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1.
During L-lactic acid fermentation by Rhizopus oryzae, increasing the phosphate level in the fermentation medium from 0.1 g l–1 to 0.6 g l–1 KH2PO4 reduced the maximal concentration of L-lactic acid and fumaric acid from 85 g l–1 to 71 g l–1 and from 1.36 g l–1 to 0.18 g l–1, respectively; and it decreased the fermentation time from 72 h to 52 h. Phosphate at 0.40 g l–1 KH2PO4 was suitable for both minimizing fumaric acid accumulation and benefiting L-lactic acid production.  相似文献   

2.
A. H. Hyde 《Plant and Soil》1966,24(2):328-332
Summary The rates of phosphate uptake of young intact plants were measured in solution at concentrations between 3.2×10–7 M and 3.2×10–5 M KH2PO4. The addition of 0.005 to 0.01M CaCl2 increased the uptake rates to values of up to 4 times those of controls. The increases in uptake relative to the controls were most marked at the lowest phosphate concentrations. The addition of KCl also increased the uptake rates, but to a much smaller extent. The results are analyzed by the enzyme kinetic theory, and it is concluded that the uptake of phosphate at low ionic strengths is impeded by negative potentials at the root surface.The experimental results in this letter have appeared in a thesis.  相似文献   

3.
Direct ammonium fumarate production from glucose-based media with Rhizopus arrhizus NRRL 1526 was obtained using 2-kmol (NH4)2CO3 per-m3 as neutralising agent and controlling mycelial growth by phosphorous (P) limitation. As the P level in the production medium was increased from 0 to 0.3-kg of KH2PO4 per m3, the fumarate yield decreased from 0.32 to 0.13-g per-g of glucose consumed; maximum ammonium fumarate productivity (0.46-kg-m–3-h–1) was obtained when using 0.1-kg phosphate-m–3.  相似文献   

4.
Liu C  Liu Y  Liao W  Wen Z  Chen S 《Biotechnology letters》2003,25(11):877-882
Statistically-based experimental designs were applied for the optimization of nisin production by Lactococcus lactis in a whey-based medium. Yeast extract, KH2PO4, and MgSO4 were identified to have significant effects on nisin biosynthesis by a Plackett–Burman design. These three significant factors were subsequently optimized using central composite design, and the optimal conditions were determined to be 12.067 g l–1 for yeast extract, 0.569 g l–1 for KH2PO4, and 0.572 g l–1 for MgSO4. The validity of the optimal conditions was verified by a separate experiment.  相似文献   

5.
The subcellular distribution and kinetic properties of carbonic anhydrase were examined in red blood cells and gills of the lamprey, Petromyzon marinus, a primitive agnathan, and rainbow trout, Oncorhynchus mykiss, a modern teleost, in relation to the evolution of rapid Cl/HCO 3 exchange in the membrane of red blood cells. In the lamprey, which either lacks or has minimal red cell Cl/HCO 3 exchange, there has been no compensatory incorporation of carbonic anhydrase into the membrane fraction of either the red cell or the gill. Carbonic anhydrase activity in red cells is exclusively cytoplasmic, and the single isozyme displays kinetic properties typical of the type I, slow turnover, isozyme. In the red blood cells of the trout, however, which possess high amounts of the band-3 Cl/HCO 3 exchange protein, the single carbonic anhydrase isozyme appears to be kinetically similar to the type II, fast turnover, isozyme. It thus appears that the type I isozyme present in the red blood cells of primitive aquatic vertebrates was replaced in modern teleosts by the kinetically more efficient type II isozyme only after the incorporation and expression of a significant amount of the band-3 exchange protein in the membrane of the red cell.Abbreviations BCIP 5-bromo-4-chloro-3-indolyl phosphate - CA carbonic anhydrase - DTT dithiothreitol - EDTA ethylenediaminetetra-acetate - E 0 total concentration of free enzyme - i fractional inhibition of enzyme activity - IU international units - K 1 inhibition constant - K M Michaelis constant - NBT nitro blue tetrazolium - NCP nitrocellulose paper - RBC red blood cell - SDS-PAGE sodium dodecyl sulphate polyacrylamide gel electrophoresis - V max maximal velocity of reaction  相似文献   

6.
Summary The effect of cholecystokinin (CCK) and internal Ca2+ on outward K+ current in isolated pig pancreatic acinar cells has been investigated using the patch-clamp method for whole-cell current recording under voltage-clamp conditions. CCK (2 × 10–10 M) applied to the bath evoked a marked increase in the outward K+ current associated with depolarizing voltage steps, and this effect was fully reversible and acutely dependent on the presence of external Ca2+. When strongly buffered Ca2+-EGTA solutions were used inside the cells CCK failed to evoke an effect. Increasing the internal Ca2+ concentration ([Ca2+] i ) from 5 × 10–10 M to 10–7 and 5 × 10–7 M mimicked the effect of CCK. It would appear therefore that CCK controls K+ conductance in the acinar cells via changes in the internal free ionized Ca2+ concentration.  相似文献   

7.
A HPLC–UV determination of loratadine in human plasma is presented. After simple liquid–liquid extraction with 2-methylbutane–hexane (2:1) and evaporation of organic phase the compounds were re-dissolved in 0.01 M HCl, evaporated again and finally separated on a Supelcosil LC-18-DB column. The analyses were done at ambient temperature under isocratic conditions using the mobile phase: CH3CN–water–0.5 M KH2PO4–H3PO4 (440:480:80:1, v/v). UV detection was performed at 200 nm with a limit of quantification of 0.5 ng/ml. The precision was found to be satisfactory over the whole range tested (0.5–50 ng/ml) with relative standard deviations of 2.3–6.3 and 5.2–14.1% for intra- and inter-assays, respectively.  相似文献   

8.
The effect of medium components (carbon, nitrogen, and mineral sources) and environmental factors (initial pH and temperature) for mycelial growth and exopolysaccharide (EPS) production in Sarcodon aspratus(Berk) S.lto TG-3 was investigated. The optimal temperature (25°C) and initial pH (5.0) for the EPS production in shake flask cultures of S. aspratus were determined using the two-dimensional contour plot. The most suitable carbon, nitrogen, and mineral sources for EPS production were glucose, yeast extract, CaCl2 and KH2PO4, respectively. Notably, the EPS production was significantly enhanced by supplementation of calcium ion. Subsequently, the optimum concentration of glucose (30gl–1), yeast extract (15gl–1), CaCl2 (1.1gl–1), and KH2PO4 (1.2gl–1) were determined using the orthogonal matrix method. The effects of nutritional requirement on the mycelial growth of S.aspratuswere in regular sequence of glucose>KH2PO4>yeast extract>CaCl2, and those on EPS production were in the order of glucose>yeast extract>CaCl2>KH2PO4. Under the optimal culture conditions, the maximum EPS concentration in a 5-l stirred-tank reactor was 2.68gl–1 after 4days of fermentation, which was 6-fold higher than that at a basal medium. The two-dimensional contour plot and orthogonal matrix method allowed us to find the relationship between environmental factors and nutritional requirement by determining optimal operating conditions for maximum EPS production in S.asparatus. The statistical experiments used in this work can be useful strategies for optimization of submerged culture processes for other mushrooms.  相似文献   

9.
The effects of tissue culture conditions and explant characteristics on direct somatic embryogenesis were studied on Oncidium `Gower Ramsey'. Embryo formation was significantly affected by explant position. Leaf tip segments had a significantly higher embryogenic response than other segments of leaves. Adaxial-side-up orientation significantly promoted embryogenesis in comparison with abaxial-side-up orientation. There was no significant effect of sucrose in a range of concentrations (10–60 g l–1). Modified 1/2-MS medium (containing 85 mg l–1 KH2PO4) supplemented with 170 mg l–1 NaH2PO4 significantly promoted direct somatic embryogenesis. Peptone at 0.5 mg l–1 gave significantly higher emrbyogenic response (80%) on leaf tips than control treatment (50%). The best response on direct embryo formation was obtained on the modified 1/2-MS medium supplemented with 10–20 g l–1 sucrose, 170 mg l–1 NaH2PO4 and 0.5 g l–1 peptone.  相似文献   

10.
The binding of the enkephalin dimer [d-Ala2, Leu5-NH-CH2-]2 (DPE2) is characterized by (1) its high affinity for receptors on NG108-15 hybrid cells, the affinity constantK=4.7×109 M–1 is up to 8-fold that of monomers (0.6 to 1.0×109 M–1), and (2) a maximal binding capacity equal to one half that of the monomers. Kinetic studies showed that DPE2 binds with a 2-fold higher rate, k1=6.3×107 M–1min–1, than monomers (2.4 to 3.8×107 M–1min–1), and dissociates at a slower rate than monomers. Dissociation of DPE2 was consistently bi- or multiphasic but increased about 12% only after 3 hr of dissociation in the presence of a large excess of unlabeled enkephalin. The dissociation kinetics of monomers varied with enkephalin and experimental conditions used. Consistent with the value for the maximal binding capacity, the kinetic studies are interpreted in support of the hypothesis that DPE2 binds by cross-linking two subunits of one receptor.  相似文献   

11.
A mutant strain of Penicillium citrinum grown in a chemically-defined production medium, yielded 145 mg compactin l–1. The medium also facilitated spectrophotometric analysis of compactin. Addition of KH2PO4in the production medium did not increase the compactin production, while addition of a surfactant, Tween 80, increased compactin to 175 mg l–1. Inoculation with 107 spores ml–1 and initial pH of 6.5–7 were the most suitable for compactin production.  相似文献   

12.
Summary This paper describes the effect of trinitrocresolate anions (TNC) on the electrical conductance (G m ), and tracer-measured unidirectional Na and K fluxes (M Na andM K) across bilayers formed from sheep red cell lipids dissolved in decane. In the absence of TNC, typical low conductances were observed, while the cation fluxes were too low to measure by our techniques (<10–12 moles cm–2 sec–1). In the presence of TNC (10–2 m),G m increased and TNC was the main charge carrier in the system. The cationic fluxes were also much increased, but the membranes showed no significant selectivity between K and Na. Furthermore, the Na and K fluxes were at least two orders of magnitude larger than the ionic fluxes calculated fromG m . Thus, almost all of the K and Na transport across the membrane in the presence of TNC is electrically silent and is probably carried out as KTNC and NaTNC ion pairs.In the presence of valinomycin (10–6 m) and no TNC, both the ion fluxes andG m were 103 times larger in KCl than in NaCl, thus exhibiting the characteristic high selectivity of valinomycin for K over Na. In the presence of both valinomycin (10–6 m) and TNC (10–2 m), this selectivity disappeared in that bothG m andM Na in the NaCl system were similar to the respective values in the KCl system. Even under these conditions, most of the Na is still transported by a process which does not carry charge.BothG m andM x increased alike and monotonically with increasing temperature over the range 7 to 30°C. In the absence of TNC the enthalpies of activation were invariably higher in KCl than in NaCl. Addition of TNC produced equal enthalpies of activation for both Na and K containing systems suggesting a common, temperature-dependent, ratedetermining step in charge transfer and the electrically silent cation fluxes.  相似文献   

13.
The inhibition by cupric ions of the hydration of CO2 catalyzed by carbonic anhydrase II is interesting because of the results of Tuet al. obtained at chemical equilibrium, indicating that Cu2+ inhibits specifically a proton transfer in the catalytic pathway. We have measured this inhibition at steady state, using stopped-flow methods. The inhibition by Cu2+ of the hydration of CO2 catalyzed by carbonic anhydrase II had aK I near 1×10–6 M atpH 7.0 and gave inhibition that is noncompetitive atpH 6.0 and mixed, but close to uncompetitive, atpH 6.8. ThepH dependence of this binding is consistent with a binding site for Cu2+ on the enzyme with apK a near 7. The binding interaction between Cu2+ and the fluorescent inhibitor 5-dimethylaminonaphthalene-l-sulfonamide on carbonic anhydrase II was noncompetitive, indicating that the binding site for Cu2+ is distinct from the coordination sphere of zinc in which the actual interconversion of CO2 and HCO 3 and the binding of sulfonamides takes place.  相似文献   

14.
The best culture medium composition for the production of bikaverin by Gibberella fujikuroi in shake-flasks, i.e. 100 g glucose l–1; 1 g NH4Cl l–1; 2 g rice flour l–1; 5 g KH2PO4 l–1 and 2.5 g MgSO4 l–1, was obtained through a fractional factorial design and then scaled-up to a fluidized bioreactor. The effects of carbon and nitrogen concentrations, inoculum size, aeration, flow rate and bead sizes on batch bikaverin production using immobilized G. fujikuroi in a fluidized bioreactor were determined by an orthogonal experimental design. Concentrations of up to 6.83 g bikaverin l–1 were obtained when the medium contained 100 g glucose l–1 and 1 g NH4Cl l–1 with an inoculum ratio of 10% v/v, an aeration rate of 3 volumes of air per volume of medium min–1, and a bead size of 3 mm. Based on dry weight, the bikaverin production was 30–100 times larger than found in submerged culture and approximately three times larger than reported for solid substrate fermentation.  相似文献   

15.
The prokaryotic algal symbiont of ascidians, Prochloron sp., was found to exhibit carbonic anhydrase activity which is largely associated with the cell surface. This extracellular carbonic anhydrase activity was inhibited, while the intracellular activity was not affected, by chloride or bromide. Acetazolamide and ethoxyzolamide inhibited carbonic anhydrase activity with I50 values of 7×10-4 and 3×10-4M, respectively. These I50 values are similar to those observed for intracellular carbonic anhydrases of Synechococcus sp. PCC7942, Chlamydomonas reinhardii and spinach.Abbreviations AZA acetazolamide - CA carbonic anhydrase - chl chlorophyll - EZA ethozyzolamide - I50 concentration of an inhibitor required to cause 50% inhibition - Rubisco ribulose-1,5-bisphosphate carboxylase/oxygenase - U unit  相似文献   

16.
Glutaminase-free l-asparaginase is known to be an excellent anticancer agent. In the present study, statistically based experimental designs were applied to maximize the production of glutaminase-free l-asparaginase from Pectobacterium carotovorum MTCC 1428. Nine components of the medium were examined for their significance on the production of l-asparaginase using the Plackett–Burman experimental design. The medium components, viz., glucose, l-asparagine, KH2PO4, and MgSO4·7H2O, were screened based on their high confidence levels (P < 0.04). The optimum levels of glucose, l-asparagine, KH2PO4, and MgSO4·7H2O were found to be 2.076, 5.202, 1.773, and 0.373 g L−1, respectively, using the central composite experimental design. The maximum specific activity of l-asparaginase in the optimized medium was 27.88 U mg−1 of protein, resulting in an overall 8.3-fold increase in the production compared to the unoptimized medium.  相似文献   

17.
Studies were conducted to elucidate the mechanism of action of 2-chloro-6-(trichloromethyl)pyridine or Technical N-SERVE on the nitrification process brought about byNitrosomonas europaea. The growth ofNitrosomonas was completely inhibited in the presence of 0.2 ppm N-SERVE while 1.0 ppm of the chemical was effective in the complete inhibition of ammonia oxidation by fresh cell suspensions. Cells stored at 4 C for a period of three days required somewhat higher concentrations (1.5 ppm) of N-SERVE for the complete inhibition of their ammonia oxidizing ability while the cytochrome oxidase of these cells was inhibited to the extent of 65 to 70 percent in the presence of a corresponding amount of N-SERVE. A 45 – 70 percent reversal of the inhibition of ammonia oxidation caused by N-SERVE was obtained by the addition of 6×10–4 M Cu++. An equivalent concentration of Cu++ was also effective for the complete reversal of the inhibition of cytochrome oxidase present in whole cells.Hydroxylamine oxidation by intactNitrosomonas cells was not affected by levels of N-SERVE ranging from 1 – 3 ppm. The cytochrome oxidase effective in hydroxylamine oxidation and present in cell-free extracts was not inhibited by even 100 ppm N-SERVE. Likewise, the hydroxylamine activating enzyme hydroxylamine cytochromec reductase was also not inhibited by such levels of the chemical. Raising the concentration to 170 ppm N-SERVE, however, caused a 90 percent inhibition of the enzyme.Although a 5×10–6 M concentration of allylthiourea completely inhibited ammonia oxidation byNitrosomonas cells, concentrations up to 10–3 M of this compound did not affect the cytochrome oxidase activity of whole cells or cell-free extracts. The inhibition of ammonia oxidation caused by 5×10–6 M allythiourea, unlike the inhibition by N-SERVE, could not be reversed by the addition of 6×10–4 M Cu++.Evidence is presented that the action of N-SERVE is on that component of cytochrome oxidase which is involved in ammonia oxidation.  相似文献   

18.
The abilities of various sorbents to adsorb catalase (CAT; EC 1.11.1.6) from filtered culture liquid (FCL) of the fungus Penicillium piceum F-648 were compared. Potassium phosphate, hydroxyapatite (HAP), and coprecipitated sorbents containing calcium phosphate and magnesium hydroxide adsorbed extracellular CAT more efficiently than aluminum oxide, aluminum phosphate, or quartz sand. The enzyme was isolated from FCL of Penicillium piceum with the use of HAP and a binary coprecipitated sorbent, Ca3(PO4)2 + Mg(OH)2, 1 : 1 (CM). The CAT(CM) sample contained the least amount of protein admixture. Its spectra had absorption maximums at 279.6, 406.8 (Soret band), 540, 585, 636, and 703 nm and negative molar ellipticity minimums at 207 and 210–214 nm. The kinetic indices of the samples (K M, V max : K M, and specific activity) were intricately dependent on the protein concentration in the reaction mixture. In dilute solutions, the K M and specific activities of CAT(CM) and CAT(HAP) equaled 667 and 137 mM; 300.9 × 104 and 30.0 × 104 U/mg protein, respectively. The effective velocity constants of inactivation of CAT(HAP), CAT(CM), and FCL in the reaction of H2O2 decomposition increased dramatically after the dilution of samples. In the infinitely dilute solution, they were 4.30 × 10–2, 6.46 × 10–2, and 1.12 × 10–2 s–1, respectively.  相似文献   

19.
Incorporation of ethanol (1.0 or 1.25 M) into exponential-phase cultures of Saccharomyces cerevisiae NCYC 366 growing anaerobically in a medium supplemented with ergosterol and an unsaturated fatty acid caused a retardation in growth rate, which was greater when the medium contained oleic rather than linoleic acid. Ethanol incorporation led to an immediate drop in growth rate, and ethanol-containing cultures grew at the slower rate for at least 10 h. Incorporation of ethanol (0.5 M) into buffered (pH 4.5) cell suspensions containing d-[6-3H] glucose, d-[1-14C] glucosamine, l-[U-14C] lysine or arginine, or KH2 32PO4 lowered the rate of solute accumulation by cells. Rates of accumulation of glucose, lysine and arginine were retarded to a greater extent when cells had been grown in the presence of oleic rather than linoleic acid. This difference was not observed with accumulation of phosphate. Ethanol was extracted from exponential-phase cells by four different methods. Cells grown in the presence of linoleic acid contained a slightly, but consistently, lower concentration of ethanol than cells grown in oleic acid-containing medium. The ethanol concentration in cells was 5–7 times greater than that in the cell-free medium.  相似文献   

20.
Summary We present a modification of Hansson's method for the demonstration of carbonic anhydrase activity. Using a semipermeable membrane together with a fluid incubation medium, frozen sections of aldehyde-fixed tissue were incubated without floating or dipping. Thin sections (thickness, 20–40 m) were mounted on the outer surface of a tubularshaped, semipermeable cellophane dialysis membrane containing the incubation fluid. After incubation for 25–30 min at room temperature, the sections were rinsed in buffer and treated with 0.5% (NH4)2S solution. The histochemical reaction was fully inhibited by 10–4 M acetazolamide.Dedicated to Professor Dr. T.H. Schiebler on the occasion of his 65th birthday  相似文献   

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