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991.
α-Amylase from Aspergillus oryzae was covalently immobilized onto polystyrene pellets with pentaethylenehexamine (PS-PEHA-Ald) and pentaethylene glycol (PS-PG-Ald) carrying a terminal aldehyde group. Optimum immobilization occured at pH 8.0 and 25 °C, and at pH 7.0 and 35 °C for PS-PEHA-Ald and PS-PG-Ald, respectively. PS-PEHA-Ald immobilized enzyme retained approximately 75% of the initial activity over 45 days of storage, 70% of the initial activity after nine runs of recycling and displayed the better resistance to detrimental metal ions. PS-PG-Ald immobilized enzyme retained approximately 50% of the initial activity in 8h at 70 °C. The catalytic efficiencies of PS-PEHA-Ald immobilized and PS-PG-Ald immobilized amylase were 1.42 and 1.29 times higher than that of native enzyme. The activation energy of the reaction mediated by the amylase was reduced by 58.1% and 57.3% when PS-PEHA-Ald and PS-PG-Ald used as support respectively. 相似文献
992.
993.
Supercritical CO2 (SC-CO2), a green solvent suitable for a mobile lignocellulosic biomass processor, was used to pretreat corn stover and switchgrass at various temperatures and pressures. The CO2 pressure was released as quickly as possible by opening a quick release valve during the pretreatment. The biomass was hydrolyzed after pretreatment using cellulase combined with β-glucosidase. The hydrolysate was analyzed for the amount of glucose released. Glucose yields from corn stover samples pretreated with SC-CO2 were higher than the untreated sample’s 12% glucose yield (12 g/100 g dry biomass) and the highest glucose yield of 30% was achieved with SC-CO2 pretreatment at 3500 psi and 150 °C for 60 min. The pretreatment method showed very limited improvement (14% vs. 12%) in glucose yield for switchgrass. X-ray diffraction results indicated no change in crystallinity of the SC-CO2 treated corn stover when compared to the untreated, while SEM images showed an increase in surface area. 相似文献
994.
Stereoselective degradation of Diclofop-methyl (DM) has been found in alcohol fermentation of grape must and sucrose solution with dry yeast. A method was developed for separation and determination the two enantiomers of DM during the fermentation process by high-performance liquid chromatography based on cellulose tri-(3,5-dimethylphenyl-carbamate) chiral stationary phase. The results showed that the enantiomers of DM degraded following the first-order kinetics in the sucrose solution and the degradation of DM enantiomers in grape must were biphasic (slow-fast-slow process). In the sucrose solution, half lives of (+)-(R)-DM and (-)-(S)-DM were calculated to be 8.5 h and 3.1 h, respectively. In the grape must, half life of (+)-(R)-DM was calculated to be 41.7 h while (-)-(S)-DM was 16.0 h. The result was that (-)-(S)-enantiomer degraded faster than the (+)-(R)-enantiomer in both alcohol fermentation. The results also showed that the differences of the enantioselective degradation of DM depended on the fermentation matrix. DM was configurationally stable in fermentation, showing no interconversion of (-)-(S)- to (+)-(R)- enantiomer, and vice-versa. 相似文献
995.
Hailei W Zhifang R Ping L Yanchang G Guosheng L Jianming Y 《Bioresource technology》2011,102(10):6082-6087
Co-culture of Penicillium sp. HSD07B and Candida tropicalis resulted in the production of a red pigment consisting of six components as determined by TLC and HPLC. The pigment showed no acute toxicity in mice and was mot mutagenic in the Ames test. The pigment was stable between pH 2 and 10 and temperatures of 10-100 °C and exhibited good photo-stability and resistance to oxidization by hydrogen peroxide and reduction by Na2SO3. Glucose and ratio of C. tropicalis to strain HSD07B (w/w) in the inoculum were the important factors influencing production of the pigment. Under optimized conditions, a pigment yield of 2.75 and 7.7 g/l was obtained in a shake-flask and a 15 l bioreactor, respectively. Thus, co-culture of strain HSD07B and C. tropicalis is a promising way to produce a red pigment potentially useful for coloring applications. 相似文献
996.
Some common floating aquatic macrophytes could remove nutrients, such as nitrogen, from eutrophic water. However, the relationship between these macrophytes and the ammonia-oxidizing microorganisms on their rhizoplanes is still unknown. In this study, we examined communities of ammonia-oxidizing archaea (AOA) and bacteria (AOB) on the rhizoplanes of common floating aquatic macrophytes (Eichhornia crassipes, Pistia stratiotes and Ipomoea aquatic) in a eutrophic reservoir.The results show that AOB were the predominant ammonia-oxidizer on the three rhizoplanes. The principal AOB were Nitrosomonas europaea and Nitrosomonas ureae clades. The principal group of AOA was most similar to the clone from activated sludge. The ratio of AOB amoA gene copies to AOA varied from 1.36 (on E. crassipes) to 41.90 (on P. stratiotes). Diversity of AOA was much lower than that of AOB in most samples, with the exception of P. stratiotes. 相似文献
997.
Gao J Li X Gu G Sun B Cui M Ji M Lou HX 《Bioorganic & medicinal chemistry letters》2011,21(2):622-627
To investigate the relationship of cytotoxicity and saponins with varied aglycones, based on the structure of indioside E 1, a natural derived anti-tumor active ingredient from Chinese medicinal plant Solanum indicum L., five novel saponins 2-6 bearing the same trisaccharide moiety together with 1 were efficiently synthesized via a transglycosylation strategy. MTT assay revealed the killing effects to tumor cells of the synthesized saponins are varied with the change of aglycones. Furthermore, time-lapse microscopy, LDH release, PI staining, and immunocytochemical investigations demonstrated that the cell death caused by neosaponin 2 was through oncotic necrosis involving plasma membrane perturbation and destruction of cytoskeleton. 相似文献
998.
Ranyuk ER Cauchon N Ali H Lecomte R Guérin B van Lier JE 《Bioorganic & medicinal chemistry letters》2011,21(24):7470-7473
Sulfonated metallo phthalocyanines (MPcS(n)) are second generation photosensitizers advanced for photodynamic therapy of various medical applications. A series of ZnPcS(n) was demetallated and subsequently converted to the corresponding [(64)Cu]CuPcS(n) in 40-50% isolated yields and >98% radiochemical purities. Tumor-bearing mice were injected with the (64)Cu-labeled products and subjected to 3-h dynamic PET imaging studies. Biodistribution patterns showed characteristic differences between the various derivatives. Tumor uptake was detected only for the amphiphilic derivatives [(64)Cu]CuPcS(2) and [(64)Cu]CuPcS(3)C(6) (1-1.5%ID/g). The biological data suggest that PET imaging with [(64)Cu]CuPc can be used to establish structure-PDT efficacy relationships for Pc-based photosensitizers. 相似文献
999.
Yang Y Miller KJ Zhu Y Hong Y Tian Y Murugesan N Gu Z O'Tanyi E Keim WJ Rohrbach KW Johnghar S Behnia K Pelleymounter MA Carlson KE Ewing WR 《Bioorganic & medicinal chemistry letters》2011,21(22):6856-6860
Obesity remains a significant public health issue leading to Type II diabetes and cardiovascular disease. CB1 antagonists have been shown to suppress appetite and reduce body weight in animal models as well as in humans. Evaluation of pre-clinical CB1 antagonists to establish relationships between in vitro affinity and in vivo efficacy parameters are enhanced by ex vivo receptor occupancy data. Synthesis and biological evaluation of a novel and highly selective radiolabeled CB1 antagonist is described. The radioligand was used to conduct ex vivo receptor occupancy studies. 相似文献
1000.
Chen SY Chen Y Li YP Chen SH Tan JH Ou TM Gu LQ Huang ZS 《Bioorganic & medicinal chemistry》2011,19(18):5596-5604
A series of novel curcumin analogues were designed, synthesized, and evaluated as potential multifunctional agents for the treatment of AD. The in vitro studies showed that these compounds had better inhibitory properties against Aβ aggregation than curcumin. Superior anti-oxidant properties (better than the reference compound Trolox) of these compounds were observed by the oxygen radical absorbance capacity (ORAC) method and a cell-based assay using DCFH-DA as a probe. In addition they were able to chelate metals such as iron and copper and decrease metal-induced Aβ aggregation. The structure-activity relationships were discussed. The results suggested that our curcumin analogues could be selected as multifunctional agents for further investigation of AD treatment. 相似文献