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1.
In this study, the immobilization characteristics of Enterococcus faecalis RKY1 for succinate production were examined. At first, three natural polymers—agar, κ-carrageenan, and sodium alginate—were
tried as immobilizing matrices. Among these, sodium alginate was selected as the best gel for immobilization of E. faecalis RKY1. Efficient conditions for immobilization were established to be with a 2% (w/v) sodium alginate solution and 2-mm-diameter
bead. The bioconversion characteristics of the immobilized cellsat various pH values and temperatures were examined and compared
with those of free cells. The optimum pH and temperature of the immobilized cells were the same as for free cells, 7.0 and
38°C respectively, but the conversion ratio was higher by immobilization for all the other pH and temperature conditions tested.
When the seed volume of the immobilized cells was adjusted to 10% (v/v), 30 g/L of fumarate was completely converted tosuccinate
(0.973 g/g conversion ratio) after 12 h. In addition, the immobilized cells maintained a conversion ratio of >0.95 g/g during
4wk of storageat 4°C in a 2% (w/v) CaCl2 solution. In repetitive bioconversion experiments, the activity of the immobilized cells decreased linearly according to
the number of times of reuse. 相似文献
2.
Elisa M. P. Ciapina Walber C. Melo Lidia M. M. Santa Anna Alexandre S. Santos Denise M. G. Freire Nei Pereira Jr. 《Applied biochemistry and biotechnology》1996,131(1-3):880-886
The production of biosurfactant by Rhodococcus erythropolis during the growth on glycerol was investigated. The process was carried out at 28°C in a 1.5-L bioreactor using glycerol
as carbon source. The bioprocess was monitored through measurements of biosurfactant concentration and glycerol consumption.
After 51 h of cultivation, 1.7 g/L of biosurfactant, surface, and interfacial tensions values (with n-hexadecane) of 43 and 15 mN/m, respectively, 67% of Emulsifying Index (E
24), and 94% of oil removal were obtained. The use of glycerol rather than what happens with hydrophobic carbon source allowed
the release of the biosurfactant, originally associated to the cell wall. 相似文献
3.
Jin-Nam Kim Jong-Sok Choo Young-Jung Wee Jong-Sun Yun Hwa-Won Ryu 《Applied biochemistry and biotechnology》2005,123(1-3):861-869
A new acetic acid-producing microorganism, Acetobacter sp. RKY4, was isolated from Korean traditional persimmon vinegar, and we optimized the culture medium for acetic acid production
from ethanol using the newly isolated Acetobacter sp. RKY4. The optimized culture medium for acetic acid production using this microorganism was found to be 40 g/L ethanol,
10 g/L glycerol, 10 g/L corn steep liquor, 0.5 g/L MgSO4·7H2O, and 1.0 g/L (NH4H2PO4. Acetobacter sp. RKY4 produced 47.1 g/L of acetic acid after 48 h of fermentation in a 250 mL Erlenmeyer flask containing 50 mL of the
optimized medium. 相似文献
4.
Chemical characterization of bamboo borer dust (BBD) indicated that it contained 2.5 ±0.5% of an organic entity that was a
watersoluble, acid-labile phosphate, nonreducing sugar with a retention period of 5.2 min on a sugar pack column during high
pressure liquid chromatography (HPLC). It was subsequently identified and confirmed as glucose-1-phosphate (G-l-P) from its
response to phosphoglucomutase and glucose-6-phosphatase treatment. Although the presence of G-l-P in such a large quantity
in BBD is inexplicable, it provides a rare and rich source of G-l-P, making it a potential starting material for its isolation
in pure state. 相似文献
5.
Sarubbo LA Marçal MC Neves ML Silva MP Porto AL Campos-Takaki GM 《Applied biochemistry and biotechnology》2001,95(1):59-67
The yeast Candida lipolytica IA 1055 produced an inducible extracellular emulsification activity while utilizing glucose at different concentrations as
carbon source during batch fermentation at 27°C. In all glucose concentrations studied, maximum production of emulsification
activity was detected in the stationary phase of growth, after pH reached minimal values. The bioemulsifier isolated was a
complex biopolymer constituting proteins, carbohydrates, and lipids. The results obtained in this work show that the biosynthesis
of a bioemulsifier is not simply a prerequisite for the degradation of extracellular hydrocarbon. 相似文献
6.
Song-Dong Ding Guang-Can Zheng Jian-Bing Zeng Li Zhang Yi-Dong Li Yu-Zhong Wang 《European Polymer Journal》2009,45(11):3043-3057
A series of poly[p-dioxanone-(butylene succinate)] (PPDOBS) copolymers were prepared from p-dioxanone (PDO), 1,4-butanediol and succinate acids through a two-step process including the initial prepolymer preparation of poly(p-dioxanone)diol (PPDO-OH) and poly(butylene succinate)diol (PBS-OH) and the following copolymerization of the two kinds of prepolymers by coupling with hexamethylene diisocyanate (HDI). The molecular structures of the prepared PPDO-OH, PBS-OH and PPDOBS were characterized by hydrogen nuclear magnetic resonance spectroscopy (1H NMR). The crystallization of the copolymers was investigated by using differential scanning calorimetry (DSC), polarized optical microscopy (POM) and wide angle X-ray diffraction (WAXD). It has been shown that the crystallization rate and the degree of crystallization increases with the increase of the weight fraction of poly(butylene succinate) (PBS) blocks in the copolymers. In phosphate buffer solution with pH 7.4 at 37 °C for 18 weeks, the hydrolytic degradation behaviors of the copolymers were studied. The changes of retention weight, water absorption, pH value, and surface morphologies with the degradation time showed that the hydrolytic degradation rate of PPDOBS could be controlled by adjusting the weight fraction of poly(p-dioxanone) (PPDO) and PBS blocks in the copolymers. The changes of the thermal properties of PPDOBS during the degradation were also investigated by DSC. 相似文献
7.
One of the next challenges in the use of biocatalysts (enzyme or microbial cells) is the upgrading of biological reactions
of oxidoreduction. The oxidoreductases need cofactors that must be regenerated. Practical experience shows that this is most
readily achieved by using living cells of microorganisms.
Living cells ofSaccharomyces cerevisiae are able to bioconvert vanillin to vanillyl alcohol (1). By working with a two-phase reactor (dodecanol—feeding medium) it
has been possible to use higher vanillin concentrations without inhibiting the bioconversion (2). 相似文献
8.
Four simple and sensitive spectrophotometric methods (A–D) for the determination of Ketotifen fumarate in bulk samples and pharmaceutical formulations are described. They are based on the formation of coloured species by the coupling of the diazotised sulphanilamide with the drug (method A, max 520 nm) or by oxidizing it with excessN-bromo-succinimide and determining the consumed NBS with decrease in colour intensity of celestine blue (method B: max 540 nm) or by the reduction of Folin-Ciocalteau reagent (method C: max 720 nm) or by the formation of a chloroform-soluble, coloured ionassociation complex between the drug and Azocarmine G at pH 1.5 (method D: max 540 nm). Regression analysis of Beer-Lambert plots showed good correlations in the concentration ranges 1–10, 2–12, 4–28 and 2.5–25 g/ml for methods A–D, respectively. The validity of the proposed methods was tested by analysing pharmaceutical formulations containing KTF: the relative standard deviations were within ±1.0%. Recoveries were 98.9–100.2%. 相似文献
9.
Wee Young-Jung Yun Jong-Sun Kang Kui-Hyun Ryu Hwa-Won 《Applied biochemistry and biotechnology》2002,98(1-9):1093-1104
Enterococcus faecalis RKY1, a fumarate-reducing bacterium, was immobilized in an asymmetric hollow-fiber bioreactor (HFBR) for the continuous production
of succinic acid. The cells were inoculated into the shell side of the HFBR, which was operated in transverse mode. Since
the pH values in the HFBR declined during continuous operation to about 5.7, it was necessary to change the feed pH from 7.0
to 8.0 after 24 h of operation in order to enhance production of succinic acid. During continuous operation with a medium
containing fumarate and glycerol, the productivity of succinate was 3.0–10.9 g/(L·h) with an initial concentration of 30 g/L
of fumarate, 4.9–14.9 g/(L·h) with 50 g/L of fumarate, and 7.2–17.1 g/(L·h) with 80 g/L of fumarate for dilution rates between
0.1 and 0.4 h−1. The maximum productivity of succinate obtained by the HFBR (17.1 g of succinate /[L·h]) was 1.7 times higher than that of
the batch bioconversions (9.9 g of succinate /[L·h]) with 80 g/L of fumarate. Furthermore, the long-term stability of the
HFBR was demonstrated with a continuously efficient production of succinate for more than 15 d (360 h). 相似文献
10.
Sheng-Yao Chen Bo Gao Ling-Hao Su Chang-Huan Mi Xiao-Gang Zhang 《Journal of Solid State Electrochemistry》2009,13(9):1361-1366
LiFePO4/C composites were synthesized by pyrolysis of LiFePO4/polypyrrole (PPy), which was obtained by an in situ chemical polymerization involving pyrrole monomer and hydrothermal synthesis LiFePO4. All samples were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy,
cyclic voltammetry, and galvanostatic charge–discharge techniques. The results showed the LiFePO4/C sintered at 800 °C containing 2.8 wt.% carbon exhibited a higher discharge capacity of 49.6 mAh·g−1 at 0.1 C, and bare LiFePO4 only delivered 11.6 mAh·g−1 in 2 M LiNO3 aqueous electrolyte. The possible reason for the improvement of electrochemical performance was discussed and could be attributed
to the formation of aromatic compounds during the carbonization of PPy. 相似文献
11.
Katrlík J Vostiar I Sefcovicová J Tkác J Mastihuba V Valach M Stefuca V Gemeiner P 《Analytical and bioanalytical chemistry》2007,388(1):287-295
Novel and selective microbial amperometric biosensors that use Gluconobacter oxydans cells to monitor the bacterial bioconversion of glycerol (Gly) to 1,3-propanediol (1,3-PD) are described. Two different mediators,
ferricyanide and flexible polyvinylimidazole osmium functionalized polymer (Os-polymer), were employed to prepare two different
microbial biosensors, both of which gave high detection performance. The good operational stabilities of both types of biosensor
were underlined by the ability to detect 1,3-PD throughout 140 h of continuous operation. Both microbial biosensor systems
showed excellent selectivity for 1,3-PD in the presence of a high excess of glycerol [selectivity ratios (1,3-PD/Gly) of 118
or 245 for the ferricyanide and Os-polymer systems, respectively]. Further, the robustness of each microbial biosensor was
highlighted by the high reliability of 1,3-PD detection achieved (average RSD of standards <2%, and well below 4% for samples).
The biosensor implementing the Os-polymer mediator exhibited high selectivity towards 1,3-PD detection and allowed moderate
sample throughput (up to 12 h−1) when integrated into a flow system. This system was used to monitor the concentration of 1,3-PD during a real bioprocess.
Results from biosensor assays of 1,3-PD in bioprocess samples taken throughout the fermentation were in a very good agreement
with results obtained from reference HPLC assays (R
2 = 0.999). 相似文献
12.
J. Pablo Lamas Lucia Sanchez-Prado Jorge Regueiro Maria Llompart Carmen Garcia-Jares 《Analytical and bioanalytical chemistry》2009,394(8):2231-2239
A method for the determination of dimethyl fumarate (DMF), benzothiazole (BT) and tert-butylphenol (TBP) in desiccant and antimould agents employed for protecting consumer products from humidity and mould has
been developed. The method is based on ultrasound-assisted extraction (UAE) followed by GC-MS analysis. Parameters that could
affect the extraction of the compounds have been optimised using a multivariate approach. In the final conditions, the extraction
is performed using only 0.5 or 1 mL ethyl acetate and applying ultrasound energy for 5 min. Simultaneous extractions could
also be carried out in 5 min without losing efficiency. The method was validated showing good linearity (R
2 >0.995). Both intra- and inter-day precisions were studied at several concentration levels, being satisfactory in all cases
(RSD <10%). Recovery was evaluated in four real desiccant samples at different compound concentrations, ranging between 87%
and 109%. Limits of detection and quantification were in the low nanogramme per gramme level, thus allowing the determination
of DMF at concentrations well below the limit established by the recent EU Directive (0.1 μg/g). The proposed procedure was
applied to the determination of the target compounds in several desiccant and antimould samples. Although most of them were
simply labelled as “silica gel”, more than 70% of the tested samples contained high amounts of DMF, many of them at the high
microgram per gramme level. Many samples also showed the presence of the other two potential allergens. These results demonstrate
that the content of the “desiccant” sachets and tablets in consumer products does not usually belong with the label of the
desiccant, and hence, the high risk of exposition to the powerful allergen DMF and other potentially harmful chemicals through
consumer goods should be a matter of concern. 相似文献
13.
Five cassava flour wastewater (manipueira) preparations were tested as culture media for biosurfactant production by a wild-type Bacillus sp. isolate. No-solids (F), no-solids diluted (F/2), natural (I), natural diluted (I/2), and decanted (IPS) were the tested
manipueira media. The microorganism was able to grow and to produce biosurfactant on all manipueira preparations. The media whose solids were removed (F and F/2) showed better results than preparations with the presence of
solids (I, I/2, and IPS). No-solids medium (F) showed a surface tension of 26,59 mN/m and reciprocal of critical micelle concentration
of over 100 and was selected as a potential substrate for biosurfactant production. 相似文献
14.
Glycerol production from xylose fermentation usingRhizopus javanicus (ATCC 22581) has been investigated in shake flasks. The medium composition (xylose concentration, nitrogen sources), aeration
rate, and temperature have been found to affect the accumulation and yield of glycerol. Some of these effects are explained
in terms of the critical parameters, osmotic pressure, and dissolved oxygen levels in the medium. Relatively high glycerol
yields and concentrations have been obtained at high sugar concentration with high level of aeration at room temperature.
The addition of polyethylene glycol or sulfite can improve the yield and accumulation of glycerol. 相似文献
15.
Physicochemical and biologic analysis of dairy wastewater showed that the effluent had a high organic load (chemical oxygen
demand [COD]: 5095 mg/L), an acidic pH (6.4), and a high probability of coliforms (most probable number [MPN]>1100). The various
bacterial strains isolated and purified were identified as Sporolactobacillus sp., Citrobacter sp., Pseudomonas sp., Alcaligenes sp., Bacillus sp., Staphylococcus sp., and Proteus sp., as per the Bergey’s manual of systematic bacteriology. Among the five selected bacterial strains, the strain designated
as MMRR7 and identified as Alcaligenes sp. was found to give a maximum reduction in COD (62%) in 5 d of incubation. Chemical coagulation using alum at a concentration
of 0.5 g/100 mL was found to be effective in the primary treatment of the effluent. Studies on free-cell treatment of the
coagulated effluent with the selected bacterial strain Alcaligenes sp. MMRR7 gave a maximum COD reduction of 91% in 120 h. This study clearly indicates the possibility of using Alcaligenes sp. MMRR7 for the effective treatment of dairy wastewater. 相似文献
16.
17.
The gpdA-promoter-controlled exocellular production of glucose oxidase (GOD) by recombinant Aspergillus niger NRRL-3 (GOD3-18) during growth on glucose and nonglucose carbon sources was investigated. Screening of various carbon substrates
in shake-flask cultures revealed that exocellular GOD activities were not only obtained on glucose but also during growth
on mannose, fructose, and xylose. The performance of A. niger NRRL-3 (GOD3-18) using glucose, fructose, or xylose as carbon substrate was compared in more detail in bioreactor cultures.
These studies revealed that gpdA-promoter-controlled GOD synthesis was strictly coupled to cell growth. The gpdA-promoter was most active during growth on glucose. However, the unfavorable rapid GOD-catalyzed transformation of glucose
into gluconic acid, a carbon source not supporting further cell growth and GOD production, resulted in low biomass yields
and, therefore, reduced the advantageous properties of glucose. The total (endo- and exocellular) specific GOD activities
were lowest when growth occurred on fructose (only a third of the activity that was obtained on glucose), whereas utilization
of xylose resulted in total specific GOD activities nearly as high as reached during growth on glucose. Also, the portion
of GOD excreted into the culture fluid reached similar high levels (≅ 90%) by using either glucose or xylose as substrate,
whereas growth on fructose resulted in a more pelleted morphology with more than half the total GOD activity retained in the
fungal biomass. Finally, growth on xylose resulted in the highest biomass yield and, consequently, the highest total volumetric
GOD activity. These results show that xylose is the most favorable carbon substrate for gpdA-promoter-controlled production of exocellular GOD. 相似文献
18.
Min Hyung Kang Haiying Ni Thomas W. Jeffries 《Applied biochemistry and biotechnology》2003,106(1-3):265-276
Candida boidinii produces significant amounts of xylitol from xylose, and assays of crude homogenates for aldose (xylose) reductase (XYL1p)
have been reported to show relatively high activity with NADH as a cofactor even though XYL1p purified from this yeast does
not have such activity. A gene coding for XYL1p from C. boidinii (CbXYL1) was isolated by amplifying the central region using primers to conserved domains and by genome walking. CbXYL1 has an open reading frame of 966 bp encoding 321 amino acids. The C. boidinii XYL1p is highly similar to other known yeast aldose reductases and is most closely related to the NAD(P)H-linked XYL1p of
Kluyveromyces lactis. Cell homogenates from C. boidinii and recombinant Saccharomyces cerevisiae were tested for XYL1p activity to confirm the previously reported high ratio of NADH:NADPH linked activity. C. boidinii grown under fully aerobic conditions showed an NADH:NADPH activity ratio of 0.76, which was similar to that observed with
the XYL1p from Pichia stipitis XYL1, but which is much lower than what was previously reported. Cells grown under low aeration showed an NADH:NADPH activity
ratio of 2.13. Recombinant S. cerevisiae expressing CbXYL1 showed only NADH-linked activity in cell homogenates. Southern hybridization did not reveal additional bands. These results
imply that a second, unrelated gene for XYL1p is present in C. boidinii. 相似文献
19.
Force measurements of bacterial adhesion on metals using a cell probe atomic force microscope 总被引:1,自引:0,他引:1
The adhesion of microbial cells to metal surfaces in aqueous media is an important phenomenon in both the natural environment and engineering systems. The adhesion of two anaerobic sulfate-reducing bacteria (Desulfovibrio desulfuricans and a local marine isolate) and an aerobe (Pseudomonas sp.) to four polished metal surfaces (i.e., stainless steel 316, mild steel, aluminum, and copper) was examined using a force spectroscopy technique with an atomic force microscope (AFM). Using a modified bacterial tip, the attraction and repulsion forces (in the nano-Newton range) between the bacterial cell and the metal surface in aqueous media were quantified. Results show that the bacterial adhesion force to aluminum is the highest among the metals investigated, whereas the one to copper is the lowest. The bacterial adhesion forces to metals are influenced by both the electrostatic force and metal surface hydrophobicity. It is also found that the physiological properties of the bacterium, namely the bacterial surface charges and hydrophobicity, also have influence on the bacteria-metal interaction. The adhesion to the metals by Pseudomonas sp. and D. desulfuricans was greater than by the marine SRB isolate. The cell-cell interactions show that there are strong electrostatic repulsion forces between bacterial cells. Cell probe atomic force microscopy has provided some useful insight into the interactions of bacterial cells with the metal surfaces. 相似文献
20.
Succinic acid was produced efficiently from fumaric acid by a recombinantE. coli strain DH5αt/pGC1002 containing multicopy fumarate reductase genes. The effects of initial fumaric acid and glucose concentration
on the production of succinic acid were investigated. Succinic acid reached 41 to over 60 g/L in 48.5 h starting with 50 to
64 g/L fumaric acid. Significant substrate inhibition was observed at initial fumaric acid concentration of 90 g/L. L-Malic
acid became the major fermentation product under these conditions. Provision of glucose (5-30 g/L) to the fermentation medium
stimulated the initial succinic acid production rate over two folds. 相似文献