RESUMO
The budC gene encoding the meso-2,3-BDH from Klebsiella pneumoniae XJ-Li was expressed in E. coli BL21 (DE3) pLys. Hypothetical amino acid sequence alignments revealed that the enzyme belongs to the short chain dehydrogenase/reductase family. After purification and refolding, the recombinant enzyme had activities of 218 U/mg for reduction of acetoin and 66 U/mg for oxidation of meso-2,3-butanediol. Highest activities were at pH 8.0 and 9.0 respectively. These are higher than other meso-2,3-butanediol dehydrogenases from K. pneumoniae. The low K (m) value (0.65 mM) for acetoin indicated that the enzyme can easily reduce acetoin to meso-2,3-butanediol. There were no significant activities towards 2R,3R-2,3-butanediol, 1,4-butanediol and 2S,3S-2,3-butanediol, suggesting that the enzyme has a high stereospecificity for the meso-dihydric alcohol.
Assuntos
Oxirredutases do Álcool/biossíntese , Oxirredutases do Álcool/química , Proteínas de Bactérias/biossíntese , Proteínas de Bactérias/química , Klebsiella pneumoniae/enzimologia , Oxirredutases do Álcool/genética , Oxirredutases do Álcool/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Butileno Glicóis/química , Butileno Glicóis/metabolismo , Clonagem Molecular , Eletroforese em Gel de Poliacrilamida , Escherichia coli/enzimologia , Escherichia coli/genética , Concentração de Íons de Hidrogênio , Klebsiella pneumoniae/genética , Oxirredução , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Especificidade por Substrato , TemperaturaRESUMO
Enzyme-assisted aqueous two-phase extraction (EA-ATPE) using ethanol/ammonium sulfate system was investigated for total polyphenol (TP) and lutein from marigold flowers. The important factors were investigated by single factor experiment and response surface methodology combined with Box-Behnken design to optimize the operating parameters of EA-ATPE. The maximum yields of TP and lutein were 83.56 ± 0.69 mg g-1 and 5.59 ± 0.13 mg g-1, respectively. Compared with aqueous two-phase extraction and Soxhlet extraction (SE), the extraction yield of TP by EA-ATPE is 64.91% higher and the extract of EA-ATPE has better antioxidant activity. The pretreatment effect was also researched by scanning electron microscopy. Thus, EA-ATPE is an efficient method for extracting bioactive components from plants.
Assuntos
Luteína/isolamento & purificação , Extratos Vegetais/isolamento & purificação , Polifenóis/isolamento & purificação , Tagetes/química , Sulfato de Amônio/química , Fracionamento Químico , Etanol/química , Flores/química , Luteína/análise , Extratos Vegetais/análise , Polifenóis/análiseRESUMO
Yangzonghai Lake is the third largest plateau lake in Yunnan province. In June 2008, arsenic contamination was detected in Yangzonghai Lake and the water quality worsens dramatically from standard grade II to worse than grade V. Since Yongzonghai Lake is so large with the area of 31 km2 and the storage capacity of 6.04 x 10(8) m3, those pretreatment operations of the traditional arsenic removal methods, such as pre oxidation, adjusting pH value, are not applicable. In this study, a facile remediation strategy for arsenic removal by coagulation process, in which ferric chloride was directly sprayed into the contaminated water without any pretreatment, was reported. The results showed that the arsenic removal percentage was up to 95.1%-96.7% for 50 L raw water with reagent dosage of 1.62-3.20 mg x L(-1). Furthermore, the pH value of the lake kept constant in the coagulation process, which was beneficial for fish survival. Re-dissolved arsenic from precipitation was not detected in 954 days. The strategy of ferric chloride coagulation were applied to field experiments for lake water with volumes of 1 x 10(4) m3 and 25 x 10(4) m3, in which arsenic was also removed effectively. The reported strategy was of great advantage for simple operation, low cost and ecological safety, therefore it provides a representative example for arsenic contamination treatment of large lake.
Assuntos
Arsênio/química , Recuperação e Remediação Ambiental/métodos , Lagos/química , Poluentes Químicos da Água/química , China , Cloretos , Compostos Férricos , Água DoceRESUMO
The microbial production of 1,3-propanediol (1,3-PD) by Klebsiella pneumoniae XJPD-Li under different aeration strategies were investigated. In batch fermentation, the results showed that the final concentration of 1,3-PD and yield on glycerol were 13.44 g/l and 0.73 mol/mol under the anaerobic condition (N2, 0.4 vvm), 11.55 g/l and 0.62 mol/mol without aeration, and 8.73 g/l and 0.47 mol/mol under the aerobic condition (air, 0.4 vvm), respectively. Under the aerobic condition, the yield of 1,3-PD on glycerol was the lowest, while the biomass (optical density at 650 nm) was the highest among these three conditions. In the fed-batch culture, the final concentration and the yield of 1,3-PD was 60.82 g/l and 0.61 mol/mol under the anaerobic condition (N2, 0.4 vvm), 56.43 g/l and 0.53 mol/mol without aeration, and 65.26 g/l and 0.56 mol/mol under the aerobic condition. All these three conditions had good productivities of 1,3-PD, which were 3.35 g/lxh under the anaerobic condition (N2, 0.4 vvm), 3.13 g/lxh without aeration, and 3.16 g/lxh under the aerobic condition within the initial 12 h.