RESUMO
This work reports the transesterification of soybean oil with ethanol using two commercial immobilized lipases under the influence of ultrasound irradiation. The experiments were performed in an ultrasonic water bath, following a sequence of experimental designs to assess the effects of temperature, enzyme and water concentrations, oil to ethanol molar ratio and output irradiation power on the reaction yield. Results show that ultrasound-assisted lipase-catalyzed transesterification of soybean oil with ethanol might be a potential alternative route to conventional alkali-catalyzed method, as high reaction yields (~90 wt.%) were obtained at mild irradiation power supply (~100 W), and temperature (60 °C) in a relatively short reaction time, 4h, using Lipozyme RM IM as catalyst. The repeated use of the catalyst under the optimum experimental condition resulted in a decay in both enzyme activity and product conversion after two cycles. The use of Novozym 435 led to lower conversions (about 57%) but the enzyme activity was stable after eight cycles of use, showing, however, a reduction in product conversion after the forth cycle.
Assuntos
Lipase/química , Lipase/efeitos da radiação , Compostos Orgânicos/química , Compostos Orgânicos/efeitos da radiação , Sonicação/métodos , Óleo de Soja/química , Óleo de Soja/efeitos da radiação , Ativação Enzimática/efeitos da radiação , Enzimas Imobilizadas , Esterificação/efeitos da radiação , Proteínas Fúngicas , Ondas de Choque de Alta Energia , Cinética , Doses de Radiação , Solventes/química , Solventes/efeitos da radiação , Especificidade por Substrato/efeitos da radiaçãoRESUMO
This work reports experimental kinetic data of solvent-free glycerolysis of olive oil using a commercial immobilized lipase (Novozym 435) under the influence of ultrasound irradiation. The experiments were performed in a mechanically stirred reactor under ultrasound irradiation, evaluating the effects of temperature (50-70 °C), enzyme concentration (2.5-10 wt%) and glycerol to oil molar ratio (0.8:1-3:1). Results show that ultrasound-assisted lipase-catalyzed glycerolysis might be a potential alternative route to conventional methods, as high contents of reaction products, especially monoglycerides, were achieved at mild irradiation power supply (~130 W) and temperature, in a relatively short reaction time (2h) and low enzyme content (7.5 wt%). To completeness, two simplified kinetic modeling approaches, based on the ordered-sequential bi bi mechanism and reaction stoichiometry, were employed to represent the experimental data, thus allowing a better understanding of the reaction kinetics.
Assuntos
Glicerol/química , Glicerol/efeitos da radiação , Lipase/química , Lipase/efeitos da radiação , Óleos de Plantas/química , Óleos de Plantas/efeitos da radiação , Sonicação/métodos , Ativação Enzimática/efeitos da radiação , Enzimas Imobilizadas , Proteínas Fúngicas , Ondas de Choque de Alta Energia , Cinética , Azeite de Oliva , Doses de Radiação , Solventes , Especificidade por Substrato/efeitos da radiaçãoRESUMO
Interactions between tumor cells and their substratum influence cancer progression by modulating cell proliferation and survival. We now investigated whether signaling responses to UV irradiation differ on adhesion-permissive or restrictive substrates. The latter conditions diminished spreading and proliferation of neo 6.3/C8161 melanoma in which metastasis is suppressed by introduction of neo-tagged chromosome 6, but permitted proliferation of human metastatic C8161 melanoma. Apoptosis-associated PARP cleavage and DNA fragmentation induced by UV irradiation were diminished on the restrictive substrate in C8161 melanoma. Genotoxic responses to UV irradiation like persistent increases in the phosphorylation of histone H2AX, induction of the tumor suppressor p53 protein and greater binding of this protein to its DNA consensus sequence, were all decreased on the restrictive substrate. The latter also promoted a 2 fold increase of DNA condensation in chromatin and enhanced activation of the survival - and invasion-associated MMP-9 gelatinase B, preferentially in metastatic C81261 melanoma. Our data suggest that adaptation to restrictive substrates in metastatic C8161 melanoma decreases UV-induced apoptosis, partly through attenuation of DNA damage signaling responses and changes in genomic organization.