共查询到20条相似文献,搜索用时 515 毫秒
1.
Escobar Jose M. Rane Kishore D. Cheryan Munir 《Applied biochemistry and biotechnology》2001,91(1-9):283-296
Pilot plant trials were conducted in a corn wet mill with a 7000-L membrane recycle bioreactor (MRB) that integrated ceramic
microfiltration membranes in a semi-closed loop configuration with a stirred-tank reactor. Residence times of 7.5–10 h with
ethanol outputs of 10–11.5% (v/v) were obtained when the cell concentration was 60–100 g/L drywt of yeast, equivalent to about
109−1010 cells/mL. The performance of the membrane was dependent on the startup mode and pressure management techniques. A steady
flux of 70 L/(m2·h) could be maintained for several days before cleaning was necessary. The benefits of the MRB include better productivity;
a clear productstream containing no particulates or yeast cells, which should improve subsequent stripping and distillation
operations; and substantially reduced stillage handling. The capital cost of the MRB is $21–$34/(m3·yr) ($0.08–$0.13/[gal·yr]) of ethanol capacity. Operating cost, including depreciation, energy, membrane replacement, maintenance,
labor, and cleaning, is $4.5–9/m3 ($0.017–$0.034/gal) of ethanol. 相似文献
2.
A shear-enhanced, cross-flow ultrafiltration module was used to separate cells and proteins from the fermentation broth. Three
(fermented) media were studied: rich medium, rich medium with hydrolytic enzymes added after fermentation, and wheat flour
hydrolysate. To find a membrane with as high a flux as possible, but still capable of separating cells and proteins from the
lactic acid containing broth, the performance of three hydrophilic membranes of varying cutoffs (10,000, 20,000, and 30,000)
and one hydrophobic membrane (cutoff 25,000) was investigated. The proteins produced by the lactic acid bacteria during fermentation
and the hydrolytic proteins were retained by the hydrophilic membrane with a cutoff of 20,000, whereas wheat flour proteins
were detected in the permeate. In the permeates from the hydrophobic membrane (cutoff 25,000), almost no proteins were detected.
The flux of the whole-wheat flour hydrolysate was significantly lower than that of rich medium, for both the hydrophilic and
the hydrophobic membranes. The flux was, in all cases, higher for the hydrophilic membrane (12–85 L/[m2·h], depending, on which medium was treated) than for the hydrophobic one (8–45 L/[m2·h]), even though the nominal cutoffs of the hydrophobic and hydrophilic membranes were almost the same. However, the difference
in flux was smaller when the whole-wheat flour hydrolysate was processed (12 vs 8 L/[m2·h]) than when the rich medium was processed (85 vs 45 L/[m2·h]). Protein retention was higher for the hydrophobic membrane than for the hydrophilic membrane (cutoff 20,000) owing to
blocking of the pores by proteins adsorbed on to the hydrophobic membrane surface. 相似文献
3.
Matioli Graciette Zanin Gisella M. De Moraes Flávio F. 《Applied biochemistry and biotechnology》2001,91(1-9):643-654
The enzyme cyclod extringly cosyltransferase (CGTase), EC2.4.1.19, which produces cyclodextrins (CDs) from starch, was obtained
from Bacillus firmus strain no. 37 isolated from Brazilian soil and characterized in the soluble form using as substrate 100 g/L of maltodextrin
in 0.05 M Tris-HCl buffer, 5 mM CaCl2, and appropriate buffers. Enzymatic activity and its activation energy were determined as a function of temperature and pH.
The activation energy for the production of β- and γ-CD was 7.5 and 9.9 kcal/mol, respectively. The energy of deactivation
was 39 kcal/mol. The enzyme showed little thermal deactivation in the temperature range of 35–60°C, and Arrhenius-type equations
were obtained for calculating the activity, deactivation, and half-life as a function of temperature. The molecular weight
of the enzyme was determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis, giving 77.6k Da. Results for CGTase
activity as a function of temperature gave maximal activity for the production of β-CD at 65°C, pH 6.0, and 7 1.5 mmol of
β-CD/(min·mg of protein), whereas for γ-CD it was 9.1 m mol of γ-CD/(min·mg of protein) at 70°C and pH 8.0. For long contact
times, the bestuse of the enzymatic activity occurs at 60°C oratalower temperature, and the reaction pH may be selected to
increase the vield of a desired CD. 相似文献
4.
The batch culture of a newly isolated strain of a green microalga, Chlorella sorokiniana, was carried out using a conical helical tubular photobioreactor. The isolate was capable of good growth at 40°C under an
airstream enriched with 10% CO2. The maximum photosynthetic productivity was 34.4g of dry biomass/(m2 of installation area · d) (12-h light/12-h dark cycle) when the cells were illuminated with an average photosynthetic photon
flux density (photosynthetically active radiation ([PAR] 400–700 nm) simulating the outdoors in central Japan (0.980 mmol
photons/[m2·s]). This corresponded to a photosynthetic efficiency of 8.67% (PAR), which was defined as the percentage of the light energy
recovered as biomass (394 kJ/[reactor·d]) to the total light energy received (4545 kJ/[reactor·d]). A similarly high photosynthetic
efficiency (8.12% [PAR]) was also attained in the combined presence of 10% CO2, 100 ppm of NO, and 25 ppm of SO2. Moreover, good photosynthetic productivity was also obtained under high temperature and high light intensity conditions
(maximum temperature, 46.5°C; 1.737 mmol photons/[m2·s]), when simulating the strong irradiance of the midday summer sun. This strain thus appears well suited for practical application
for converting CO2 present in the stack gases emitted by thermal power plants and should be feasible even during the hot summer weather. 相似文献
5.
N. E. Bores M. K. Schultz J. M. Rankin A. J. Denton G. F. Payne R. E. Steiner S. P. LaMont S. B. Ortiz 《Journal of Radioanalytical and Nuclear Chemistry》2008,276(2):513-518
The Intercomparison Studies Program (ISP) at the Oak Ridge National Laboratory (ORNL, Oak Ridge, TN, USA) provides natural-matrix
urine quality-assurance/quality-control (QA/QC) samples to radiobioassay analysis laboratories. In 2003, a single laboratory
(Los Alamos National Laboratory LANL, Los Alamos NM USA) requested a change in the test-samples provided previously by the
ISP. The change was requested to evaluate measurement performance for analyses conducted using thermal-ionization mass spectrometry
(TIMS). Radionuclides included 239Pu at two activity levels (75–150 μBq·sample−1 and 1200–1600 μBq·sample−1) and 238Pu (3700–7400 μBq·sample−1). In addition, 240Pu was added to the samples so that the 239+240Pu specific activity was 3700–7400 μBq·sample−1. In this paper, the results of testing during the period May, 2003 through September, 2005 are presented and discussed. 相似文献
6.
将3-氨丙基三乙氧基硅烷(APTES)引入到T型分子筛膜表面,用以修饰多晶膜合成过程中产生的缺陷。X射线衍射、场发射扫描电子显微镜、X射线光电子能谱和FT-IR等方法的表征结果显示,APTES通过“键合”的形式被成功地修饰到膜表面上。APTES层起到2个作用:一是提高膜的亲水性;二是减少膜层的缺陷。将修饰后的膜应用在348 K、90%的异丙醇水溶液的脱水时,该膜表现出比较高的分离因子和通量。该方法重复性良好,5个修饰后的膜样品的选择性平均增加了大约8倍(从359±23增加到2 934±183),而渗透通量仅仅从(3.52±0.10) kg·m-2·h-1降低到(3.06±0.14) kg·m-2·h-1(减少13.07%)。在363 K下,修饰的膜经过100 h的连续测试,膜渗透测得的水含量均可达到99.50%以上,表明修饰后的膜性能较稳定。 相似文献
7.
C. García-Verdugo-Caso J. L. Hidalgo-Hidalgo-de-Cisneros I. Naranjo-Rodríguez D. Bellido-Milla 《Analytical and bioanalytical chemistry》2001,370(4):393-398
A new quartz crystal microbalance sensor is developed to determine formic acid at low concentrations. Four previously selected
polymers with acid–base characteristics were tested as possible coatings. Polyoxyethylene bis [amine] presented the best results.
The sensor is rapid, sensitive [0.67 Hz/(mg/m3)], and reversible at low concentrations. The detection limit for formic acid (7.2 mg/m3) is comparable with the short term exposure limit and the threshold limit values. It presents a fast mechanical response
to pressure changes, so that it can be quickly used in different environments and situations. The sensor also shows a good
stability in a temperature range typical of work atmospheres (16–36 °C). It has a wide linear range (7.2–911.2 mg/m3) and a long useful time. It is also applicable to other low molecular mass carboxylic acids such as acetic acid.
Received: 26 September 2000 / Revised: 8 February 2001 / Accepted: 12 February 2001 相似文献
8.
A fast non-destructive determination of fluorine in bone samples by thermal neutron activation analysis using19F(n, γ)20F reaction was developed. About 0.1–1 g samples is irradiated for 15 sec in TRIGA MARK II reactor at a thermal neutron flux
of 5·1011 n·cm−2·sec−1. After 15–25 sec cooling, the 1633 KeV20F activity (T=11.2 sec) is counted for 15 sec with a Ge(Li) spectrometer. A standard sample is prepared by mixing CaF2 and CaCO3 powders. The interference from23Na(n, α)20F is corrected by employing24Na 2754 KeV double escape peak activities in samples and the20F/24Na peak area ratio observed previously for pure Na2CO3 powder. The precision is 7% for a bone sample containing 1020 ppm F and the sensitivity is about 10 ppm F. 相似文献
9.
High-performance silicalite-1 membranes were synthesized on silica tubes by in-situ hydrothermal synthesis. By using the "solution-filling (SF)" method, the average flux of membranes with the SF method was improved by about 25% compared to that of the membranes without using the SF method; the flux and the separation factor of the membranes prepared with the SF method for an ethanol/water mixture at 60 ℃ were 0.99 kg/(m2·h) and 73, respectively. It was found that the membranes synthesized on silica tubes ex... 相似文献
10.
Xin-Liang Li Lars G. Ljungdahl Eduardo A. Ximenes Huizhong Chen Carlos R. Felix Michael A. Cotta Bruce S. Dien 《Applied biochemistry and biotechnology》2004,113(1-3):233-250
A β-glucosidase (BglA, EC 3.2.1.21) gene from the polycentric anaerobic fungus Orpinomyces PC-2 was cloned and sequenced. The enzyme containing 657 amino acid residues was homologous to certain animal, plant, and
bacterial β-glucosidases but lacked significant similarity to those from aerobic fungi. Neither cellulose- nor protein-binding
domains were found in BglA. When expressed in Saccharomyces cerevisiae, the enzyme was secreted in two forms with masses of about 110 kDa and also found in two forms associated with the yeast
cells. K
m
and V
max
values of the secreted BglA were 0.762 mM and 8.20 μmol/(min·mg), respectively, with p-nitrophenyl-β-d-glucopyranoside (pNPG) as the substrate and 0.310 mM and 6.45 μmol/(min·mg), respectively, for the hydrolysis of cellobiose. Glucose competitively inhibited the hydrolysis of
pNPG with a K
i
of 3.6 mM. β-Glucosidase significantly enhanced the conversion of cellulosic materials into glucose by Trichoderma reesei cellulase preparations, demonstrating its potential for use in biofuel and feedstock chemical production.
Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard
of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may be
suitable. 相似文献
11.
Organic microporous materials based on spiroketal and spirothioketal polymers were synthesized through 1,3-dioxol-forming
polymerization reaction between pentaerythritol or pentaerythritol tetrathiol and different types of cyclohexa-1,4-dione derivatives.
The structure of the prepared polymers was confirmed by NMR spectroscopy and molecular mass measurements. Nitrogen adsorption/desorption
isotherms of the prepared polymers show a large amount of nitrogen adsorbed at low relative pressure indicating microporosity.
These polymers have Brunauer Emmitt and Teller (BET) surface areas in the range from 492 (m2 g−1) to 685 (m2 g−1). The prepared polymers were found to be useful for pervaporation separation of methanol-toluene mixture with a separation
factor up to 12.5 and fluxes, varying between 6.7 × 10−3 kg/(m2 h) and 13.4 × 10−3 kg/(m2 h). 相似文献
12.
Chua Hong Li Xiang Z. Yu Peter H. F. Tam Chung Y. Huang Yu L. Yang Shang T. 《Applied biochemistry and biotechnology》2000,84(1-9):469-478
Biological processes have become popular for odor treatment. In this study, a novel fibrous bed bioreactor was applied for
treatment of odorous gas. The column reactor was packed with spirally wound fibrous sheet material on which a consortium of
microorganisms selected from activated sludge was immobilized. The first stage of this work comprised a preliminary study
that aimed at investigating the feasibility of the fibrous bed bioreactor for treatment of odorous volatile fatty acids (VFAs).
In this stage, the performance of a fibrous bed bioreactor at increasing mass loadings ranging from 9.7 to 104.2 g/(m3·h) was studied. VFA removal efficiencies above 90% were achieved at mass loadings up to 50.3 g/(m3·h). At a mass loading of 104.2 g/(m3·h), removal efficiency was found to be 87.7%. In the second stage of the work, the process was scaled up with design and
operational considerations, namely, packing medium, process condition, and configuration selections. A trickling biofilter
with synthetic fibrous packing medium was selected. It was operated under countercurrent flow of gas and liquid streams. The
effects of inlet concentration and empty bed retention time on bioreactor performance were studied. The bioreactor was effective
in treating odorous VFAs at mass loadings up to 32g/(m3·h), at which VFAs started to accumulate in the recirculation liquid, indicating that the biofilm was unable to degradeall
the VFAs introduced. Although VFAs accumulated in the liquid phase, the removal efficency remained above 99%, implying that
the biochemical reaction rate, rather than gas-to-liquid mass transfer rate, was the limiting factor of this process. The
bioreactor was stable for longterm operation; no clogging and degeneration of the packing medium was observed during the 4-mo
operation. 相似文献
13.
Wakayama Tatsuki Nakada Eiju Asada Yasuo Miyake Jun 《Applied biochemistry and biotechnology》2000,84(1-9):431-440
Hydrogen production by photosynthetic bacteria provides an efficient energy conversion method under low light intensity. However,
under strong illumination, such as midday sunlight, the efficiency drops. This prevents the method from being applied industrially.
To overcome this problem, we examined a method to thin out the excessive illumination. Light was given intermittently to reduce
the total energy flux. The on/off ratio was set at 1/1 throughout the study, so that the time average of the light energy
flux became half the continuous illumination. By keeping the time-average light flux constant (0.6 kW·m−2), the effects of the cycle period were examined in the range of hours to seconds. The hydrogen production rate was greatly
affected by the cycle period, but cell growth and substrate consumption rates remained almost constant. The 30-min light/dark
cycle (30 min on and 30 min off) provided the highest rate of hydrogen production (22 L·m−2·24 h−1). At the shorter cycles, the rate decreased except that there was a suboptimum at about 40 s. Under excessive light intensity
(1.2 kW·m−2), the light-to-hydrogen conversion efficiency was greatly enhanced. The hydrogen production rate during the 30-min cycle
was twice as high as during a 12-h cycle under the same conditions. 相似文献
14.
Aminzadeh S Naderi-Manesh H Khajeh K Naderi-Manesh M 《Applied biochemistry and biotechnology》2006,135(3):193-208
For the first time, a polygalacturonase from the culture broth of Tetracoccosporium sp. was isolated and incubated at 30°C in an orbital shaker at 160 rpm for 48h. The enzyme was purified by ammonium sulfate
precipitation and two-step ion-exchange chromatography and had an apparent molecular mass of 36 kDa, as shown by sodium dodecyl
sulfate (SDS)-polyacrylamide gel electrophoresis. Its optimum activity was at pH 4.3 and 40°C, and the K
m
and V
max values of this enzyme (for polygalacturonic acid) were 3.23 mg/mL and 0.15 μmol/min, respectively. Ag+, Co2+, EDTA, Tween-20, Tween-80, and Triton X-100 stimulated polygalacturonase activity whereas Al3+, Ba2+, Ca2+, Fe2+, Fe3+, Ni2+, Mg2+, Mn2+, and SDS inhibited it. In addition, iodoacetamide and iodoacetic acid did not inhibit enzyme activity at a concentration
of 1 mM, indicating that cysteine residues are not part of the catalytic site of polygalacturonase. We studied the kinetic properties
and thermal inactivation of polygalacturonase. This enzyme exhibited a t
1/2 of 63 min at 60°C and its specific activity, turnover number, and catalytic efficiency were 6.17 U/mg, 113.64 min−1, and 35.18 mL/(min·mg), respectively. The activation energy (ΔE
#) for heat inactivation was 5.341 kJ/mol, and the thermodynamic activation parameters ΔG
#, ΔH
#, and ΔS
# were also calculated, revealing a potential application for the industry. 相似文献
15.
Separation of an organics/water mixture was carried out by reverse osmosis using an α-alumina-supported MFI-type zeolite membrane. The organic rejection performance is strongly dependent on the ionic species and dynamic size of dissolved organics. The membrane showed high rejection efficiency for electrolytes such as pentanoic acid. An organic rejection of 96.5% with a water flux of 0.33 kg m−2 h−1 was obtained for 100 ppm pentanoic acid solution at an operation pressure of 2.76 MPa. For non-electrolyte organics, separation efficiency is governed by the molecular dynamic size; the organics with larger molecular dynamic size show higher separation efficiency. The zeolite membrane gives an organic rejection of 99.5% and 17% for 100 ppm toluene and 100 ppm ethanol, respectively, with a water flux of 0.03 kg m−2 h−1, 0.31 kg m−2 h−1 at an operation pressure of 2.76 MPa. It was observed that organic rejection and water flux were affected by the organic concentration. As pentanoic acid concentration increased from 100 ppm to 500 ppm, both organic rejection and water flux decreased slightly. 相似文献
16.
Pereira Ernandes B. De Castro Heizir F. De Moraes Flávio F. Zanin Gisella M. 《Applied biochemistry and biotechnology》2001,91(1-9):739-752
The search for an in expensive support has motivated our group to undertake this work dealing with the use of chitosan as
matrix for immobilizing lipase. In addition to its low cost, chitosan has several advantages for use as a support, including
its lack of toxicity and chemical reactivity, allowing easy fixation of enzymes. In this article, we describe the immobilization
of Canada rugosa lipase onto porous chitosan beads for the enzymatic hydrolysis of oliveoil. The binding of the lipase onto the support was
performed by physicalad sorption using hexane as the dispersion medium. A comparativestudy between free and immobilized lipase
was conducted in terms of pH, temperature, and thermal stability. A slightly lower value for optimum pH (6.0) was found for
the immobilized form in comparison with that attained for the soluble lipase (7.0). The optimum reaction temperature shifted
from 37°C for the free lipase to 50°C for the chitosan lipase. The patterns of heat stability indicated that the immobilization
process tends to stabilize the enzyme. The half-life of the soluble free lipase at 55°C was equal to 0.71 h (K
d=0.98 h−1), whereas for the immobilized lipase it was 1.10 h (K
d=0.63 h−1). Kinetics was tested at 37°C following the hydrolysis of olive oil and obeys the Michaelis-Menten type of rate equation.
The K
m was 0.15 mM and the V
max was 51 μmol/(min·mg), which were lower than for free lipase, suggesting that the apparent affinity toward the substrate changes
and that the activity of the immobilized lipase decreases during the course of immobilization. 相似文献
17.
In situ
developments of platelike spodumene–diopside grains were obtained by
controlled devitrification of the complex system Li2O–CaO–MgO–Al2O3–SiO2 glass. The crystallization mechanisms
of spodumene–diopside glass were measured by isothermal and non-isothermal
processes using classical and differential thermal analysis techniques. The
Avrami constant n was 2.0–2.1, indicating
two-dimensional crystal growth and platelike grains. The crystalline phases
precipitated first were high-quartzs.s., then transformed
to β-spodumene and diopside. The Flexural strength, fracture toughness
and thermal shock resistance (in 20°C water) increased from 145 MPa, 1.3
MPa m1/2, 800°C (pure spodumene) to 197 MPa,
2.9 MPa m1/2 and 920°C (spodumene–diopside)
with low thermal expansion coefficient (from 3∼9·10–7
to 11.8·10–7 K–1).
This mean in situ developments of platelike spodumene–diopside grains
reinforced the low thermal expansion coefficient glass-ceramics. 相似文献
18.
High-performance silicalite-1 membranes were successfully synthesized on novel porous silica tubes by two-step in-situ hydrothermal synthesis.The flux and separation factor towards ethanol/water mix- ture at 60℃were 0.56 kg/(m2·h)and 84,respectively.The as-synthesized silicalite-1 membranes were characterized by scanning electron microscopy(SEM).The influence of different synthesis conditions on the separation performance of the silicalite-1 membranes was investigated.It was found that the average flux of silicalite-1 membranes was improved by about 26?ter filling the silica tubes with mixed solution containing glycerol and water.After calcinating at 400℃for 5 h repeatedly,membrane synthesized on silica tube still showed high pervaporation performance towards ethanol/water mixture even at a calcination rate of 4℃/min,which suggested that silica support was more suitable for pre- paring high-performance silicalite-1 membranes. 相似文献
19.
M. A. Motaleb M. T. El-Kolaly A. B. Ibrahim A. Abd El-Bary 《Journal of Radioanalytical and Nuclear Chemistry》2011,289(1):57-65
The aim of this work is the development of new radiopharmaceuticals for imaging infection and inflammation in human. Gatifloxacin
(fluoroquinolone derivative) and cefepime (cephalosporine derivative) are antibiotics used to treat bacterial infections were
investigated to label with one of the most important radioactive isotopes (technetium-99m). The reaction parameters that affect
the labeling yield such as substrate concentration, stannous chloride dihydrate concentration, pH of the reaction mixture,
and reaction time were studied to optimize the labeling conditions. Maximum radiochemical yield of 99mTc–gatifloxacin (90 ± 1.8%) complex was obtained by using 50 μg SnCl2·2H2O and 2.5 mg gatifloxacin at pH 10 while 99mTc–cefepime was prepared at pH 8 with a maximum radiochemical yield of 98 ± 1.4% by adding 99mTc to 5 mg cefepime in the presence of 50 μg SnCl2·2H2O. Biological distribution of 99mTc–gatifloxacin and 99mTc–cefepime was carried out in experimentally induced infection rats, in the left thigh, using Escherichia coli. Both thighs of the rats were dissected and counted and the ratio of bacterial infected thigh/contralateral thigh was then
evaluated. T/NT for both 99mTc–gatifloxacin and 99mTc–cefepime was found to be 4.5 ± 0.3 and 8.4 ± 0.1, respectively, which was higher than that of the commercially available
99mTc–ciprofloxacin. The abscess to normal muscle ratio indicated that 99mTc–cefepime could be used for infection imaging. Besides, in vitro studies showed that 99mTc–cefepime can differentiate between bacterial infection and sterile inflammation. 相似文献
20.
Tatiana P. Mosolova Sergey V. Kalyuzhnyi Sergey D. Varfolomeyev Galina A. Velikodvorskaya 《Applied biochemistry and biotechnology》1993,42(1):9-18
Endoglucanase 5 (EG5) has been isolated from the strain ofE. coli TGI harboring recombinant plasmid pCU108, which contains thecel5 gene ofC. thermocellum. The enzyme has been produced with 98-fold purification and a final yield of 27% by using subsequent twofold high performance ion-exchange chromatography on Mono Q and high performance chromatofocusing on Mono P. The protein has a mol mass of 35 kDa and includes 3 multiple forms with pI 4.4–4.8 as evidenced by analytical gel isoelectrofocusing. EG5 cleaves CMC (Km = 0.097 g/L, Vmax = 8.2 mg/min·mg of protein), amorphous cellulose, xylan, lichenan as a substrate with an optimum temperature of 80?C and pH 6.0 and Avicel (Km = 18.2 g/L, Vmax = 0.035 mg/min·mg of protein) with an optimum temperature of 60?C and pH 6.O. Cellobiose in concentrations up to 200 Μg/mL do not inhibit the hydrolysis of CMC by EG5, but 10–30 Μg/mL of glucose significantly decrease the activity of this enzyme. The stimulating role of calcium chloride and concentration of protein in the system has been demonstrated for Avicel hydrolysis by EG5. 相似文献