Engenharia Química
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/25
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8 resultados
Resultados da Pesquisa
- DSC characterization of enzymatic digestion of corneas treated with plant extracts rich in polyphenols(2019) Bersanetti P.A.; da Cruz L.G.I.; Carlstron R.; Schor P.; Morandim-Giannetti A.A.© 2019, Akadémiai Kiadó, Budapest, Hungary.Keratoconus is a progressive disease that affects patients’ quality of life by producing corneal irregular astigmatism and low vision as the cornea becomes thinner and presents a conical protrusion. Inducing cross-linking in keratoconic corneal stroma is the current preventive intervention that effectively blocks the progression of this ectasia. As a result of this process, there is an increase in biomechanical strength and resistance of the cornea. In this context, two plant extracts rich in polyphenols (Euterpe oleracea and Stryphnodendron adstringens) have been tested in this study to compact and stiffen the tissue, and its effect was evaluated by enzymatic digestion of porcine corneas. Thermal analysis by DSC was employed to verify the corneal resistance to degradation induced by the plant extracts. The values of temperature and enthalpy of denaturation at the initial time were: 65.6 ± 0.3 °C/3.8 ± 0.3 J g−1; 79.4 ± 0.5 °C/5.5 ± 0.4 J g−1; and 93.1 ± 1.2 °C/8.0 ± 0.6 J g−1, respectively, for the control, E. oleracea, and S. adstringens groups. After 24 h of collagenase digestion, these values were: 60.1 ± 0.8 °C/1.3 ± 0.1 J g−1; 78.1 ± 1.0 °C/5.6 ± 0.6 J g−1; and 93.2 ± 0.6 °C/8.1 ± 0.06 J g−1, respectively. These results show that there was no decrease in temperature and enthalpy of denaturation (p < 0.01) in corneas of the groups treated with the E. oleracea or S. adstringens extracts. However, in the control group, the temperature and the enthalpy decreased by approximately 8% and 65%, respectively. Therefore, this work demonstrated for the first time that plant extracts rich in polyphenols were efficient in decreasing the digestion and increasing the denaturation temperature of corneas.
- Attainment and characterization of carboxymethyl chitosan hydrogels by enzymatic cross-linking(2019) Morandim-Giannetti A.A.; Wecchi P.O.; Silverio P.A.; Carlstron R.; Bersanetti P.A.© 2019, Akadémiai Kiadó, Budapest, Hungary.In this study, carboxymethyl chitosan hydrogels (CMCH) cross-linked with catechin in the presence of laccase (CMCH-C-L) were obtained. The synthesis and characterization of CMCH were carried out from chitosan (CH) and its cross-linking with catechin (C) in the presence of laccase (L). DSC, ATR-FTIR, and rheological analyses of the CMCH solution and CMCH-C-L hydrogel were carried out. Three main thermal events were observed in the DSC characterization with temperatures and enthalpies related to each event for CMCH: 167.2 °C/+ 523.3 J g−1, 269.1 °C/− 35.0 J g−1, and 333.3 °C/− 17.6 J g−1, possibly referring to these processes: polymerization, breaking of electrostatic interactions, and decomposition of the material, respectively. The CMCH-C-L hydrogel presented values of 165.2 °C/+ 376.6 J g−1, 266.7 °C/− 47.8 J g−1, and 333.3 °C/− 31.5 J g−1. Conversely, the chitosan presented only one thermal event of decomposition at 302.5 °C and enthalpy of − 258.5 J g−1. Rheological properties of the hydrogels (viscosities, consistency values, and flow indices) showed non-Newtonian pseudoplastic rheological behavior and that the viscosity increased approximately 150% after the reaction (134.25 mPa s for CMCH and 342.85 mPa s in CMCH-C-L) confirming the formation of cross-links after the addition of catechin and laccase. Morphological analyses of CMCH and CMCH-C-L films via SEM showed the modification of the material after the reaction with the catechin in the presence of laccase and corroborated with the results, confirming the presence of cross-links.
- Alkyd resin synthesis by enzymatic alcoholysis(2019) de Carvalho R.K.C.; Ortega F.S.; Morandim-Giannetti A.A.© 2019, Iran Polymer and Petrochemical Institute.The synthesis of an alkyd resin through an enzymatic alcoholysis provided by Novozym 435 was analyzed in this study. The alcoholyses were performed in different enzyme concentrations (2.63, 4.00, 6.00, 8.00, and 9.36%, based on oil’s mass), oil/glycerin ratios (1.68, 2.50, 3.50, 4.50, and 5.18 oil mol/glycerin mol), at temperatures (33.18, 40.00, 50.00, 60.00, and 66.82 °C) to determine the best reaction conditions for obtaining the highest percentage of monoacylglycerides and diacylglycerides [glycerin/vegetal oil ratio of 1:3.5 (mol/mol), at temperature of 56.73 °C, and 9.36% enzyme concentration based on oil’s mass (w/w)]. It was verified that 2 h was the ideal reaction time. Under the best alcoholysis condition, the alkyd resin was produced using phthalic anhydride and the product presented similar characteristics as the current resin produced by a chemical catalyst in the industrial process (final viscosity = Y2, solid content = 44.00%, and IA ≤ 12). 1H NMR and FTIR analyses confirmed the formation of an alkyd resin as they showed the presence of characteristic signals of the final product. The re-usability of the enzyme was investigated, and significant results were observed in the reaction after five cycles (by activity reduction of 6%) showing the viability of applying enzymatic steps in industrial procedures to produce resins in the future, once the application of enzymes also reduced the level of toxicity in the processes.
- Attainment of cellulose acetate from coir fiber submitted to pretreatment with IL n-butylammonium acetate(2019) de Andrade Neto J.C.; de Almeida A.C.; dos Santos Machado C.; Coelho D.O.; Mourad N.; Teixeira N.S.; Pereira G.J.; Morandim-Giannetti A.A.© 2019, Iran Polymer and Petrochemical Institute.Cellulose acetate was obtained from the coir fiber submitted to the treatment with the IL. The coir fiber was initially subjected to treatment with the n-butylammonium acetate IL (CFIL) and subsequent bleaching (CFILB). By analyzing the CFILB, it was possible to observe a delignification of 6.10% in relation to the natural material and an 8.1% increase in the concentration of cellulose. The results from SEM, XRD, and FTIR-ART confirm the modifications in the fiber. After characterizing the treated coir fiber and obtaining the cellulose acetate, analyses by NMR confirmed its regeneration with a degree of substitution at 2.92. FTIR analyses corroborate with the obtained data, verifying the presence of the main adsorption bands. The XRD analysis of cellulose acetate shows peaks at 8.5° regarding the randomness after the acetylation of cellulose, as well as peaks between 18° and 22.5° regarding the packing of carbon atoms due to the Van der Waals forces, which confirm the production of cellulose acetate. The thermal analysis shows that decomposition events occurred in two stages, indicating the thermal decomposition of the remaining cellulose, which did not undergo acetylation, and attribution to its thermal degradation.
- DSC characterization of rabbit corneas treated with Stryphnodendron adstringens (Mart.) Coville extracts(2018) da Cruz L.G.I.; Moraes G.A.; Nogueira R.F.; Morandim-Giannetti A.A.; Bersanetti P.A.© 2017, Akadémiai Kiadó, Budapest, Hungary.Keratoconus is an eye ectasia that affects the cornea causing distortion of vision. Corneal crosslinking promoted by riboflavin photo-stimulated at 365 nm is a treatment used successfully to block the keratoconus progression. In this study, we characterize rabbit corneas subjected to enhanced crosslinking using different vegetable extracts prepared from Stryphnodendron adstringens (Mart.) Coville bark by differential scanning calorimetry. The extracts tested in this study were: aqueous, ketonic, ethanolic, ethyl acetate and hydroalcoholic, which revealed high levels of polyphenols, such as proanthocyanidins. The corneas, obtained from the slaughter rabbits, were divided into groups: control (consisting of untreated corneal samples) and S. adstringens, where the samples were subjected to 4% vegetable extracts for 2 h. The DSC profiles of the corneas were obtained in nitrogen atmosphere. The results showed that temperature and enthalpy of denaturation of the corneal samples treated with S. adstringens were higher than the control group. The control group presents temperature and enthalpy values of 59.8 ± 1.1 °C and 24.6 ± 2.7 J g−1, respectively. After crosslinking with ketone extract, the values were 90.1 ± 1.1 °C and 39.9 ± 2.7 J g−1. These results show that S. adstringens is efficient to increment the crosslinking level of the corneas.
- Pretreatment of Guinea grass (Panicum maximum) with the ionic liquid 1-ethyl-3-methyl imidazolium acetate for efficient hydrolysis and bioethanol production(2018) Odorico F.H.; Morandim-Giannetti A.A.; Lucarini A.C.; Torres R.B.© 2018, Springer Science+Business Media B.V., part of Springer Nature.In the present study, we pretreated the plant Guinea grass (Panicum maximum) with the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate [EMIM][OAc] to expose its cellulose fibers. For this, we first determined the composition of Guinea grass, with 6.87 ± 1.21% of ash, 14.33 ± 1.18% of lignin, 70.55 ± 1.15% of holocellulose, 29.9 ± 1.20% of cellulose, and 40.65 ± 1.20% of hemicellulose. After characterizing the material, we determined the IL pretreatment conditions that maximized the enzymatic and acid hydrolysis stages [namely: temperature = 157 °C, reaction time = 30 min, and biomass concentration (relative to total mass) = 14%]. Under these conditions, the enzymatic hydrolysis conversions of glucose and total reducing sugars were respectively 69.8 and 54.2%, determined by enzymatic and DNS methods. The acid hydrolysis was also carried out, and conversions of 57.4 and 27.2% were verified by the enzymatic and DNS methods, respectively. Finally, the hydrolysate obtained after the enzymatic hydrolysis was fermented by the yeast Saccharomyces cerevisiae, and the ethanol yield (81.9%) was determined through gas chromatography.
- Characterization of Rabbit Corneas Subjected to Stromal Stiffening by the Açaí Extract (Euterpe oleracea)(2017) Bersanetti P.A.; Bueno T.L.N.; Morandim-Giannetti A.A.; Nogueira R.F.; Matos J.R.; Schor P.© 2016 Taylor & Francis.Purpose: In this study, we characterized rabbit corneas subjected to corneal cross-linking (CXL) with açaí extract compared with a riboflavin photo-stimulated procedure. Materials and Methods: The corneas of the slaughterhouse rabbits were divided into three groups: control, consisting of untreated corneal samples; riboflavin/UVA, where corneas were treated with 0.1% riboflavin photo-stimulated at 365 nm as the standard protocol; and açaí, where the samples were subjected to 4% açaí extract for 0.5–2 h. After the CXL procedure, corneas of the three groups were characterized by analyzing their elastic modulus and thermal denaturation profile. Results: The elastic modulus at 3% strain showed an approximately threefold increase in the riboflavin/UVA group and 10.5 times in the corneas treated with 4% açaí extract for 2 h, compared with the control group (p < 0.01). The denaturation temperature values of the two groups of crosslinked corneas increased significantly (p < 0.05) and were more pronounced in the açaí group. Conclusions: The açaí extract was effective in promoting CXL in rabbit corneas as characterized by the different techniques.
- Lignin as additive in polypropylene/coir composites: Thermal, mechanical and morphological properties(2012) Morandim-Giannetti A.A.; Agnelli J.A.M.; Lancas B.Z.; Magnabosco R.; Casarin S.A.; Bettini S.H.P.PP/CF composites were prepared and the effect of lignin incorporation in the presence and absence of compatibilizer (maleic anhydride grafted polypropylene, PP-g-MA) was investigated by means of mechanical, thermal and morphological properties. Lignin added to the composite was obtained by the Acetosolv process. The composites were prepared in a Haake torque rheometer and assessed by means of tensile testing, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The results showed that in the absence of PP-g-MA, incorporation of lignin did not affect tensile strength and in its presence this property was reduced. Thermal analysis revealed that incorporation of lignin in the composites resulted in increase in both the initial thermal decomposition temperatures and oxidation induction times. © 2011 Elsevier Ltd.