共查询到20条相似文献,搜索用时 62 毫秒
1.
Kaster Jeffrey A. Michelsen Donald L. Velander William H. 《Applied biochemistry and biotechnology》1990,(1):469-484
A microbubble dispersion (MBD) was used to supply oxygen for aerobic fermentations in a standard 2 L stirred tank fermenter.
The microbubble dispersion was formed using only surfactants produced naturally. Growth rates ofSaccharomyces cerevisiae cultures were found to be equal or greater with MBD sparging than with gas sparging. The oxygen transfer coefficent with
MBD sparging was found to be 190/h and independent of impeller speed from 100–580 rpm. The oxygen transfer coefficient with
air sparging rose from 55 to 132/h over the same range of impeller speeds. Power requirements for the fermenter systems were
estimated. 相似文献
2.
Grethlein A. J. Worden R. M. Jain M. K. Datta R. 《Applied biochemistry and biotechnology》1990,(1):875-884
Continuous, steady-state fermentations using carbon monoxide gas as the sole carbon and energy source have been achieved with
the CO strain ofButyribacterium methylotrophicum. Fermentation pH was found to regulate carbon monoxide metabolism over the pH range of 6.8 to 5.0. Cell growth diminished
at low pH, with washout occurring at pH 5.0. As observed previously in batch culture, lower pH values favored production of
butyrate over acetate. The mechanism responsible for this trend is currently being investigated by quantification of key intracellular
enzyme activities.
At low pH values, direct, steady-state fermentation of carbon monoxide to alcohols has been verified. Of major significance
is the production of butanol from carbon monoxide in pure culture. This newly identified pathway provides a potential mechanism
for direct bioconversion of synthesis gas to butanol. 相似文献
3.
G. K. Ziyatdinova E. R. Giniyatova H. C. Budnikov 《Journal of Analytical Chemistry》2012,67(5):467-473
As established, α-tocopherol is electrochemically active on glassy carbon electrode in the available range of anodic potentials
in acetonitrile and its aqueous mixtures. However, an increase in the water percentage up to 50% and beyond leads to a substantial
decrease and then the total disappearance of the analytical signal. A scheme of electrode reaction responsible for the signal
formation is proposed. The effect of surfactants on the oxidation of α-tocopherol in aqueous acetonitrile is estimated. As
found, surfactants (N-dodecylpyridinium bromide, Triton X-100 and N-cetylpyridinium bromide) enhance the current of α-tocopherol oxidation. The surfactants reduce the detection limit and extend
the analytical range. Analytical methods for the voltammetric quantification of α-tocopherol in drugs in the presence of surfactants
are elaborated and may be recommended for the control of pharmaceuticals. 相似文献
4.
Polystyrene latexes with a narrow size distribution (Dw/Dn < 1.05) were prepared with a large range of particle sizes (from 40 to 800 nm) in the presence of various amphoteric sulfobetaine surfactants. The influence of the nature of the surfactant and of the ionic strength, the pH and solid content were studied. The results are discussed and compared with those obtained using sodium dodecyl sulfate or in the absence of surfactants. 相似文献
5.
The volumetric productivity of many fermentations is productlimited.In situ removal of these products with liquid organic extractants is limited by either a low product distribution coefficient or
toxicity of the extractant. This paper presents results from studies using mixed extractants, namely mixtures of toxic extractants
that have high distribution coefficients for the product and nontoxic extractants that have low distribution coefficients.
The production of butanol byClostridium acetobutylicum was chosen as a model system for these studies. The mechanisms of toxicity of mixed extractants and the observed responses
to their presence are discussed. 相似文献
6.
Inhibition of microbial xylitol production by acetic acid and its relation with fermentative parameters 总被引:5,自引:0,他引:5
Precipitated sugarcane bagasse hemicellulosic hydrolysate containing acetic acid was fermented by Candida guilliermondii FTI 20037 under different operational conditions (pH 4.0 and 7.0, three aeration rates). At pH 7.0 and k
L
a of 10 (0.75 vvm) and 22.5/h (3.0 vvm) the acetic acid had not been consumed until the end of the fermentations, whereas at
the same pH and k
L
a of 35/h (4.5 vvm) the acid was rapidly consumed and acetic acid inhibition was not important. On the other hand, fermentations
at an initial pH of 4.0 and k
L
a of 22.5 and 35/h required less time for the acid uptake than fermentations at k
L
a of 10/h. The acetic acid assimilation by the yeast indicates the ability of this strain to ferment in partially detoxified
medium, making possible the utilization of the sugarcane bagasse hydrolysate in this bioprocess. The effects on xylitol yield
and production are reported. 相似文献
7.
Shengbo Wang Changlong Chen Mohannad J. Kadum Jeffrey H. Harwell 《Journal of Dispersion Science and Technology》2018,39(5):734-743
Several new foaming agent formulations (surfactants and polymers) in the presence of multi-walled carbon nanotube (MWCNT) were developed in 3% salinity (NaCl, 2.4?wt%, CaCl2, 0.6?wt%). The dispersion stability of the MWCNT and the viscosity of the solutions were examined as a prerequisite for reservoir applications. Foam was generated in situ and one-dimensional flow-through tests were performed by co-injecting air and foaming solution either in the presence of MWCNT or at particle-free condition. The pressure drop (Δp) across the sand-pack and the nanoparticles breakthrough were closely monitored. The fluid injection rate, gas fraction, and the effect of MWCNT on foams in porous media were investigated.Our results reveal that foams stabilized by the selected nanoparticles are capable of generating stronger foams leading to higher apparent Δp. The Δp profile varies with gas fraction, which largely affects the foam texture and quality. Also, the viscosity of foaming agent solutions influences Δp values. Adding MWCNT to the foaming agent solutions appears beneficial to the flooding as surfactants adsorption onto nanoparticle surfaces, which facilitates surfactants partitioning to the G/L interface.Addition of nanoparticles in the developed foam formulations leads to the formation of high-quality stronger foams in porous media, which could potentially improve the sweep efficiency and increase the oil recovery. 相似文献
8.
Xiu‐Kui Qu Feng Liu Xi‐Lian Wei Zhong‐Ni Wang Gan‐Zuo Li 《Journal of Dispersion Science and Technology》2013,34(5):779-784
The association of α‐, β‐ and γ‐cyclodextrin (α‐CD, β‐CD and γ‐CD) with sodium dodecyl polyoxyethylenated sulfonate (C12EnS n=1, 3) was studied by means of isothermal titration calorimetry and 1H NMR measurements in aqueous solution at T=298.15 K. The results indicate that the binding processes of β‐CD with the surfactants are characterized by both enthalpy favorable and entropy favorable, while those of α‐CD or γ‐CD with the surfactants are mainly entropy driven. The stoichiometry of β‐CD binding with the surfactants is different with different numbers of oxyethyl groups in surfactant molecules, while that of α‐CD or γ‐CD binding with the surfactants makes no difference. The 1H NMR spectra reveal that chemical shift data of all protons in α‐CD, β‐CD and γ‐CD molecules move to high field in the presence of C12EnS, which can be regarded as a microscopic evidence of the occurrence of inclusion interaction. 相似文献
9.
L. M. Landoll 《Journal of polymer science. Part A, Polymer chemistry》1982,20(2):443-455
Nonionic water-soluble polymeric surfactants have been prepared by addition of long-chain n-alkyl epoxides to nonionic cellulose ethers. The polymers exhibit properties which can be explained by interchain association. The relationship between hydrocarbon-modifier carbon number and the onset of association follows a linear relation analogous to those observed for monomeric nonionic surfactants. 相似文献
10.
Preparation of substituted ionic carbohydrate polymers and their interactions with ionic surfactants
The formation of micelles of hexadecyltrimethylammonium chloride (CTAC) and sodium dodecylsulfate (SDS) in aqueous solutions containing charged polysaccharides was studied by steady-state and time-resolved fluorescence measurements using pyrene as a photophysical probe. Micropolarity studies using the
I1/I3 ratio of the vibronic emission bands of pyrene and the behaviour of the
IE/IM ratio between the excimer and monomer emissions show the formation of hydrophobic domains. The interactions between the polyelectrolytes and surfactants of opposite charge lead to the formation of induced pre-micelles at surfactant concentrations lower than the critical micellar concentration (cmc) of the surfactants. At similar concentrations, the
IE/IM ratio shows a peak. This aggregation process is assumed to be due to electrostatic attractions. At higher surfactant concentrations, near the critical micellar concentration, micelles with the same properties as those found in pure aqueous solution are formed. On the other hand, systems containing polyelectrolytes and surfactants of the same charge do not show this behaviour at low concentrations. The presence of long alkyl chains bound to the polyelectrolytes also induces the formation of free micelles at concentrations somewhat below the aqueous cmc. 相似文献
11.
Masahide Yasuda Yoshimasa Nishinaka Takumi Nakazono Takeshi Hamasaki Nobuya Nakamura Tsutomu Shiragami Chyongjin Pac Kensuke Shima 《Photochemistry and photobiology》1998,67(2):192-197
It was found that tetra-o-acyl riboflavins efficiently photosensitize the monomerization of the cis, syn-cyclobutane dimers of 1,3-dimethylthymine and 1,3-dimethyluracil in aqueous solution in the presence of such anionic surfactants as sodium dodecyl sulfate and sodium hexadecyl sulfate at concentrations higher than their critical micelle concentration, while little monomerization of the dimers was photosensitized by the flavins in the absence of the surfactants and even in the presence of cationic and nonionic surfactants. 相似文献
12.
Citric acid is finding new areas of use each year and the demand for the acid is constantly increasing. Being a bulk chemical,
the continuous production of citric acid would be advantageous. The paper presents the results from ammonia limited batch
and continuous fermentations using the yeast strainSaccharomycopsis (Candida) lipolytica (NRRL Y-7576). Mathematical models were developed for growth and glucose utilization in batch and continuous culture. Cell
and acid yields appeared to be almost the same in batch and continuous culture. The specific production rates were found to
be constant, equal to 0.053 g/g h, in the batch fermentations but varied in the continuous experiments from 0 to 0.11 g/g
h depending on the fermentation conditions. Continuous production in a single stage CSTR was studied for over 1,000 hours
without shutdown. 相似文献
13.
Nascimento Hilton J. Soares Valeria F. Bon Elba P. S. Silva José G. 《Applied biochemistry and biotechnology》1998,(1):641-650
The proportion of glucoamylases, GAI and GAII, in the culture supernatant ofAspergillus awamori fermentations depends on the medium C/N ratio in such a way that the transformation of GAI into GAII is favored by the existence
of a surplus of the carbon source in the growth medium. This condition also favors the appearance of the proteolytic activity.
The authors report the observation that the shift in the isoenzyme proportion was concomitant to the peak of proteolytic activity.
A peptide that may have resulted from the continuous degradation of the GAI C-terminal peptide, Gp-1, was isolated by gel
filtration and purified by reversephase chromatography. This peptide matched with the region G14-A34 of the substrate-binding domain of GAI, thus reinforcing the hypothesis of the extracellular proteolytic processing of GAI. 相似文献
14.
The free radical dispersion polymerization of 2-hydroxyethyl methacrylate (HEMA) has been carried out in supercritical carbon dioxide (scCO2) and compressed liquid DME using several surfactants. The polymerization are performed in the presence of fluorine-based poly(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl acrylate) [poly(HDFDA)], poly(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl methacrylate) [poly(HDFDMA)], or poly(HDFDMA-co-MMA) and siloxane-based PDMS-g-pyrrolidonecarboxylic acid (Monasil PCA™) or PDMS modified surfactants, SS-5050K™ and KF6017™ as polymerization surfactants. When scCO2 was used as a polymerization medium, the PHEMA were heavily agglomerated. However, the spherical and relatively uniform poly(2-hydroxyethyl methacrylate) (PHEMA) particles could be produced even at 20 bar, with a narrow particle size distribution in compressed liquid DME. It was observed that fluorine-based surfactants were not a good surfactant as siloxane-based surfactants for the dispersion polymerization of HEMA. The average particle size of PHEMA was shown to be dependent on the type of the surfactant, the amount of the surfactant and initiator added to the system. The effect of two continuous phases, which are scCO2 and compressed liquid DME, as a polymerization medium, the surfactant types and the concentration, initiator concentration, and monomer concentration on the morphology and size of the polymer particles was also investigated. 相似文献
15.
The economics of large-scale production of fuel ethanol from biomass and wastes requires the efficient utilization of all
the sugars derived from the hydrolysis of the heteropolymeric hemicellulose component of lignocellulosic feedstocks. Glucuronic
and 4-0-methyl-glucuronic acids are major side chains in xylans of the grasses and hardwoods that have been targeted as potential
feedstocks for the production of cellulosic ethanol. The amount of these acids is similar to that of arabinose, which is now
being viewed as another potential substrate in the production of biomass-derived ethanol.
This study compared the end-product distribution associated with the fermentation of D-glucose (Glc) and D-glucuronic acid
(GlcUA) (as sole carbon and energy sources) byEscherichia coli B (ATCC 11303) and two different ethanologenic recombinants—a strain in whichpet expression was via a multicopy plasmid (pLOI297) and a chromosomally integrated construct, strain KO11. pH-stat batch fermentations
were conducted using a modified LB medium with 2% (w/v) Glc or GlcUA with the set-point for pH control at either 6.3 or 7.0.
The nontransformed host culture produced only lactic acid from glucose, but fermentation of GlcUA yielded a mixture of ethanol,
acetic, and lactic acids, with acetic acid being the predominant end-product. The ethanol yield associated with GlcUA fermentation
by both recombinants was similar, but acetic acid was a significant by-product. Increasing the pH from 6.3 to 7.0 increased
the rate of glucuronate fermentation, but it also decreased the ethanol mass yield from 0.22 to 0.19 g/g primarily because
of an increase in acetic acid production. In all fermentations there was good closure of the carbon mass balance, the exception
being the recombinant bearing plasmid pLOI297 that produced an unidentified product from GlcUA. The metabolism of GlcUA by
this metabolically engineered construct remains unresolved. The results offered insights into metabolic fluxes and the regulation
of pyruvate catabolism in the wild-type and engineered strains. End-product distribution for metabolism of glucuronic acid
by the nontransformed, wild-typeE. coli B and recombinant strain KO11 suggests that the enzyme pyruvate-formate lyase is not solely responsible for the production
of acetylCoA from pyruvate and that derepressed pyruvate dehydrogenase may play a significant role in the metabolism of GlcUA. 相似文献
16.
V. P. Meshalkin V. A. Kolesnikov A. V. Desyatov A. D. Milyutina A. V. Kolesnikov 《Doklady Chemistry》2017,476(1):219-222
Electroflotation of finely divided carbon nanomaterials—carbon nanoflakes (CNFls)—from aqueous solutions with a wide pH range of 3.0 to 11.0 in the presence of surfactants of various types was studied experimentally. The efficiency indices were determined for the electroflotation of CNFls from CNFls–surfactant–Na2SO4 solutions in the presence of a coagulant (iron(III) chloride) and flocculants, which enabled one to find the optimal conditions for electroflotation of carbon nanomaterials. 相似文献
17.
Conformations of poly(L-lysine) (PLL) and poly(L-ornithine) (PLO) were examined in aqueous solutions of sodium alkanesulfontates (CnSO3Na, n=9, 10, 11, 12) in the presence of 0.02 M NaCl by circular dichroism (CD) spectroscopy. These surfactants induce the-structure for PLL and the-helix for PLO. The binding of surfactants on the polypeptides was measured potentiometrically with a surfactant ion electrode and was found to be highly cooperative. The cooperativity increases with increasing chain length of surfactant. The behavior accompanying the surfactant binding and the conformational change indicated that the conformational change requires a certain amount of bound surfactants in the case of C9SO3Na and starts immediately on binding of surfactant in the case of C1
2SO3Na. The clustering of bound surfactants due to the cooperative binding as well as neutralization of polypeptides contributes to their conformational change. A slow conformational change of PLO was found in the time scale of hours, sometimes days, for C9- and C10SO3Na at low concentrations, but the binding process reached the equilibrium quickly. This slow mode might occur due to the slow interaction between surfactant/polypeptide complexes. 相似文献
18.
Heloiza Ferreira Alves-Prado Eleni Gomes Roberto Da Silva 《Applied biochemistry and biotechnology》2006,129(1-3):234-246
Cyclodextrin glycosyltransferase (CGTase) is an enzyme that produces cyclodextrins from starch by an intramolecular transglycosylation
reaction. Cyclodextrins have been shown to have a number of applications in the food, cosmetic, pharmaceutical, and chemical
industries. In the current study, the production of CGTase by Paenibacillus campinasensis strain H69-3 was examined in submerged and solid-state fermentations. P. campinasensis strain H69-3 was isolated from the soil, which grows at 45°C, and is a Gramvariable bacterium. Different substrate sources
such as wheat bran, soybean bran, soybean extract, cassava solid residue, cassava starch, corn starch, and other combinations
were used in the enzyme production. CGTase activity was highest in submerged fermentations with the greatest production observed
at 48–72 h. The physical and chemical properties of CGTase were determined from the crude enzyme produced from submerged fermentations.
The optimum temperature was found to be 70–75°C, and the activity was stable at 55°C for 1 h. The enzyme displayed two optimum
pH values, 5.5 and 9.0 and was found to be stable between a pH of 4.5 and 11.0. 相似文献
19.
Irfan Ullah Musa Kaleem Baloch Gulrez Fatima Durrani 《Journal of solution chemistry》2012,41(2):215-222
The solubility of an anesthetic drug, LIDOCAINE, in water was investigated in the presence of ionic, nonionic and zwitterionic
surfactants at 25 °C, and the solubility was found to increase linearly with the surfactant concentration. The molar solubilization
ratio, R
m,s, and Gibbs free energy, DGso\Delta G_{\mathrm{s}}^{\mathrm{o}} values for nonionic surfactants fall in the order DDAO > Brij 35 > Brij 30, whereas for ionic and zwitterionic surfactants
the order is DDAPS > DTAB > SDS. The high negative values of the Gibbs energies in the cases of DDAO and DDAPS prove them
to be better surfactants for solubilizing this drug as compared to the other surfactants. 相似文献
20.
The spectroscopic and kinetic studies of the interaction between bacteriorhodopsin in the M-intermediate and several surfactants (cetyl trimethyl ammonium bromide, dodecyl trimethyl ammonium bromide, diethylene glycol mono-n-hexyl ether, ethylene glycol mono-n-hexyl ether, sodium 1-decanesulfonate and sodium 1-heptanesulfonate) have been investigated using steady-state UV–VIS spectrometry and time-resolved absorption techniques. The steady-state spectral results show that bR retains its trimeric state. Time-resolved observations indicate that the rate of deprotonation of the protonated Schiff base increases in the presence of the cationic surfactants, whereas insignificant changes are observed in the neutral or anionic surfactants. The rate of the reprotonation of the Schiff base in the transition M → N is accelerated in anionic and neutral surfactants, but is decelerated in the presence of the cationic surfactants. Surfactants with a longer hydrocarbon tail have a greater effect on the kinetics when compared with surfactants having shorter hydrocarbon tails. The opposite effect is observed when the hydrophilic head of the surfactants contains opposite charges. These distinct kinetics are discussed in terms of the difference in the modified surface hydrophilicity of the bR and the possible protein configurational changes upon surfactant treatments. 相似文献