RESUMO
Lipases from Thermomyces lanuginosus (TLL) and Pseudomonas fluorescens (PFL) wereimmobilized on functionalized silica particles aiming their use in the synthesis of fructose oleate in a tert-butyl alcohol/water system. Silica particles were chemically modified with octyl (OS), octyl plus glutaraldehyde (OSGlu), octyl plus glyoxyl(OSGlx), and octyl plus epoxy groups(OSEpx). PFL was hyperactivated on all functionalized supports (more than 100% recovered activity) using low protein loading (1 mg/g), however, for TLL, this phenomenon was observed only using octyl-silica (OS). All prepared biocatalysts exhibited high stability by incubating in tert-butyl alcohol (half-lives around 50 h at 65 °C). The biocatalysts prepared using OS and OSGlu as supports showed excellent performance in the synthesis of fructose oleate. High estersynthesis was observed when a small amount of water (1%, v/v) was added to the organic phase, allowing an ester productivity until five times (0.88-0.96 g/L.h) higher than in the absence of water (0.18-0.34 g/L.h) under fixed enzyme concentration (0.51 IU/g of solvent). Maximum ester productivity (16.1-18.1 g/L.h) was achieved for 30 min of reaction catalyzed by immobilized lipases on OS and OSGlu at 8.4 IU/mL of solvent. Operational stability tests showed satisfactory stability after four consecutive cycles of reaction.
Assuntos
Enzimas Imobilizadas , Frutose/química , Lipase/metabolismo , Ácido Oleico/síntese química , Dióxido de Silício , Biocatálise , Estabilidade Enzimática , Lipase/química , Modelos Moleculares , Conformação Molecular , Solventes , ÁguaRESUMO
This work reports the optimization of geranyl propionate production by esterification of geraniol and propionic acid in a solvent-free system using a commercial lipase as catalyst. For this purpose, a sequential strategy was performed applying two experimental designs. The operating conditions that optimized geranyl propionate production were determined to be 40 °C, geraniol to propionic acid molar ratio of 3:1, 150 rpm and 10 wt% of enzyme, with a resulting reaction conversion of about 93%. After determining the optimum reaction parameters, a kinetic study was carried out evaluating the influence of substrates molar ratio, enzyme concentration and temperature on reaction conversion. Results obtained in this step allow to conclude that an excess of alcohol (acid to alcohol molar ratio of 1:6), relatively low enzyme concentration (5 wt%), temperature of 40 °C and substrates molar ratio of 1:1 afforded nearly complete reaction conversion after 30 min of reaction. New experimental data on enzymatic esterification of geraniol and propionic acid for geranyl propionate production are reported in this work, showing a promising perspective of the technique to overcome the well-known drawbacks of the chemical-catalyzed route.
Assuntos
Lipase/metabolismo , Ácidos Oleicos/síntese química , Propionatos/síntese química , Propionatos/metabolismo , Solventes/química , Terpenos/metabolismo , Monoterpenos Acíclicos , Biotecnologia , Catálise , Enzimas Imobilizadas/química , Enzimas Imobilizadas/metabolismo , Esterificação , Proteínas Fúngicas , Cinética , Lipase/química , Ácido Oleico/síntese química , Propionatos/química , Temperatura , Terpenos/químicaRESUMO
Carnosic acid (1) has been shown to possess gastroprotective activity in vitro and in vivo. However, little is known of the gastroprotective effect or cytotoxicity of carnosic acid gamma-lactone (3). To determine structure-activity relationships, a series of 17 esters of 3 were prepared including aliphatic, aromatic, and heterocyclic derivatives. Also, two units of 3 were coupled with succinic and phthalic acid as linkers. The compounds were assessed for their gastroprotective effect in the HCl/EtOH-induced gastric lesions model in mice and for cytotoxicity in human lung fibroblasts, human adenocarcinoma AGS cells, and Hep G2 hepatocellular carcinoma cells. At a single oral dose of 40 mg/kg, the gastroprotective effect increased moderately with the length of the alkyl chain. The best effects were observed for the butyrate (9) and chloroacetate (6) derivatives. Activity of fatty acid esters increased with chain length but decreased with unsaturation. The best gastroprotective effect, with lowest cytotoxicity, was found for the palmitate (11) and oleate (12) derivatives.