RESUMO

This work applied BM as support for immobilization of lipase TLL in packed-bed reactor and its application for the synthesis of hexyl laurate. Initially, the percolation of a solution containing 5 mg of TLL at 25 oC generated an immobilized derivative with hydrolytic activity of 504.7 U/g and 31.7% of recovered activity. Subsequent treatment with n-hexane, as well as the effect of temperature on the immobilization process were able to improve the activities of the final BM-TLLF, achieving a hydrolysis activity of 7023 U/g and esterification activity of 430 U/g against 142 U/g and 113.5 U/g respectively presented by commercial TLIM. Desorption studies showed that the TL IM has 18 mg of protein per gram of support, compared to 4.92 mg presented by BM-TLL. Both biocatalysts were applied to synthesize hexyl laurate, achieving 98% conversion at 40°C within a residence time of 2 hours. Notably, BM-TLLF displayed exceptional recyclability, maintaining catalytic efficiency over 12 cycles. This reflects a productivity of 180 mg of product/h/U of the enzyme, surpassing 46 mg/h/U obtained for TLIM. These results demonstrate the efficacy of continuous flow technology in creating a competitive and integrated process offering an exciting alternative for the valorization of residual lignocellulosic biomass.

RESUMO

The high demand for food and energy imposed by the increased life expectancy of the population has driven agricultural activity, which is reflected in the larger quantities of agro-industrial waste generated, and requires new forms of use. Brazil has the greatest biodiversity in the world, where corn is one of the main agricultural genres, and where over 40% of the waste generated is from cobs without an efficient destination. With the aim of the valorization of these residues, we proposed to study the immobilization of laccase from Aspergillus spp. (LAsp) in residual corn cob and its application in the degradation of Remazol Brilliant Blue R (RBBR) dye. The highest yields in immobilized protein (75%) and residual activity (40%) were obtained at pH 7.0 and an enzyme concentration of 0.1 g.mL-1, whose expressed enzyme activity was 1854 U.kg-1. At a temperature of 60 °C, more than 90% of the initial activity present in the immobilized biocatalyst was maintained. The immobilized enzyme showed higher efficiency in the degradation (64%) of RBBR dye in 48 h, with improvement in the process in 72 h (75%). The new biocatalyst showed operational efficiency during three cycles, and a higher degradation rate than the free enzyme, making it a competitive biocatalyst and amenable to industrial applications.

Assuntos

Lacase , Zea mays , Antraquinonas/química , Corantes/química , Lacase/metabolismo , Zea mays/metabolismo

RESUMO

As a consequence of intense industrialization in the last few decades, the amount of agro-industrial wastes has increasing, where new forms of valorization are crucial. In this work, five residual biomasses from Maranhão (Brazil) were investigated as supports for immobilization of lipase from Thermomyces lanuginosus (TLL). The new biocatalysts BM-TLL (babaçu mesocarp) and RH-TLL (rice husk) showed immobilization efficiencies >98% and hydrolytic activities of 5.331 U g-1 and 4.608 U g-1, respectively, against 142 U g-1 by Lipozyme® TL IM. High esterification activities were also found, with 141.4 U g-1 and 396.4 U g-1 from BM-TLL and RH-TLL, respectively, against 113.5 U g-1 by TL IM. Results of porosimetry, SEM, and BET demonstrated BM and RH supports are mesoporous materials with large hydrophobic area, allowing a mixture of hydrophobic adsorption and confinement, resulting in hyperactivation of TLL. These biocatalysts were applied in the production of hexyl laurate, where RH-TLL was able to generate 94% conversion in 4 h. Desorption with Triton X-100 and NaCl confirmed that new biocatalysts were more efficient with 5 times less protein than commercial TL IM. All results demonstrated that residual biomass was able to produce robust and stable biocatalysts containing immobilized TLL with better results than commercial preparations.

Assuntos

Enzimas Imobilizadas/química , Eurotiales/enzimologia , Proteínas Fúngicas/química , Resíduos Industriais , Ácidos Láuricos/química , Lipase/química , Adsorção , Agricultura/métodos , Algoritmos , Biocatálise , Brasil , Enzimas Imobilizadas/metabolismo , Esterificação , Proteínas Fúngicas/metabolismo , Hidrólise , Interações Hidrofóbicas e Hidrofílicas , Ácidos Láuricos/síntese química , Ácidos Láuricos/metabolismo , Lignina/química , Lignina/metabolismo , Lignina/ultraestrutura , Lipase/metabolismo , Microscopia Eletrônica de Varredura , Modelos Químicos

RESUMO

This work investigates batch and continuous-flow heterogeneous catalytic hydrogenation of a mixture of cafestol and kahweol (C&K) to obtain pure cafestol. These diterpenes were extracted from green coffee beans, and hydrogenation was performed using well-established palladium catalysts (Pd/C, Pd/CaCO3, Pd/BaSO4, and Pd/Al2O3) and a carbon black-supported Pd catalyst coated by a covalently tethered SiO2 shell with mesoporous texture (Pd/CB@SiO2), all partially deactivated with quinoline. Pd/C 10% poisoned with 1 wt % quinoline gave the best result for batch reaction, producing cafestol from kahweol with high selectivity (>99%) after 10 min. Excellent selectivity was also obtained with the catalyst Pd/CB@SiO2 with only 1% Pd. In addition, Pd/C-quinoline adapted for continuous-flow experiments exhibited the best catalytic activity, also providing cafestol with excellent selectivity (>99%) after 9.8 s.

RESUMO

Among the several classes of chemical reactions, the green oxidation of organic compounds has emerged as an important topic in nanocatalysis. Nonetheless, examples of truly green oxidations remain scarce due to the low activity and selectivity of reported catalysts. In this paper, we present an approach based on the optimization of both the support material and the active phase to achieve superior catalytic performances towards green oxidations. Specifically, our catalysts consisted of ultrasmall Au NPs deposited onto MnO2 nanoflowers. They displayed hierarchical morphology, large specific surface areas, ultrasmall and uniform Au NPs sizes, no agglomeration, strong metal-support interactions, oxygen vacancies, and Auδ+ species at their surface. These features led to improved performances towards the green oxidations of CO, benzene, toluene, o-xylene, glucose, and fructose relative to the pristine MnO2 nanoflowers, commercial MnO2 decorated with Au NPs, and other reported catalysts. We believe that the catalytic activities, stabilities, and mild/green reaction conditions described herein for both gas and liquid phase oxidations due to the optimization of both the support and active phase may inspire the development of novel catalytic systems for a wealth of sustainable transformations.

RESUMO

Copper catalysts are very promising, affordable alternatives for noble metals in CO oxidation; however, the nature of the active species remains unclear and differs throughout previous reports. Here, we report the preparation of 8 nm copper nanoparticles (Cu NPs), with high metallic content, directly deposited onto the surface of silica nanopowders by magnetron sputtering deposition. The as-prepared Cu/SiO2 contains 85% Cu0 and 15% Cu2+ and was enriched in the Cu0 phase by H2 soft pretreatment (96% Cu0 and 4% Cu2+) or further oxidized after treatment with O2 (33% Cu0 and 67% Cu2+). These catalysts were studied in the catalytic oxidation of CO under dry and humid conditions. Higher activity was observed for the sample previously reduced with H2, suggesting that the presence of Cu-metal species enhances CO oxidation performance. Inversely, a poorer performance was observed for the sample previously oxidized with O2. The presence of water vapor caused only a small increase in the temperature require for the reaction to reach 100% conversion. Under dry conditions, the Cu NP catalyst was able to maintain full conversion for up to 45 h at 350 °C, but it deactivated with time on stream in the presence of water vapor.