RESUMO
The accumulation of zinc (Zn) in Cichorium intybus and effects of phytotoxicity during 90 days of growth on (natural) non-contaminated and Zn-contaminated soils were studied. The phytotoxicity effects were monitored by evaluating the leaf area, leaf biomass, leaf length and root length of the vegetable. The Zn concentrations ranged from 5.35 ± 1.05 to 37.5 ± 3.89 mg kg-1 in leaves of plants grown on natural soil, and from 334.0 ± 25.6 to 2232 ± 16.7 mg kg-1 when grown on Zn-contaminated soils. Zn accumulation caused a decrease in growth on contaminated soils and an increase in phytotoxicity. These effects were associated to high metal concentration, mobility and bioavailability in the soil as well as changes in the translocation mechanism from the roots to the leaves. Then, it must be avoided the organic fertilization of soils with either animal manure or other agricultural inputs containing high zinc concentrations.
Assuntos
Cichorium intybus/efeitos dos fármacos , Poluentes do Solo/toxicidade , Zinco/toxicidade , Animais , Disponibilidade Biológica , Cichorium intybus/metabolismo , Fertilizantes , Metais , Folhas de Planta/química , Raízes de Plantas/química , Plantas , Solo , Poluentes do Solo/análise , Verduras , Zinco/análiseRESUMO
A full-factorial central composite rotational design (FFCCRD) was applied for studying the immobilization of lactase in Arabic gum-based and chitosan-based hydrogels, and hydrolysis of lactose. The optimal immobilization capacities of both hydrogels aiming to obtain high immobilized enzyme activity and low released fraction were determined at 25.0⯰C, 39.88â¯mgâ¯mL-1 initial enzyme concentration and pHâ¯6.5. The immobilized enzyme activity and released fraction from the Arabic gum-based hydrogel were 0.322â¯Uâ¯mg-1 and 0.193, respectively, during the hydrolysis of lactose contained in UHT milk. These values were 0.289â¯Uâ¯mg-1 and 0.136, respectively, using a chitosan-based hydrogel. The immobilized enzyme activity and released fraction from these hydrogels during the hydrolysis of standard lactose were 0.246â¯Uâ¯mg-1 and 0.407, and 0.211â¯Uâ¯mg-1 and 0.245, respectively. The best conditions for the immobilization of lactase and hydrolysis of lactose were achieved by applying FFCCRD, which were compared with experimental results.
Assuntos
Enzimas Imobilizadas , Hidrogéis/química , Lactase/química , Lactose/química , Polissacarídeos/química , Quitosana , Ativação Enzimática , Hidrogéis/síntese química , Concentração de Íons de Hidrogênio , Hidrólise , Cinética , TemperaturaRESUMO
Arabic gum-based and chitosan-based hydrogels were synthesized through chemical crosslinking for the immobilization and controlled release of bovine serum albumin (BSA) and characterized by Fourier-transform infrared spectrometry, scanning electron microscopy and swelling assays. The degrees of swelling of the Arabic gum-based hydrogel were 13.22 and 22.95â¯g water per g dried hydrogel at pHâ¯4.5 and 7.0, respectively, whereas the degrees of swelling of the chitosan-based hydrogel were 15.32 and 36.10â¯g water per g dried hydrogel, respectively. The water absorption mechanism in both hydrogels was non-Fickian, which involves diffusion through pores and macromolecular relaxation of the hydrophilic three-dimensional polymer network. BSA immobilization capacities of the Arabic gum-based and chitosan-based hydrogels after 240â¯min at pHâ¯4.5 were 71.0 and 175.6â¯mg protein per g dried hydrogel, respectively. BSA immobilization capacities after 240â¯min at pHâ¯7.0 were 62.5 and 154.2â¯mg protein per g dried hydrogel, respectively. The controlled release of BSA from the Arabic gum-based hydrogel was slightly more efficient than that of the chitosan-based hydrogel due to its more porous structure and weaker physiochemical interactions between the polymer network and protein molecule. Both hydrogels could be employed as carriers of proteins and as capsules for food supplements.
Assuntos
Quitosana/química , Preparações de Ação Retardada/química , Glicoconjugados/química , Goma Arábica/química , Hidrogéis/química , Soroalbumina Bovina/química , Acrilamida/química , Acrilamidas/química , Acrilatos/química , Animais , Bovinos , Reagentes de Ligações Cruzadas/química , Preparações de Ação Retardada/síntese química , Composição de Medicamentos , Liberação Controlada de Fármacos , Humanos , Hidrogéis/síntese química , Concentração de Íons de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Cinética , Porosidade , MolhabilidadeRESUMO
ß-d-galactosidase was immobilized in a modified Arabic gum-based hydrogel for the hydrolysis of standard lactose and lactose contained in UHT milk with the aim of producing lactose-free/low-lactose milk. The hydrogel was synthesized by cross-linking the modified Arabic gum with acrylamide, using potassium persulfate as initiator. Fourier-transform infrared spectroscopy and scanning electron microscopy confirmed the formation of the hydrogel and its three-dimensional porous network. Swelling degrees in distilled water, drinking water, phosphate buffer solution at pH7.0 and acetate buffer solution at pH4.0 were 12.56 and 17.72, 10.65 and 12.58, 8.58 and 10.71, and 6.49 and 8.16g water per g dried hydrogel at room temperature and 37.0±1.0°C, respectively. The immobilization capacities of ß-d-galactosidase in acetate and phosphate buffer solutions at room temperature were 242.52±0.13 and 118.42±0.23mg enzyme per g dried hydrogel, respectively, after 1440min of contact. Higher enzymatic activities were found after immobilization in phosphate buffer solution due to the isoelectric point of ß-d-galactosidase. Hydrolysis of standard lactose and lactose contained in UHT milk was more efficient using immobilized ß-d-galactosidase than free ß-d-galactosidase. Immobilized ß-d-galactosidase was applied for three cycles of hydrolysis of lactose without significantly losing enzymatic activity.