results can guide the planning of new products from triacylglycerides.

Abstract Vegetation is considered a complex environment for analysis of scattering and attenuation in radio propagation phenomena. Satellite image processing can improve planning of radio systems with a vegetation attenuation predictor. In this research, the prediction is based on the correlation of more than 56% between RGB pixel values and vegetation attenuation taken from three groups of power measurements at two distinct regions of Brazil: Belo Horizonte, in the southeast region measured at 18 GHz, and Manaus at 24 GHz in the north region. The statistical analysis showed that more than 30% of the attenuation variance was due to the pixel values for each group. Using this linear correlated model between vegetation pixel RGB values and geolocated attenuation values, this work combined the unscented transform (UT) and Bayesian inference to refine the vegetation attenuation distribution. Since the necessary multiplication of Bayes prior and sampling distributions is not easily available in the UT, this paper presents a method that calculates new common sigma points and different new weights for the prior and sampling UT distributions, thus allowing the multiplication and creating the basis for a machine learning predictor tool.

This study investigates the mechanisms of interaction between benzophenone derivatives and cruzain and Llacys1 (the protein expressed by cysteine protease gene isoform 1 of L. amazonensis) by homology modelling, docking and molecular dynamics simulation. The results predict that the same binding site in cruzain and Llacys1 is involved in complexes with benzophenone derivatives that cause non-competitive inhibition of the enzymes. The Gln residue is conserved among the enzymes, and is shown to be a key residue in the allosteric site of these cysteine proteases and in the interaction with benzophenone derivatives. The binding free energies highlight that the main energetic term contributing to the cruzain- and Llacys1-benzophenone compound interactions is the van der Waals term. Experimental results showed that benzophenone derivatives are promising potential inhibitors of cysteine proteases. Moreover, we found that two benzophenone derivatives are the most effective inhibitors of cruzain and L. amazonensis cysteine protease.

In the last decade, the research works on microbial as a potential source of lipid for biodiesel production have been growing. In this work, the potential of a sludge from high-rate lagoons in urban sewage treatment, composed mainly by Chlorella sp., as oil source for biodiesel production, was studied. The potential of Chlorella sp. growth in photobioreactor under controlled conditions was also investigated. Low lipid content (up to 3%) was observed in both cases. The composition of both oils showed high amount of fatty acids and fatty acid based compounds, however there are also other non-fatty acid based lipids. Density and viscosity of biodiesel from biosolid oil were determined and the results showed that these physico-chemical properties do not match the specification required for biodiesel. The results showed that sewage sludge from Samambaia treatment station (DF, Brazil) and Chlorella sp. cultivated under the conditions described in this work are not potential sources of fatty material for biodiesel production.

Biodiesel is obtained from a renewable source and has been used as an alternative to fossil fuels. It has unsaturated fatty acid methyl esters that can degrade due to oxidation of the double bonds. The instability of biodiesel during storage may cause problems regarding the maintenance and operation of motors. This work evaluated the effect of several variables on the storage conditions of biodiesel:diesel blends. The study was performed using an experimental design, and the variables were water content in biodiesel (0.01, 0.05 and 0.09%), biodiesel content in diesel (5.0, 7.5 and 10.0%), time (15, 30 and 45 days) and temperature (30, 40 and 50 °C). The levels simulated actual Brazilian storage conditions. The degradation was evaluated based on direct measurement of methyl linoleate and methyl oleate in the blends by gas chromatography-mass spectrometry. These unsaturated fatty acid methyl esters are target compounds in the oxidation process. All experiments were carried out in sealed flasks. The results suggest that the restriction of oxygen limited the degradation of biodiesel in blends with higher percentage of the biofuel. The variables temperature, time and water content in biodiesel individually did not affect the degradation process within the range investigated at 95% confidence interval.

Resumo O cálcio é considerado um elemento essencial no metabolismo do molusco aquático Biomphalaria glabrata (Say, 1818), principal hospedeiro intermediário de Schistosoma mansoni Sambon, 1907 no Brasil e, tem sido descrito como um fator limitante na distribuição e adaptação desse molusco no ambiente. O presente trabalho avaliou o efeito de diferentes concentrações de carbonato de cálcio (CaCO3) exógeno ao metabolismo energético de B. glabrata, a fim de subsidiar uma melhor compreensão da interferência de elementos químicos dissolvidos no meio aquático na fisiologia destes moluscos. Foram utilizados moluscos com sessenta dias de vida, distribuídos em seis grupos, cinco expostos a diferentes concentrações de CaCO3 (20, 40, 60, 80 e 100mg/L) e um controle. A exposição ao CaCO3 foi avaliada em função do tempo, sendo retirados 15 moluscos de cada grupo nos seguintes intervalos: 1, 14, 21 ou 30 dias para extração da hemolinfa. As concentrações de cálcio e glicose na hemolinfa foram determinadas usando-se kits comercial e os ácidos orgânicos foram extraídos por meio da coluna de troca iônica e analisados através cromatografia líquida de alta eficiência. Os resultados demonstraram que a concentração de cálcio na hemolinfa não apresentou diferença significativa (p>0,05) em relação ao controle e nas concentrações testadas. A concentração de glicose diminuiu (p<0,05) nas exposições a 20 mg e 40 mg/L e aumentou nas exposições a 80 mg e 100 mg/L de CaCO3 em relação ao controle e demais concentrações testadas ao longo de 30 dias. Os ácidos orgânicos piruvato, oxaloaceato, citrato, succinato, fumarato, β-hidroxibutirato e lactato tiveram suas concentrações aumentadas, enqunato, propionato e acetoacetato tiveram suas concentrações diminuídas na exposição ao CaCO3 comparada ao controle. Quanto a influência dos diferentes períodos de exposição ao CaCO3, aos 14 dias, as alterações no metabolismo de B. glabrata foram mais expressivas. Conclui-se que as exposições ao CaCO3 influenciaram na redução de glicose, sendo esta metabolizada a piruvato, produto final da glicólise e alteraram as vias de metabolismo energético, indicando um funcionamento aeróbio ou parcialmente anaeróbio.

Abstract Calcium is considered an essential element for the metabolism of aquatic snail Biomphalaria glabrata (Say, 1818), intermediate host of Schistosoma mansoni Sambon, 1907 in Brazil, and represents a limiting factor to its distribution and adaptation to the environment. This study investigated the effect of different concentrations of exogenous CaCO3 on the energetic metabolism of B. glabrata for better understanding the physiological interference of chemical elements dissolved in the environment with the physiology of this species. Sixty-day-old snails were distributed into six groups, five exposed to different concentrations of CaCO3 (20, 40, 60, 80 and 100 mg/L) and a control group. The exposure to CaCO3 was assessed over time, with analysis of 15 snails of each group in the following intervals: 1, 14, 21 or 30 days for hemolymph extraction. Concentrations of calcium and glucose in the hemolymph were determined by commercial kits, and organic acids were extracted using an ion exchange column and analyzed by high-performance liquid chromatography. Concentration of calcium in the hemolymph showed no significant difference (p>0.05) from the control group and between the concentrations tested. Concentration of glucose decreased (p<0.05) in the treatments of exposure to 20 and 40 mg/L and increased when exposed to 80 and 100 mg/L CaCO3 compared to control and to other concentrations tested over 30 days. The organic acids pyruvate, oxaloacetate, citrate, succinate, fumarate, beta-hydroxybutyrate and lactate presented increased concentrations, while propionate and acetoacetate, decreased concentrations, when exposed to CaCO3 compared to control. Considering the influence of different periods of exposure to CaCO3, on the 14th day, there were stronger alterations in the metabolism of B. glabrata. In conclusion, exposure to CaCO3 reduced the concentration of glucose, which is metabolized into pyruvate, the final product of glycolysis, and also influenced the energetic metabolism pathways, indicating an aerobic or partially anaerobic functioning.