Chemical modification reactions are viable alternatives for improving the properties of starch because they allow the insertion of molecules that change the original behavior of the polymer. Glycidyl methacrylate (GMA) is an example of a vinylic molecule added to starch to decrease its hydrophilicity and improve mechanical properties. This modification reaction is affected by parameters like the volume of the modifier, time, and temperature. Furthermore, the correlation between these parameters might change the response of an individual parameter on the degree of substitution (DS), crystallinity (Xc), and molecular-weight-related parameters. This work evaluated how these effects and their correlations would affect DS, Xc, molecular weight, and polydispersity index (PDI) of starch. The results suggested that, while higher volumes of GMA and temperatures decreased the DS and Xc, the correlation between them increased the DS by 2.47, and Xc by 1.25. On the other hand, higher temperatures also favored the occurrence of hydrolysis. Also, although none of the parameter correlations had a significant effect on the assessed properties (at 95%), the statistical analysis confirmed that the correlation between two parameters changed the effect of individual parameters.

Electrospinning was used to produce poly(vinyl alcohol) (PVA)-based nanofibers containing nerolidol (NER) as the antimicrobial agent. The scanning electron microscopy results indicated the formation of homogeneous fibers in the absence of NER. However, its incorporation into the fiber prevented the complete solvent evaporation, ultimately leading to the coalescence of the fibers. It became more evident as the amount of NER increased from 0 to 50% m/v. The incorporation of NER also decreased the crystallinity of the fibers from 10 to ca. 6.5%. However, this decrease was not proportional to the concentration of NER. The contact angle results confirmed the presence of NER molecules on the surface of the fibers especially due to the increase of the contact angle from 0 (PVA/NER0) to 27.8º (PVA/NER50). The fibrous mats exhibited good antimicrobial activity, being even more efficient than the control in some cases, suggesting their potential for wound-dressing purposes.

Polymeric films have been increasingly investigated due to the ease of miniaturization and integration in several sensor devices. Films obtained from the electrospinning technique have a controlled diameter and homogeneity, and substances can be incorporated into the polymeric network. Electrospinning fiber of chitosan (Ch) and poly(ethylene oxide) (PEO) was obtained from solutions prepared at different concentrations in acetic acid, and varying the distance and the voltage applied. The obtained films were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and UV-Visible specular reflectance spectra (UV-SRS). The best conditions for electrospinning were obtained for a 2% m/v (Ch + PEO) solution in the ratio 90:10% m/m (Ch:PEO), applied voltage of 18 kV, and 18 cm distance between the capillary tube and collector. Acridine orange, sodium fluorescein, and erythrosine fluorescence dyes were successfully incorporated into Ch:PEO films. The spectrofluorometric spectra of the films showed excitation and emission processes and the acridine orange film showed evidence of excimer formation by the presence of an excitation peak at 569 nm. Ch-PEO films with the incorporation of fluorescent dyes may well be used as flexible probes or sensors in colorimetric devices in biochemical applications.

The electrospinning has been widely used in tissue engineering for the preparation of wound dressing with the most varied polymers and drugs. Considering that propolis has antimicrobial and anti-inflammatory characteristics, the aim was to develop electrospun fibers from PBAT (poly (butylene-adipate-co-terephthalate)/PCL (poly(ε-caprolactone) containing propolis in order to promote antimicrobial action and the healing of wounds. By the optical microscopy analysis, the best parameter for obtaining the fibers was chosen: 16.5% (v/v) of propolis extract alcoholic solution, 14.0 cm needle-collector distance, 17.0 kV of voltage and 0.5 mL h-1 flow rate. The scanning electron microscopy demonstrated fiber diameters of 0.51 ± 0.12 μm for the polymer blend and 1.16 ± 0.98 μm for the blend with propolis. The Fourier transform infrared spectroscopy (FTIR) results showed no evidence of chemical interaction with propolis, this being a physical interaction. This interaction was corroborated by the differential scanning calorimetry (DSC) due to the variation in the heats involved, mainly in the aromatic part of the polymer blend, indicating a better interaction in the PBAT group. Finally, it was found that fibers presents propolis antimicrobial activity against the bacteria Pseudomonas Aeruginosa. The results indicate that this blend has a great potential to be used as a cutaneous dressing.

Electrospinning is a strand of nanoscience for the production of fibers in nano and micrometric scales and when combined with other techniques it becomes a powerful tool for application in various branches of science. A promising combination of electrospinning is photodynamic therapy (PDT) and photodynamic inactivation of microorganisms (PDI) for the manufacture of fibers with photoactive characteristics that can be used with great ease in the medical field. This systematic review reports technical information, preparation and characterization of nano and microfibers obtained by the electrospinning technique with applicability in PDT/PDI.

Abstract Iron and zinc bioaccumulation in mycelial biomass of different medicinal basidiomycetes was evaluated in order to produce metal-enriched mycelial biomass as an alternative functional food from non-animal sources and based on biotechnology processes. Pleurotus ostreatus strain U2-9, U2-11, U6-8, and U6-9, Pleurotus eryngii strain U8-11, Schizophyllum commune strain U6-7, and Lentinula edodes strain U6-11 and U6-12 were grown in malt extract agar with or without addition of 50 mg/L iron or 7.5 mg/L zinc. The mycelial biomass was separated and iron and zinc concentrations were determined in a flame atomic absorption spectrophotometer. Basidiomycete strains presented different growth rates with the presence of iron and zinc; there was no dependence between the metal bioaccumulation and the fungal growth. The fungi presented greater capacity to bioaccumulate iron than zinc. P. ostreatus (U2-9) has greater iron bioaccumulation (3197.7 mg/kg) while P. ostreatus (U6-8) greater zinc bioaccumulation (440.4 mg/kg) in mycelial biomass. P. ostreatus (U2-9), P. ostreatus (U2-11), and S. commune (U6-7) had the highest metal translocation rates from the culture medium to mycelial biomass. The mycelial biomass enriched with iron or zinc is an alternative to a new functional food from non-animal sources.

O presente trabalho avaliou a capacidade de adsorção do corante azul de metileno nos resíduos da palha de milho e da bainha do palmito pupunha in natura. A caracterização dos resíduos foi determinada utilizando-se a microscopia eletrônica de varredura e espectroscopia na região do infravermelho a qual indicou a presença de grupos carboxílicos, hidroxila e carbonila. O tempo necessário para que o sistema atingisse o equilíbrio para ambos os resíduos foi de 240 min, seguindo uma cinética descrita pelo modelo de pseudo-segunda ordem. A capacidade máxima de adsorção foi de 102,8 mg g-1 para o resíduo da palha de milho, seguindo o modelo de isoterma de Langmuir e 50,9 mg g-1 para o resíduo de palmito pupunha, sendo que o modelo que melhor se ajusta foi Freundlich. Desta forma, esses resíduos são promissores para a adsorção do corante azul de metileno em efluentes.

This study evaluated the ability of adsorption of methylene blue dye in waste of corn straw and sheath of palmetto pupunha in natura. The characterization of the waste was performed using MEV and spectroscopy in the infrared region, which indicated the presence of carboxyl groups, hydroxyl and carbonyl. The time required for the system to reach equilibrium for both residues was approximately 240 min, following the kinetics of pseudo-second order. The maximum adsorption capacity was 102.8 mg g-1 for corn straw, following the isotherm model of Langmuir and 50.9 mg g-1 for the residue of the sheath of palmetto pupunha, following the isotherm model of Freundlich. Thus, the wastes are promising for adsorption of methylene blue dye in effluents.

Pleurotus ostreatus is able to bioaccumulate several metals in its cell structures; however, there are no reports on its capacity to bioaccumulate iron. The objective of this study was to evaluate cultivation variables to increase iron bioaccumulation in P. ostreatusmycelium. A full factorial design and a central composite design were utilized to evaluate the effect of the following variables: nitrogen and carbon sources, pH and iron concentration in the solid culture medium to produce iron bioaccumulated in mycelial biomass. The maximum production of P. ostreatus mycelial biomass was obtained with yeast extract at 2.96 g of nitrogen L−1 and glucose at 28.45 g L−1. The most important variable to bioaccumulation was the iron concentration in the cultivation medium. Iron concentration at 175 mg L−1 or higher in the culture medium strongly inhibits the mycelial growth. The highest iron concentration in the mycelium was 3500 mg kg−1 produced with iron addition of 300 mg L−1. The highest iron bioaccumulation in the mycelium was obtained in culture medium with 150 mg L−1 of iron. Iron bioaccumulation in P. ostreatus mycelium is a potential alternative to produce non-animal food sources of iron.

Objetivou-se, neste trabalho, avaliar a eficácia do uso das sementes de crambe (Crambe abyssinica Hochst) como material adsorvente na remoção dos metais pesados tóxicos cádmio, chumbo e cromo de soluções contaminadas. Obteve-se a torta a partir da extração do óleo das sementes de crambe em sistema tipo Soxhlet. Nos testes cinéticos as massas do adsorvente variaram em soluções contendo os metais em condições de pH 5.0 e 7.0. As concentrações dos metais foram determinadas por espectrometria de absorção atômica modalidade chama (EAA/chama). De acordo com as condições ótimas encontradas ensaios de adsorção foram realizados para a construção das isotermas de cada metal as quais, por sua vez, foram linearizadas conforme os modelos matemáticos de Langmuir e Freundlich. Com base nos resultados obtidos concluiu-se que o adsorvente foi eficaz na remoção dos metais estudados em soluções aquosas, sendo viável sua utilização como material alternativo para adsorção dos metais pesados, além de se tratar de um coproduto que não sofreu tratamento prévio algum.

This study aimed to evaluate the efficacy of crambe seeds (Crambe abyssinica Hochst) as adsorbent material in the removal of the toxic metals cadmium, lead and chromium from contaminated solutions. The byproduct was obtained from oil extraction of crambe seeds in a Soxhlet system. In kinetic tests, the adsorbent masses had varied in solutions containing the metals under pH 5.0 and 7.0. Metal concentrations were determined by flame atomic absorption spectrometry (FAAS). According to optimal conditions found, the adsorption assays were performed for obtaining the isotherms of each metal, which were linearized in agreement with the mathematical models of Langmuir and Freundlich. According to the obtained results, the adsorbent was effective in removing the assessed metals in aqueous solutions, being feasible its employment as an alternative material for the adsorption of metals, besides being a byproduct, which has undergone no prior treatment.

Este estudo objetivou avaliar a eficácia do uso da torta de moringa (Moringa oleifera Lam.) como material adsorvente dos metais pesados tóxicos cádmio (Cd), chumbo (Pb) e cromo (Cr) de soluções contaminadas. Nos testes cinéticos foram variadas as massas do adsorvente em duas condições de pH (5,0 e 7,0). As condições otimizadas foram pH 5,0 e massa de 0.300 g de adsorvente, utilizados para a construção das isotermas e linearizadas conforme os modelos de Langmuir e Freundlich. Realizou-se a determinação dos metais por espectrometria de absorção atômica. Os resultados mostraram que houve semelhança em ambos os modelos utilizados para a adsorção do Cd. Para o Pb, o modelo de Freundlich apresentou o melhor ajuste e, para o Cr, houve melhor ajuste pelo modelo de Langmuir. Conclui-se, com base nos resultados obtidos, que o adsorvente foi eficaz na remediação de soluções contendo Cd, Pb e Cr e, assim, é viável a utilização desse adsorvente como material alternativo sustentável, pois apresenta baixo custo, não necessita de tratamento prévio e se trata de um coproduto.

This study evaluated the efficacy of moringa seeds (Moringa oleifera Lam.) as an adsorbent material for removing toxic heavy metals such as cadmium, lead, and chromium from contaminated solutions. The effect of the adsorbent mass was investigated at two pH conditions (5.0 and 7.0). The optimized conditions were 0.300 g of adsorbent at pH 5.0, used for the isotherms construction, and linearized according to Langmuir and Freundlich models. Results showed that cadmium adsorption was similar in both the models used. For lead, the Freundlich model had the best adjustment and chromium was better adjusted by the Langmuir model. It was concluded that the adsorbent was effective in the remediation of solutions containing cadmium, lead and chromium, thus, its use as sustainable alternative material is feasible, since it has low cost, does not need a previous treatment and it is a byproduct.

Objetivou-se, neste trabalho, analisar a eficiência de resíduos de macadâmia (mesocarpo e endocarpo) com e sem modificações químicas na biossorção de íons cobre II. As modificações químicas no biossorvente foram realizadas com hidróxido de sódio (NaOH) e com NaOH mais ácido cítrico e comprovadas por espectroscopia na região do infravermelho, pela presença dos picos em 1710 e 1420 cm-1 como também pela microscopia eletrônica de varredura (MEV) observando-se aumento da rugosidade na superfície. Os melhores resultados de biossorção foram para o mesocarpo modificado com NaOH, em pH igual a 5. O tempo de equilíbrio adsorvente-adsorbato foi de 140 min; além disto, o sistema seguiu um modelo cinético de pseudo-segunda ordem e a capacidade máxima de biossorção foi de 28,82 mg g-1. As isotermas para os resíduos modificados com NaOH seguiram o modelo de Langmuir e as modificadas com ácido se ajustaram ao modelo de Freundlich. Constatou-se que o processo de biossorção foi espontâneo energeticamente devido aos valores negativos para a energia de Gibbs. Comprovou-se, então, que o adsorvente possui alta capacidade de dessorção; assim, este material poderá ser novamente reutilizado; portanto, este resíduo poderá, futuramente equipar, filtros para remoção de Cu2+.

The objective was to analyze the efficiency of macadamia waste with and without chemical changes in biosorption of copper II (Cu2+). The chemical changes in the biosorbent with sodium hydroxide (NaOH) and with NaOH and citric acid were evidenced by infrared spectroscopy by the appearance of peaks in 1710 and 1420 cm-1 and by scanning electron microscopy, observed an increase of roughness on the surface. The best results of the adsorption were observed in mesocarp modified with NaOH, in pH equal to 5. An equilibrium time adsorbent - adsorbate was 140 min, in addition, the system followed a kinetic model of pseudo-second order and the maximum adsorption capacity was 28.82 mg g-1. The isotherms for the residues modified with NaOH followed the Langmuir model and the modified with acid were adjusted to the Freundlich model. It was found that the adsorption process was energetically spontaneous due to negative values for the Gibbs energy and the adsorbent has a high capacity of desorption, so this material can be reused. Therefore, this residue is an excellent material to equip future filters for removal of copper II.

No presente trabalho, foi investigado o comportamento do extrato aquoso e alcoólico da beterraba (Beta vulgaris) como um indicador ácido-base, tendo como objetivo principal despertar o interesse pelo uso dos indicadores naturais, como alternativa didática para transmissão dos conceitos de titulação, equilíbrio químico e a lei de Lambert-Beer. Para a realização dos experimentos foram utilizadas soluções padrão de ácido clorídrico (HCl), ácido acético e hidróxido de sódio (NaOH). Inicialmente foram feitos testes para avaliar a reversibilidade do sistema, e observou-se que a coloração passa de vermelho para amarela com adição de base e retorna para vermelho com adição do ácido, sendo possível sua utilização para explicação do equilíbrio químico. As análises de espectroscopia UV-vis mostraram que os espectros de absorção molecular na região do visível, apresentam diferentes característica, dando indícios que ocorreu modificação na estrutura do indicador em meio ácido e básico. Após as análises volumétricas constatou-se que os pontos de equivalência determinados com o indicador natural tiveram concordância com os obtidos pelo método potenciométrico. Além disso, os extratos aquosos e alcoólicos da beterraba apresentam potencial didático para a explicação da lei de Lambert-Beer, sendo que no meio ácido houve uma melhor correlação comparado com o meio básico.

In this study, we investigated the behavior of aqueous and alcoholic extract of sugar beet (Beta vulgaris) as an acid-base indicator, having as main objective the awakening interest in the use of natural indicators as an alternative to teaching of concepts of titration, equilibrium chemical and the law of Lambert-Beer. For the experiments we used standard solutions of hydrochloric acid (HCl), acetic acid and sodium hydroxide (NaOH). Initially tests were performed to evaluate and reversibility of the system, and it was observed that the color changes from red to yellow with the addition of base and returns to red with acid addition, so can be used to explain the chemical equilibrium. The analysis of UV-vis spectra showed that the molecular absorption in the visible region, have different characteristics, giving evidence that was altered structure of the indicator in acidic and basic medium. After the titration was found that the points of equivalence with the natural indicator showed concordance with those obtained by potentiometric method. Furthermore, the aqueous and alcoholic extract of beet has a good correlation for Beer-Lambert law, being that the acidic medium presented a better correlation compared with basic.