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1.
Owen S. Jeong B. C. Poole P. S. Macaskie L. E. 《Applied biochemistry and biotechnology》1992,(1):693-707
Tributyl phosphate (TBP), a plasticizer and solvent, is used in nuclear fuel reprocessing, generating TBP wastes laden with
residual uranium. ACitrobacter sp. accumulated heavy metals via a phosphohydrolase(s) that precipitated metals with inorganic phosphate liberated from an
organic phosphate “donor” molecule (TBP). Mutant analysis suggested that TBP hydrolysis was not attributable to a previously
documented acid phosphatase (monoesterase). Purified monoesterase had little activity against phospho di- and triesters, had
no requirement for Mg2+ or Mn2+, and was EDTA-resistant. Conversely, TBP cleavage by immobilized cells was enhanced by Mg2+, and ininhibited by Mn2+ and EDTA. A separate phosphotri/diesterase was implicated. 相似文献
2.
Cruz A. J. G. Araujo M. L. G. C. Giordano R. C. Hokka C. O. 《Applied biochemistry and biotechnology》1998,(1):579-592
Cephalosporin C production process withCephalosporium acremonium ATCC 48272 in synthetic medium was investigated and the experimental results allowed the development of a mathematical model
describing the process behavior. The model was able to explain fairly well the diauxic phenomenon, higher growth rate during
the glucose-consumption phase, and the production occurring only in the sucrose-consumption phase.
Moreover, the process was simulated utilizing the neural-networks technique. Two feed-forward neural-networks with one hidden
layer were employed. Both models, phenomenological and neural-networks based, satisfactorily describe the bioprocess. The
difficulties in determining kinetic parameters are avoided when neural networks are utilized. 相似文献
3.
Stenberg Kerstin Tengborg Charlotte Galbe Mats Zacchi Guido Palmqvist Eva Hahn-Hägerdal Bärbel 《Applied biochemistry and biotechnology》1998,(1):697-708
In ethanol production from lignocellulose by enzymatic hydrolysis and fermentation, it is desirable to minimize addition of
fresh-water and waste-water streams, which leads to an accumulation of substances in the process. This study shows that the
amount of fresh water used and the amount of waste water thereby produced in the production of fuel ethanol from softwood,
can be reduced to a large extent by recycling of either the stillage stream or part of the liquid stream from the fermenter.
A reduction in fresh-water demand of more than 50%, from 3 kg/kg dry raw material to 1.5 kg/kg dry raw material was obtained
without any negative effects on either hydrolysis or fermentation. A further decrease in the amount of fresh water, to one-fourth
of what was used without recycling of process streams, resulted in a considerable decrease in the ethanol productivity and
a slight decrease in the ethanol yield 相似文献
4.
Azmi Telefoncu Erhan Dlnckaya Klaus D. Vorlop 《Applied biochemistry and biotechnology》1990,26(3):311-317
Pancreatic lipase (EC 3.1.1.3) was immobilized by entrapping in a commercial preparation of acrylic/methacrylic acid ester-based copolymer (Eudragit E 30 D). The activity of the immobilized lipase beads with a diameter of 1.5-2.0 mm was found to be lower than that of the free lipase. The optimum pH was shifted to the alkaline region and the thermal stability increased, whereas the optimum temperature level remained unchanged. The most important reason for the decreased activity was diffusion limitations. The diffusion of the substrate and products became more pronounced, and lipolytic activity increased upon addition of n-hexane into the reaction medium. The storage and operational stabilities of the immobilized lipase were investigated, and both characteristics were found to be increased when compared to the free enzyme. Furthermore, mechanical or magnetic stirring during the operation were found to have no influence on the carrier-matrix as determined by nephelometric measurements. 相似文献
5.
A. L. Simonian E. I. Rainina V. I. Lozinsky I. E. Badalian G. E. Khachatrian S. Sh. Tatikian T. A. Makhlis S. D. Varfolomeyev 《Applied biochemistry and biotechnology》1992,36(3):199-210
A biosensor to quantify L-proline within 10(-5)-10(-3) mole/L concentration is described. Immobilized Pseudomonas sp. cells grown in a medium containing L-proline as the only source of carbon and nitrogen were used to create the biosensor. The cells oxidized L-proline specifically consuming O2 and did not react with other amino acids and sugars. The change in oxygen concentration was detected with a Clark oxygen membrane electrode. The cells were immobilized by entrapment in polyvinyl alcohol (PVA) cryogel. The resultant biocatalyst had a high mechanical strength and retained its L-proline-oxidizing ability for at least two months. 相似文献
6.
Ackerson M. D. Johnson N. L. Le M. Clausen E. C. Gaddy J. L. 《Applied biochemistry and biotechnology》1990,(1):913-928
Recently, several microorganisms have been shown to be capable of directly solubilizing low-rank coals. This bioextract has
a high molecular weight and is water soluble, but is not useful as a liquid fuel. This paper presents the results of studies
to biologically solubilize coal and convert the solubilized coal into more useful compounds. Preliminary experiments have
been conducted to isolate cultures for the serial biological conversion of coal into liquid fuels. Coal particles have been
solubilized employing an isolate from the surface of Arkansas lignite. Natural inocula, such as sheep rumen and sewage sludge,
are then employed in developing cultures for converting the bioextract into fuels. This paper presents preliminary results
of experiments in coal solubilization and bioextract conversion. 相似文献
7.
Amyloglucosidase from Novo (Copenhagen, Denmark) was immobilized in controlled pore silica particles with the silane-glutaraldehyde
covalent method. Thermal stability of the free and immobilized enzyme (IE) was determined with 30% (w/v) α-amylase liquefied
cassava starch, pH 4.5, temperatures from 35 to 75°C. Free amyloglucosidase maintained its activity practically constant for
240 min and temperatures up to 50°C. The IE has shown higher stability retaining its activity for the same period up to 60°C.
Half-life for free enzyme was 20.6, 6.44, 2.07, 0.69, and 0.24 h for 55, 60, 65, 70, and 75°C, respectively, whereas the IE
at the same temperatures had half-lives of 116.4, 30.88, 8.52, 2.44, and 0.73 h. The energy of thermal deactivation was thus
50.6 and 57.6 kcal/mol, respectively for the free and IE, confirming stabilization by immobilization. 相似文献
8.
Immobilization ofRhizopus arrhizus mycelium improved fumaric acid production. The optimum conditions for fumaric acid production with immobilized cells were
investigated using a statistical experimental design. Substrate concentration, carbon:nitrogen ratio, and residence time were
chosen as independent variables. In the repeated batch shake flask fermentation, the fumaric acid yield from xylose was as
much as 3.5 times higher with immobilized mycelium than with free mycelium. Polyurethane foam cubes, in this case, gave better
results than nylon net cubes as a carrier. 相似文献
9.
L-Malate was produced from fumarate by using immobilized Saccharomyces cerevisiae cells entrapped in polyacrylamide. This preparation performed better when pretreated with malonate. Under the experimental conditions described here, succinate was not detected as a by-product of the reaction, as had been reported for other microorganisms. 相似文献
10.
Tucker M. P. Farmer J. D. Keller F. A. Schell D. J. Nguyan Q. A. 《Applied biochemistry and biotechnology》1998,(1):25-35
Single-stage cocurrent dilute acid pretreatments were carried out on yellow poplar (Liriodendron tulipifera) sawdust using an as-installed and short residence time modified pilot-scale Sunds hydrolyzer and a 4-L bench-scale NREL
digester (steam explosion reactor). Pretreatment conditions for the Sunds hydrolyzer, installed in the NREL process development
unit (PDU), which operates at 1 t/d (bone-dry t) feed rate, spanned the temperature range of 160 – 210°C, 0.1 – 1.0% (w/w)
sulfuric acid, and 4-10-min residence times. The batch pretreatments of yellow poplar sawdust in the bench-scale digester
were carried out at 210 and 230°C, 0.26% (w/w) sulfuric acid, and 1-, 3-, and 4-min residence times. The dilute acid prehydrolysis
solubilized more than 90% of the hemicellulose, and increased the enzymatic digestibility of the cellulose that remained in
the solids. Compositional analysis of the pretreated solids and liquors and mass balance data show that the two pretreatment
devices had similar pretreatment performance. 相似文献
11.
The potential market for lactic acid as the feedstock for biodegradable polymers, oxygenated chemicals, and specialty chemicals
is significant. L-lactic acid is often the desired enantiomer for such applications. However, stereospecific lactobacilli
do not metabolize starch efficiently. In this work, Argonne researchers have developed a process to convert starchy feedstocks
into L-lactic acid. The processing steps include starch recovery, continuous liquefaction, and simultaneous saccharification
and fermentation. Over 100 g/L of lactic acid was produced in less than 48 h. The optical purity of the product was greater
than 95%. This process has potential economical advantages over the conventional process. 相似文献
12.
de Castro Heizir F. Napoleão Diovana A. S. Oliveira Pedro C. 《Applied biochemistry and biotechnology》1998,(1):667-675
Several reports exist in the literature citing the decrease in conversion rates of organic-phase catalytic synthesis reactions
when acetic acid is present as a reaction component. This inhibition is thought to result from damage to either the hydration
layer-protein interaction or the overall enzyme structure. In this work, the inhibitory effect of acetic acid on lipase enzyme
activity was ameliorated by conducting syntheses under acetic acid-limiting conditions in a fed-batch system, resulting in
higher product yields. Periodic additions of acetic acid at levels of 40 mM or less gave maximum yields of 65% conversion for the reaction of citronellol and acetic acid to form citronellyl acetate.
The enzyme used was a fungal lipase fromMucor miehei, and was immobilized on macroporous synthetic resin (a Novo lipozyme Novo Nordisk, Denmark). These results represent a fourfold
improvement over batch runs reported in the literature for direct esterification of terpene alcohol with acetic acid using
lipozyme as a catalytic agent. 相似文献
13.
Synthesis of Cyclodextrin Glucosyl Transferase byBacillus cereus for the production of cyclodextrins
R. Jamuna N. Saswathi R. Sheela S. V. Ramakrishna 《Applied biochemistry and biotechnology》1993,43(3):163-176
A potent indigenous bacillus isolate identified asBacillus cereus (RJ-30) was found to produce Cyclodextrin Glucosyl Transferase (CGTase) extracellularly. Process optimization of various
fermentation parameters has been established for optimal growth of bacillus and the maximum enzyme synthesis. The organism
had the highest specific growth rate (0.7μ) with a generation time of 1 h in glucose containing medium at the conditions of
pH 7.0, 37°C at 300 rpm, 1.5 vvm of agitation, and aeration. At these conditions, it exhibited the maximum activity of 54
U/mL at the synthesis rate of 2.7 U/L/h. CGTase was produced from the early exponential growth and peaked during the midsporulating
stage of about 16 h thereafter maintained at the same level of 50 U/mL. Saccharides containing media were better inducers
than starch, and the influence of carbohydrate substrates has shown that enzyme synthesis is promoted by xylose (65 U/mL)
and, more remarkably, by the supplementation of wheat bran extract in glucose medium (106 U/mL). This organism produced CGTase
stably in a chemostat culturing over a period of 400 h with a maximum productivity of 5.4 kU/L/h (threefold higher than obtained
in batch culturing [1.75 kU/L/h]). Comparatively, CGTase was produced by immobilized cells in a continuous fluidized bed reactor
for over approx 360 h, at a relatively high dilution rate of 0.88 h−1 resulting in the productivity of 23.0 kU/L/h. 相似文献
14.
Studies have been carried out using immobilized Z.mobilis in fluidized-bed bioreactors and have emphasized operation during high productivity and conversion. The bacteria are immobilized
within small uniform beads (~1 to 1.5-mm diam) of K-carrageenan at cell loadings of 15-50 g (dry wt)/L. Conversion and productivity
were measured under a variety of conditions, including feedstocks, flow rates, temperature, pH, and column sizes (up to 2.5
m tall). Volumetric productivities of 50-120 g EtOH/h-L reactor volume have been achieved. Productivities of 60 g/h-L are
demonstrated from a 15% feed with residual glucose concentrations of less than 0.1% and 7.4% EtOH in the tallest fermentor.
Among feeds of 10, 15, and 20% dextrose, the 15% gave the highest productivity and avoided substrate inhibition. A temperature
of 30°C and pH 5 were the optimum conditions. The ethanol yield was shown to be nearly constant at 0.49 g EtOH/g glucose,
or 97% of the theoretical under a variety of conditions and transients. The biocatalyst beads have been shown to remain active
for two months. Nonsterile feed has been used for weeks without detrimental contamination. The advantages of this advanced
bioreactor system over conventional batch technology are discussed. 相似文献
15.
Reardon Kenneth F. scheper Thomas Anders Klaus-Dieter Müller Wolfgang Bückmann A. Fritz 《Applied biochemistry and biotechnology》1990,(1):363-374
Typically, NAD(P)H-sensitive culture probes have been used to estimate biomass concentrations in suspended-cell cultivations,
but these sensors have other uses as well. A number of applications, ranging from biosensors to immobilized-cell metabolic
studies, are presented. 相似文献
16.
R. D. Waldron J. L. Vega E. C. Clausen J. L. Gaddy 《Applied biochemistry and biotechnology》1988,18(1):127-142
The bacteriumZymomonas mobilis may be utilized to produce ethanol from glucose in a cross-linked immobilized cell reactor. Reactor startup is much more
rapid with cross-linkedZymomonas than with the yeastSaccharomyces cerevisiae. Volumetric ethanol productivities (based on liquid holdup) three times those obtained with cross-linked yeast, and comparable
to those obtained withZymomonas immobilized by other methods, are possible. 相似文献
17.
Zanin Gisella M. Neitzel Ivo De Moraes Flavio F. 《Applied biochemistry and biotechnology》1993,(1):477-489
The axial dispersion of a liquid fluidized bed of controlled pore silica (CPS) particles has been determined by the pulse
tracer method. The CPS used was the same as for enzyme immobilization, having an average diameter of 0.436 mm and mean pore
size of 37.5 nm. The fluidization liquid is α-amylase liquefied manioc starch, 30% w/v, 45°C pH=4.5. Nominal bed porosities
tested were 0.7 and 0.8. The results show that the axial dispersion coefficient increases with greater superficial liquid
velocities. Various available correlations tested disagree with each other to a large extent and are unable to represent collected
experimental data. 相似文献
18.
Lee Tsu-Shun Weigand William A. Bentley William E. 《Applied biochemistry and biotechnology》1997,(1):743-757
The complete microbial degradation of thiodiglycol (TDG), the primary hydrolysis product of sulfur mustard, byAlcaligenes xylosoxydans ssp.xylosoxydans (SH91) was accomplished in laboratory-scale stirredtank reactors. An Andrews substrate inhibition model was used to describe
the cell growth. The yield factor was not constant, but a relationship with initial substrate concentration has been developed.
Using a substrate-inhibition and variable-yield kinetic model, we can describe the cell growth and substrate consumption in
batch and repeated batch fermentations. Several reactor-operating modes successfully degrade TDG concentration to below 0.5
g/L. According to the experimental results, the two-stage repeated batch operation has the best degradation efficiency, and
it also can degrade 500 mM TDG (≈60 g/L) to 5 mM (≈0.7 g/L) in <5 d. A hypothesis for explaining variable-yield and byproduct
formation based on the capacity and utilization of metabolic loads is presented. 相似文献
19.
Chapatwala Kirit D. Babu G. R. V. Armstead Eddie R. White Evelyn M. Wolfram James H. 《Applied biochemistry and biotechnology》1995,(1):717-726
Pseudomonas putida capable of utilizing organic nitrile (acetonitrile) and inorganic cyanide (sodium cyanide) as the sole source of carbon and
nitrogen was isolated from contaminated industrial sites and waste water. The bacterium possesses nitrile aminohydrolase (EC
3.5.5.1) and amidase (EC 3.5.1.4), which are involved in the transformation of cyanides and nitriles into ammonia and CO2 through the formation of amide as an intermediate. Both of the enzymes have a high selectivity and affinity toward the−Cn group. The rate of degradation of aceotnitrile and sodium cyanide to ammonia and CO2 by the calcium-alginate immobilized cells ofP. putida was studied. The rate of reaction during the biodegradation of acetonitrile and sodium cyanide, and the substrate- and product-dependent
kinetics of these toxic compounds were studied using free and immobilized cells ofP. putida and modeled using a simple Michaelis-Menten equation. 相似文献
20.
Miura Y. Yamada W. Hirata K. Miyamoto K. Kiyohara M. 《Applied biochemistry and biotechnology》1993,(1):753-761
When cells ofChlamydomonas sp. MGA 161, a marine green alga, were cultivated at a high CO2 concentration (15% CO2) and low temperature (15°C), the growth lag time was much longer, but the starch accumulated was two times higher than under
the basal conditions (5% CO2 30°C). When the cells grown in the high-CO2/low-temperature conditions were incubated under dark anaerobic conditions, the degradation of starch and production of hydrogen
and ethanol were remarkably higher than those grown under the basal conditions. The lag time of cell growth was shortened,
whereas the high capacity of starch accumulation and hydrogen production was maintained, by cultivating the cells alternately
every 12 h under the basal and high-CO2/low-temperature conditions. Using this dual system, in which the cultivation was alternated between the two conditions, the
total productivity was significantly improved. 相似文献