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1.
When Saccharomyces cerevisiae was cultivated under ~200 g glucose/l condition, the time point at which glucose was completely utilized coincided with the moment at which the slope of a redox potential profile changed from negative or zero to positive. Based on this feature, a redox potential-driven glucose-feeding fermentation operation was developed, and resulted in a self-cycling period of 14.25 ± 0.4 h. The corresponding ethanol concentration was maintained at 88.4 ± 1.0 g/l with complete glucose conversion, and the cell viabilities increased from 80% in the transition period to 97.2 ± 1.1%, implying the occurrence of yeast acclimatization. In contrast, a pre-determined 36-h manually adjusted period was chosen to oscillate yeast cells under ~250 g glucose/l conditions, which resulted in 106.76 ± 0.7 g ethanol/l and 15.19 ± 1.3 g glucose/l remaining at the end of each cycle. Compared to the equivalent batch and continuous ethanol fermentation processes, the annual ethanol productivity of the reported fermentation operation is 2.4% and 13.2% greater, respectively in ~200 g feeding glucose/l conditions.  相似文献   

2.
《Process Biochemistry》2007,42(4):704-709
Four immobilized forms of glucose oxidase (GOD) were used for biotransformation removal of glucose from its mixture with dextran oligosaccharides. GOD was biospecifically bound to Concanavalin A-bead cellulose (GOD-ConA-TBC) and covalently to triazine-bead cellulose (GOD-TBC). Eupergit C and Eupergit CM were used for preparation of other two forms of immobilized GOD: GOD-EupC and GOD-EupCM. GOD-ConA-TBC and GOD-EupC exhibited the best operational and storage stabilities. pH and temperature optima of these two immobilized enzyme forms were broadened and shifted to higher values (pH 7 and 35 °C) in comparison with those of free GOD. The decrease of Vmax values after immobilization was observed, from 256.8 ± 7.0 μmol min−1 mgGOD−1 for free enzyme to 63.8 ± 4.2 μmol min−1 mgGOD−1 for GOD-ConA-TBC and 45 ± 2.7 μmol min−1 mgGOD−1 for GOD-EupC, respectively. Depending on the immobilization mode, the immobilized GODs were able to decrease the glucose content in solution to 3.8–15.6% of its initial amount The best glucose conversion, was achieved by an action of GOD-EupCM on a mixture of 100 g dextran with 9 g of glucose (i.e. 98.7% removal of glucose).  相似文献   

3.
An FAD-dependent glucose dehydrogenase (FAD-GDH) from Aspergillus terreus NIH2624 was expressed in Escherichia coli with a yield of 228 ± 16 U/L of culture. Co-expression with chaperones DnaK/DnaJ/GrpE and osmotic stress induced by simple carbon sources enhanced productivity significantly, improving the yield to 23883 ± 563 U/L after optimization. FAD-GDH was purified in two steps with the specific activity of 604 U/mg. Using d-glucose as substrate, the optimal pH and temperature for FAD-GDH were determined to be 7.5 and 50 °C, respectively. Activity was stable across the pH range 3.5–9.0, and the half-life was 52 min at 42 °C. Km and Vmax were calculated as 86.7 ± 5.3 mM and 928 ± 35 U/mg, and the molecular weight was approximately 65.6 kDa based on size exclusion chromatography, indicating a monomeric structure. The 3D structure of FAD-GDH was simulated by homology modelling using the structure of A. niger glucose oxidase (GOD) as template. From the model, His551, His508, Asn506 and Arg504 were identified as key residues, and their importance was verified by site-directed mutagenesis. Furthermore, three additional mutants (Arg84Ala, Tyr340Phe and Tyr406Phe) were generated and all exhibited a higher degree of substrate specificity than the native enzyme. These results extend our understanding of the structure and function of FAD-GDH, and could assist potential commercial applications.  相似文献   

4.
《Process Biochemistry》2004,39(11):1519-1524
Changes in pyruvate and ascorbate production and antioxidant enzyme activities together with lipid peroxidation levels in Fusarium equiseti were investigated in relation to changes in the concentrations of glucose and maltose as carbon sources in the range of 5–25 g/l in Armstrong Fusarium Medium (AFM). The highest pyruvate concentration obtained at 20 g/l maltose was 67.5 ± 0.69 μg/ml while ascorbic acid reached a maximum value at 25 g/l glucose of 1866±26.1 μg/ml The maximum superoxide dismutas (SOD) activities related to increased pyruvate production were determined in AFM medium containing 20 g/l glucose as 41.49±0.65 and maltose as 61.12±0.8 IU/mg. Catalase (CAT) activity variations showed coherence with SOD activity in a medium containing maltose and reached 219.11±2.8 IU/mg while they were decreased with increasing glucose concentration. glutathione peroxidase (GSH-Px) activities in F. equiseti did not change significantly with glucose and maltose concentration and were determined to be 1.21±0.22 and 1.67±0.15 IU/mg, respectively. Minimum lipid peroxidation levels for each carbon source were determined in both 20 g/l maltose and glucose concentrations as 0.9 and 1.62 nmol MDA/g wet weight.  相似文献   

5.
《Process Biochemistry》2007,42(8):1259-1263
We have investigated production, solubility and activity of recombinant glutathione-S-transferase (GST) expressed in Escherichia coli BL21 grown in defined media with glucose or glycerol as carbon source. GST was predominantly expressed as a soluble protein on both carbon sources, and 83–84% was found in the supernatant after cell lysis. In cultures grown on glucose, only 32 ± 9% of the GST was active, while 76 ± 13% of the GST was active in cultures grown on glycerol. This shows that glycerol has the potential to increase the activity of soluble GST in E. coli cultures in vivo.  相似文献   

6.
《Process Biochemistry》2014,49(4):673-680
Strain Trichoderma koningii D-64 was improved for enhanced cellulase production. A potential mutant MF6 was obtained and its enzymes contained filter paper cellulase (FPase), carboxymethylcellulase (CMCase), β-glucosidase and xylanase with respective activities of 2.0, 1.3, 2.0 and 3.0 folds of those for the parental strain. MF6 cellulases showed enhanced hydrolysis performance for the treated lignocellulosic biomass. Hydrolysis of treated oil palm empty fruit bunch (OPEFB), horticulture wastes (HW) and wood chips (WC) resulted in cellulose to glucose conversion of 96.3 ± 2.2%, 98.2 ± 3.0% and 81.9 ± 1.4%, respectively. The corresponding conversions of xylan to xylose were 96.9 ± 1.5%, 95.0 ± 2.2% and 76.1 ± 3.1%. Consistently, high sugar yield of 770–844 mg/g biomass was obtained for high-loading (10–16%, w/v) of OPEFB hydrolysis and sugar titer of 135.1 g/L was obtained for 16% (w/v) OPEFB loading at 96 h. In addition, MF6 enzymes alone performed equally well for high-loading OPEFB hydrolysis compared to the enzyme mixture of β-glucosidase from Aspergillus niger and cellulase from T. reesei Rut C30.  相似文献   

7.
Glucagon-like peptide-1 (GLP-1) has been proved to have effects of anti-hyperglycemia and β-cell preservation. However, it is still unclear whether there are differences between early and late GLP-1 intervention in type 2 diabetes mellitus (T2DM). We divided the mice into 5 groups: early treated group (n = 7, 8-week old, fasting glucose > 10 mmol/l), late treated group (n = 7, 10-week old, fasting glucose > 20 mmol/l), early control group (n = 7), late control group (n = 7) and wild type group (n = 7). Treated group was injected with liraglutide (a GLP-1 analog) 300 μg/kg bid for 4 weeks, while control group was given saline at the same time. The results showed that compared with control group, food intake and body weight gain were reduced in both early and late treated group (p < 0.05), and there was no significance between the two treated groups. Early liraglutide intervention showed better improvements in glucose control, acute insulin response to glucose (AIRg) and disposition index (before vs. after treatment, AIRg 1.01 ± 0.53 vs. 2.98 ± 0.63, disposition index 10.81 ± 0.89 vs. 27.4 ± 2.15) than late intervention (AIRg 0.99 ± 0.02 vs. 1.41 ± 0.32, disposition index 3.47 ± 0.38 vs. 6.43 ± 1.62, p = 0.001). The histopathology of the pancreas showed the estimated β-cell mass (BCM) was increased more in early treated group than that in late one (0.03 vs. 0.01 g). Expressions of the proliferation related genes PDX-1, MafA and GLP-1 receptor (GLP-1R) in early treated group were 1.81, 2.57 and 1.59 times as much as that in late treated group. In conclusion, early liraglutide intervention was better in glucose control, β-cell function improvement and β-cell mass preservation.  相似文献   

8.
We have previously demonstrated in human subjects who under euglycemic clamp conditions GLP-1(9–36)amide infusions inhibit endogenous glucose production without substantial insulinotropic effects. An earlier report indicates that GLP-1(9–36)amide is cleaved to a nonapeptide, GLP-1(28–36)amide and a pentapeptide GLP-1(32–36)amide (LVKGR amide). Here we study the effects of the pentapeptide on whole body glucose disposal during hyperglycemic clamp studies. Five dogs underwent indwelling catheterizations. Following recovery, the dogs underwent a 180 min hyperglycemic clamp (basal glucose +98 mg/dl) in a cross-over design. Saline or pentapeptide (30 pmol kg−1 min−1) was infused during the last 120 min after commencement of the hyperglycemic clamp in a primed continuous manner. During the last 30 min of the pentapeptide infusion, glucose utilization (M) significantly increased to 21.4 ± 2.9 mg kg−1 min−1compared to M of 14.3 ± 1.1 mg kg−1 min−1 during the saline infusion (P = 0.026, paired t-test; P = 0.062, Mann–Whitney U test). During this interval, no significant differences in insulin (26.6 ± 3.2 vs. 23.7 ± 2.5 μU/ml, P = NS) or glucagon secretion (34.0 ± 2.1 vs. 31.7 ± 1.8 pg/ml, P = NS) were observed. These findings demonstrate that under hyperglycemic clamp studies the pentapeptide modulates glucose metabolism by a stimulation of whole-body glucose disposal. Further, the findings suggest that the metabolic benefits previously observed during GLP-1(9–36)amide infusions in humans might be due, at least in part, to the metabolic effects of the pentapeptide that is cleaved from the pro-peptide, GLP-1(9–36)amide in the circulation.  相似文献   

9.
Targeted PEGylation of glucose oxidase at its glycosylation sites was investigated to determine the effect on enzymatic activity, as well as the bioconjugate's potential in an optical biosensing assay. Methoxy-poly(ethylene glycol)-hydrazide (4.5 kDa) was covalently coupled to periodate-oxidized glycosylation sites of glucose oxidase from Aspergillus niger. The bioconjugate was characterized using gel electrophoresis, liquid chromatography, mass spectrometry, and dynamic light scattering. Gel electrophoresis data showed that the PEGylation protocol resulted in a drastic increase (ca. 100 kDa) in the apparent molecular mass of the protein subunit, with complete conversion to the bioconjugate; liquid chromatography data corroborated this large increase in molecular size. Mass spectrometry data proved that the extent of PEGylation was six poly(ethylene glycol) chains per glucose oxidase dimer. Dynamic light scattering data indicated the absence of higher-order oligomers in the PEGylated GOx sample. To assess stability, enzymatic activity assays were performed in triplicate at multiple time points over the course of 29 days in the absence of glucose, as well as before and after exposure to 5% w/v glucose for 24 h. At a confidence level of 95%, the bioconjugate's performance was statistically equivalent to native glucose oxidase in terms of activity retention over the 29 day time period, as well as following the 24 h glucose exposure. Finally, the bioconjugate was entrapped within a poly(2-hydroxyethyl methacrylate) hydrogel containing an oxygen-sensitive phosphor, and the construct was shown to respond approximately linearly with a 220 ± 73% signal change (n = 4, 95% confidence interval) over the physiologically-relevant glucose range (i.e., 0–400 mg/dL); to our knowledge, this represents the first demonstration of PEGylated glucose oxidase incorporated into an optical biosensing assay.  相似文献   

10.
Beam hardening filters have long been employed in X-ray Computed Tomography (CT) to preferentially absorb soft and low-energy X-rays having no or little contribution to image formation, thus allowing the reduction of patient dose and beam hardening artefacts. In this work, we studied the influence of additional copper (Cu) and aluminium (Al) flat filters on patient dose and image quality and seek an optimum filter thickness for the GE LightSpeed VCT 64-slice CT scanner using experimental phantom measurements. Different thicknesses of Cu and Al filters (0.5–1.6 mm Cu, 0.5–4 mm Al) were installed on the scanner’s collimator. A planar phantom consisting of 13 slabs of Cu having different thicknesses was designed and scanned to assess the impact of beam filtration on contrast in the intensity domain (CT detector’s output). To assess image contrast and image noise, a cylindrical phantom consisting of a polyethylene cylinder having 16 holes filled with different concentrations of K2HPO4 solution mimicking different tissue types was used. The GE performance and the standard head CT dose index (CTDI) phantoms were also used to assess image resolution characterized by the modulation transfer function (MTF) and patient dose defined by the weighted CTDI. A 100 mm pencil ionization chamber was used for CTDI measurement. Finally, an optimum filter thickness was determined from an objective figure of merit (FOM) metric. The results show that the contrast is somewhat compromised with filter thickness in both the planar and cylindrical phantoms. The contrast of the K2HPO4 solutions in the cylindrical phantom was degraded by up to 10% for a 0.68 mm Cu filter and 6% for a 4.14 mm Al filter. It was shown that additional filters increase image noise which impaired the detectability of low density K2HPO4 solutions. It was found that with a 0.48 mm Cu filter the 50% MTF value is shifted by about 0.77 lp/cm compared to the case where the filter is not used. An added Cu filter with approximately 0.5 mm thickness accounts for 50% reduction in radiation-absorbed dose as measured by the weighted CTDI. The FOM results indicate that with an additional filter of 0.5 mm Cu or minimum 4 mm Al, a good compromise between image quality and patient dose is achieved for CT images acquired at tube voltages of 120 and 140 kVp. The results seem to indicate that an optimum filter for high kVp acquisitions, routinely used in cardiovascular imaging, should be 0.5 mm copper or 4 mm aluminium minimum.  相似文献   

11.
PurposeThe aim of the present investigation was to evaluate the dosimetric variation regarding the analytical anisotropic algorithm (AAA) relative to other algorithms in lung stereotactic body radiation therapy (SBRT). We conducted a multi-institutional study involving six institutions using a secondary check program and compared the AAA to the Acuros XB (AXB) in two institutions.MethodsAll lung SBRT plans (128 patients) were generated using the AAA, pencil beam convolution with the Batho (PBC-B) and adaptive convolve (AC). All institutions used the same secondary check program (simple MU analysis [SMU]) implemented by a Clarkson-based dose calculation algorithm. Measurement was performed in a heterogeneous phantom to compare doses using the three different algorithms and the SMU for the measurements. A retrospective analysis was performed to compute the confidence limit (CL; mean ± 2SD) for the dose deviation between the AAA, PBC, AC and SMU. The variations between the AAA and AXB were evaluated in two institutions, then the CL was acquired.ResultsIn comparing the measurements, the AAA showed the largest systematic dose error (3%). In calculation comparisons, the CLs of the dose deviation were 8.7 ± 9.9% (AAA), 4.2 ± 3.9% (PBC-B) and 5.7 ± 4.9% (AC). The CLs of the dose deviation between the AXB and the AAA were 1.8 ± 1.5% and −0.1 ± 4.4%, respectively, in the two institutions.ConclusionsThe CL of the AAA showed much larger variation than the other algorithms. Relative to the AXB, larger systematic and random deviations still appeared. Thus, care should be taken in the use of AAA for lung SBRT.  相似文献   

12.
The main objective of this study was to determine the treatment capacity of well-mineralized peat in vertical and horizontal flow filters designed to reduce phosphorus, nitrogen and organic matter in municipal wastewater from the town of Tapa and landfill leachate in Väätsa, Estonia. Two identically designed onsite experiments were conducted using the following filter systems: (a) a vertical flow (VF) peat filter, (b) a vertical flow peat/ash sediment filter (both materials in equal volumes) followed by a horizontal flow (HF) peat filter. Sphagnum peat and hydrated oil-shale ash (ash sediment) was used. In our experiments, one treated municipal wastewater over 6 months and another treated landfill leachate over 12 months. In both cases, effluent from a conventional treatment (aerated activated sludge treatment) plant was used. The median value of total phosphorus (TP) concentration in Väätsa landfill leachate was 3.4 mg P L?1 and in municipal wastewater from Tapa 4.9 mg P L?1. The reduction of TP in VF peat filters during the first 6 months was 58% and 63%, and in peat/ash sediment filters 94% and 67% for the Tapa experiment and the Väätsa experiment, respectively. Both experiments demonstrated that the P-removal efficiency in VF peat filters begins to decrease after 6 months of operation. The purification efficiency in HF filters fluctuated, and no significant removal of TP was found. In the removal of organic matter (BOD, COD values) and nitrogen, the best results were obtained in VF peat filters.  相似文献   

13.
14.
Background and objectivePatients with type 1 diabetes (T1DM) treated with continuous subcutaneous insulin infusion (CSII) have available several specific features of these devices. The aim of this study was to evaluate the relationship between real use of them and the degree of glycemic control in patients using this therapy.Patients and methodsForty-four T1DM patients on CSII therapy with or without real-time continuous glucose monitoring (CGM) were included. Data from 14 consecutive days were retrospectively collected using the therapy management software CareLink Personal/Pro® and HbA1c measurement performed at that period. The relationship between the frequency of usie of specific features of insulin pumps (non-sensor augmented or sensor-augmented) and glycemic control was analyzed.ResultsMean HbA1c in the group was 7.5 ± .8%. Mean daily number of boluses administered was 5.1 ± 1.8, with 75.4% of them being bolus wizards (BW). Daily number of boluses was significantly greater in patients with HbA1c < 7.5% than in those with HbA1c > 7.5% (5.3 ± 1.6 vs. 4.3 ± 1.6, P = .056). There was a trend to greater use of BW in patients with better control (82.8 ± 21.4% vs. 69.9 ± 29.1%, P = .106). HbA1c was lower in patients using CGM (n = 8) as compared to those not using sensor-augmented pumps (7.6 ± .8 vs 7.1 ± .7, P = .067), but the difference was not statistically significant.ConclusionsMore frequent use of BW appears to be associated to better metabolic control in patients with T1DM using pump therapy. In standard clinical practice, augmentation of insulin pump with CGM may be associated to improved glycemic control.  相似文献   

15.
We examined glucose 6-phosphate dehydrogenase (G6PD) production by fed-batch cultivation, using a recombinant strain of Saccharomyces cerevisiae W303-181 overexpressing this enzyme. The cultivations were carried out in a 3 L fermenter at pH 5.7, 30 °C, 2.0 vvm aeration, 200 rpm agitation and an inoculum concentration of 1.0 g/L. The volume of the culture medium in the fed-batch process varied from 1.333 to 2.0 L, due to the addition of 15.0 g/L glucose solution during 5 h. Different feeding rates were studied (exponentially increasing and decreasing feeding rates), and the feeding profile was determined by values of the parameter K (time constant), namely: 0.2, 0.5 and 0.8 h−1. The best enzyme production (847 U/L) was obtained with an exponentially increasing feeding rate and K = 0.2 h−1. The results attained also showed that this process is promising for G6PD production.  相似文献   

16.
17.
The importance of the region, as opposed to the length, of small intestine exposed to glucose in determining the secretion of the incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) remains unclear. We sought to compare the glycemic, insulinemic and incretin responses to glucose administered to the proximal (12–60 cm beyond the pylorus), or more distal ( > 70 cm beyond the pylorus) small intestine, or both. 10 healthy subjects (9M,1F; aged 70.3 ± 1.4 years) underwent infusion of glucose via a catheter into the proximal (glucose proximally; GP), or distal (glucose distally; GD) small intestine, or both (GPD), on three separate days in a randomised fashion. Blood glucose, serum insulin and plasma GLP-1, GIP and CCK responses were assessed. The iAUC for blood glucose was greater in response to GPD than GP (P < 0.05), with no difference between GD and GP. GP was associated with minimal GLP-1 response (P = 0.05), but substantial increases in GIP, CCK and insulin (P < 0.001 for all). GPD and GD both stimulated GLP-1, GIP, CCK and insulin (P < 0.001 for all). Compared to GP, GPD induced greater GLP-1, GIP and CCK responses (P < 0.05 for all). Compared with GPD, GD was associated with greater GLP-1 (P < 0.05), but reduced GIP and CCK (P < 0.05 for both), responses. We conclude that exposure of glucose to the distal small intestine appears necessary for substantial GLP-1 secretion, while exposure of both the proximal and distal small intestine result in substantial secretion of GIP.  相似文献   

18.
IntroductionWhen ictal and interictal brain SPECT are reconstructed with filtered backprojection (FBP), the noise level of subtraction images is frequently high and requires the use of thresholding methods. The aim of this study was to compare the subtraction images for cerebral SPECT reconstructed either with FBP or with a 3D iterative reconstruction method (OSEM-3D).Material and methodsAfter optimisation of the reconstruction parameters on phantom, the subtraction SPECT images, which were obtained with FBP or with OSEM-3D and coregistered with MRI images, were analyzed in 15 patients with refractory temporal epilepsy.ResultsOn phantom and with the constrain of high enough spatial resolution (full width at half of maximum for a punctual source less than or equal to 11 mm) were reached using: (i) a Butterworth filter with a cut-off frequency of 0.4 Nyquist at order 6 for FBP and (ii) five iterations, 16 subsets and a 9 mm gaussian filter for OSEM-3D. On the subtraction images, which were obtained with these optimal parameters, the temporal foci from patients were smaller with OSEM-3D than with FBP (11 ± 6 cm3 versus 17 ± 10 cm3, P = 0.02), mean voxel activities were equivalent between the two methods within temporal foci (6.30 ± 3.13 counts versus 6.34 ± 4.93 counts) but these activities were dramatically reduced by OSEM-3D within background regions (0.02 ± 0.02 counts versus 0.19 ± 0.12 counts, P < 0.001).ConclusionFor the ictal–interictal subtraction SPECT images, which are obtained in patients with refractory temporal epilepsy, the use of an optimized OSEM-3D method leads to dramatically reduce the volume of temporal foci, as well as the background noise level, two properties that are likely to facilitate the detection and localisation of epilepsy foci.  相似文献   

19.
20.
A linear encoder measuring vertical displacement during the heel-rise endurance test (HRET) enables the assessment of work and maximum height in addition to the traditional repetitions measure. We aimed to compare the test-retest reliability and agreement of these three outcome measures. Thirty-eight healthy participants (20 females, 18 males) performed the HRET on two occasions separated by a minimum of seven days. Reliability was assessed by the intraclass correlation coefficient (ICC) and agreement by a range of measures including the standard error of measurement (SEM), coefficient of variation (CV), and 95% limits of agreement (LoA). Reliability for repetitions (ICC = 0.77 (0.66, 0.85)) was equivalent to work (ICC = 0.84 (95% CI 0.76, 0.89)) and maximum height (ICC = 0.85 (0.77, 0.90)). Agreement for repetitions (SEM = 6.7 (5.8, 7.9); CV = 13.9% (11.9, 16.8%); LoA = −1.9 ± 37.2%) was equivalent to work (SEM = 419 J (361, 499 J); CV = 13.1% (11.2, 15.8%); LoA = 0.1 ± 34.8%) with maximum height superior (SEM = 0.8 cm (0.6, 1.0 cm); CV = 6.6% (5.7, 7.9%); LoA = 1.3 ± 17.1%). Work and maximum height demonstrated acceptable reliability and agreement that was at least equivalent to the traditional repetitions measure.  相似文献   

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