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1.
The effect of additives on welan gum production produced by fermentation with Alcaligenes sp. CGMCC2428 was studied. Tween-40 was the best additive for improving welan gum production and welan gum displayed better rheological properties than that obtained by control fermentation without additives. Response surface methodology was employed to optimize the culture conditions for welan gum production in the shake flask culture, including Tween-40 concentration, pH and culture temperature. The optimal conditions were determined as follows: Tween-40 concentration 0.94 g/l, pH 6.9 and temperature 29.6 °C. The corresponding experimental concentration of welan gum was 23.62 ± 0.60 g/l, which was agreed closely with the predicted value (23.48 g/l). Validation experiments were also carried out to prove the adequacy and the accuracy of the model obtained. The welan gum fermentation in a 7.5 l bioreactor reached 24.90 ± 0.68 g/l.  相似文献   

2.
Wu M  Tang C  Li J  Zhang H  Guo J 《Carbohydrate research》2011,(14):2149-2155
A parent strain Aspergillus niger LW-1 was mutated by the compound mutagenesis of vacuum microwave (VMW) and ethyl methane sulfonate (EMS). A mutant strain, designated as A. niger E-30, with high- and stable-yield β-mannanase was obtained through a series of screening. The β-mannanase activity of the mutant strain E-30, cultivated on the basic fermentation medium at 32 °C for 96 h, reached 36,675 U/g dried koji, being 1.98-fold higher than that (18,501 U/g dried koji) of the parent strain LW-1. The purified E-30 β-mannanase, a glycoprotein with a carbohydrate content of 19.6%, had an apparent molecular weight of about 42.0 kDa by SDS–PAGE. Its optimal pH and temperature were 3.5 and 65 °C, respectively. It was highly stable at a pH range of 3.5–7.0 and at a temperature of 60 °C and below. The kinetic parameters Km and Vmax, toward locust bean gum and at pH 4.8 and 50 °C, were 3.68 mg/mL and 1067.5 U/mg, respectively. The β-mannanase activity was not significantly affected by an array of metal ions and EDTA, but strongly inhibited by Ag+ and Hg2+. In addition, the hydrolytic conditions of konjak glucomannan using the purified E-30 β-mannanase were optimized as follows: konjak gum solution 240 g/L (dissolved in deionized water), hydrolytic temperature 50 °C, β-mannanase dosage 120 U/g konjak gum, and hydrolytic time 8 h.  相似文献   

3.
Summary Aerobic decomposition of tylosin fermentation waste was studied by O2 uptake and CO2, NH4 + and NO3 release over 10 weeks in a light compost-soil at 3 concentrations and 4 temperatures. Comparisons of O2 uptake and CO2 release at each temperature showed that aerobic conditions were maintained in the system. Maximal rates of respiration (C mineralization) increased with temperature. At 23°C 50% of the substrate C had been mineralized in 10 weeks. At 10–15°C and at 4°C C mineralization was approximately 38% and 22% respectively. Except at 4°C mineralization had almost ceased within 10 weeks. There was evidence of a permanent inhibition of C mineralization at 10–15°C compared with 23°C, and a temporary inhibition at 10°C compared with 15°C.At 10 weeks 25% of the N had been mineralized at 23, 15 and 10°C, while 14% had been mineralized at 4°C. The time taken to reach maximum N mineralization was reduced by increase in temperature and by 10 weeks mineralization had almost ceased at 15 and 23°C. In terms of the fertilizing effect of tylosin fermentation, 25% of the total N was available within 10 weeks at 10–23°C. Nitrification was strongly inhibited at 4 and 10°C. Both C and N mineralization were in direct proportion to the concentration of tylosin fermentation waste added to the soil.  相似文献   

4.
A thermostable superoxide dismutase (SOD) from a Thermomyces lanuginosus strain (P134) was purified to homogeneity by fractional ammonium sulfate precipitation, ion-exchange chromatography on DEAE-Sepharose, Phenyl-Sepharose hydrophobic interaction chromatography, and gel filtration on Sephacryl S-100. The molecular mass of a single band of the enzyme was estimated to be 22.4 kDa, using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Using gel filtration on Sephacryl S-100, the molecular mass was estimated to be 89.1 kDa, indicating that this enzyme was composed of four identical subunits of 22.4 kDa each. The SOD was found to be inhibited by NaN3, but not by KCN or H2O2, suggesting that the SOD in T. lanuginosus was of the manganese superoxide dismutase type. The SOD exhibited maximal activity at pH 7.5. The optimum temperature for the activity was 55°C. It was thermostable at 50 and 60°C and retained 55% activity after 60 min at 70°C. The half-life of the SOD at 80°C was approximately 28 min and even retained 20% activity after 20 min at 90°C.  相似文献   

5.
Summary The fermentation of glucose byClostridium thermosaccharolyticum strains IMG 2811T, 6544 and 6564 was studied in batch culture in a complex medium at different temperatures in defined and free-floating pH conditions. All the strains ferment 5 g glucose.l–1 completely. The yield of the fermentation products turned out to be independent of the incubation temperature for strain IMG 2811T. Strain IMG 6544 produced at 60°C significantly more ethanol and less acetic acid, butyric acid, hydrogen gas and biomass than at lower temperatures. With strain IMG 6564, the opposite effect occurred: ethanol appeared to be the main fermentation product at 45°C; at 60°C less ethanol and more acetic acid, butyric acid and hydrogen gas was formed.Experiments, carried out with strain IMG 6564, at defined pH conditions (between 5.5 and 7) and different temperatures (45, 55 and 60°C) revealed no effect of the incubation temperature, but an important effect of the pH on the product formation. At pH 7, ethanol was the main fermentation product while minor amounts of hydrogen gas, acetic and butyric acid were produced. Lowering the pH gradually to 5.5 resulted in a decrease of ethanol and an increase of biomass, hydrogen gas, acetic, butyric and lactic acids. At pH higher than 7 no growth occurred. Similar conclusions could be drawn for strains IMG 2811T and 6544.  相似文献   

6.
Summary Phage lambda pL promoter controlled expression of theBacillus stearothermophilus gene coding for a thermostable -amylase inE. coli was studied in shake flask cultures and in a laboratory fermenter. At an inducible temperature (40 °C) the final cell density was lower, but the total enzyme activity produced ca. 80% higher than at a non-inducible temperature (30 °C). Moreover, 17% of the total enzyme activity was found in the culture medium. The -amylase yield, production rate and proportion secreted were further increased by shifting the fermentation temperature after certain period of bacterial growth rather than at the beginning of fermentation.  相似文献   

7.
Male Guinea pigs (n=80) were divided into four groups and maintained in a climatic chamber for three weeks in one of the following environmental conditions: (1) Ta20°C and 55% RH; (2) Ta35°C and 30–35% RH from 08:00 to 20:00 h and 5°C; 60–65% RH, from 20:00 h to 08:00 h; (3) Ta5°C and 60–65% RH; (4) Ta35°C and 30–35% RH. At the end of this period the animals were exposed to either –5°C, 60–65% RH or 45°C, 30–35% RH, for a period of 20 min, following which Tre, plasma 11-OHCS, thyroxin, glucose, and FFA, and body and organ weights were determined. The cold-warm adapted animals seemed to develop a more efficient adaptability to acute heat and cold exposure. It is suggested that on acute exposure to severe environmental conditions the endocrine and the nervous system play a dominant role in maintaining optimal body temperature, while on chronic exposure the metabolic rate of the various organs becomes relatively more important.  相似文献   

8.
Recombinant alkaline phosphatase expressed in insect cells was concentrated 1.5 times by hydrogel ultrafiltration by swelling at 20°C and collapsing at 35°C at 53-65% separation efficiency and 78-83% enzyme recovery. Enzyme entrapment between gel particles and attachment of enzymes to the gel surface was the main reason for the poor separation efficiency and low enzyme recovery. Exposure of the enzyme at the collapse temperature during repeated swelling-collapsing cycles also decreased separation efficiency to 37% due to thermal deactivation of the enzyme.  相似文献   

9.
Summary A fungal isolate identified asRhizopus oryzae, produces an extracellular alkaline serine protease. Maximum protease formation was after six days in shake flask culture at two different conditions of pH and temperature optimum (pH 5 at 30°C and pH 10 at 37°C). AgNO3 and Tween 80 increased protease synthesis. The enzyme is stable between pH 3 and pH 11 and has a temperature optimum of 60°C.  相似文献   

10.
Extracellular cellulolytic and xylanolytic enzymes ofStreptomyces sp. EC22 were produced during submerged fermentation. The cell-free culture supernatant of the streptomycete grown on microcrystalline cellulose contained enzymes able to depolymerize both crystalline and soluble celluloses and xylans. Higher cellulase and xylanase activities were found in the cell-free culture supernatant of the strain when grown on microcrystalline cellulose than when grown on xylan. Total cellulase and endoglucanase [carboxymethyl-cellulase (CMCase)] activities reached maxima after 72 h and xylanase activity was maximal after 60h. Temperature and pH optima were 55°C and 5.0 for CMCase activity and 60°C and 5.5 for total crystalline cellulase and xylanase activities. At 80°C, approximate half-lives of the enzymes were 37, 81 and 51 min for CMCase, crystalline cellulose depolymerization and xylanase, respectively.  相似文献   

11.
The solution properties of κ-carrageenan and κ-carrageenan/locust bean gum mixtures have been studied by small deformation oscillation measurements and differential scanning calorimetry (DSC) in the presence of sodium chloride and sodium iodide. Both salts induced the κ-carrageenan to undergo a coil-helix conformational change as noted by an increase in the storage and loss moduli (G′, G′) and by an exothermic peak in the DSC cooling curves. The enthalpy ΔHc-h and temperature of the conformational transition Tc-h were higher in Nal compared to NaCl and Tc-h increased with increasing the concentration of both electrolytes. Gelation was not observed for carrageenan or carrageenan/locust bean gum mixtures in the presence of up to 200 mM Nal. Although carrageenan alone did not gel in the presence of 100 mM NaCl, a weak gel was obtained for a mixture containing 0.9%/0.1% carrageenan/locust bean gum. Furthermore, the mixture showed hysteresis in both the rheological and DSC cooling and heating curves. A strong gel was produced for carrageenan alone in the presence of 200 mM NaCl and the gel strength increased on adding a small proportion of locust bean gum (0.9%/0.1%). © 1997 John Wiley & Sons, Inc. Biopoly 41: 657–671, 1997  相似文献   

12.
We examined hydrogen production from a dairy cow waste slurry (13.4 g of volatile solids per liter) by batch cultures in a temperature range from 37 to 85°C, using microflora naturally present within the slurry. Without the addition of seed bacteria, hydrogen was produced by simply incubating the slurry, using the microflora within the slurry. Interestingly, two peaks of fermentation temperatures for hydrogen production from the slurry were observed at 60 and 75°C (392 and 248 ml H2 per liter of slurry, respectively). After the termination of the hydrogen evolution, the microflora cultured at 60°C displayed hydrogen-consuming activity, but hydrogen-consuming activity of the microflora cultured at 75°C was not detected, at least for 24 days. At both 60 and 75°C, the main by-product was acetate, and the optimum pH of the slurry for hydrogen production was around neutral. Bacteria related to hydrogen-producing moderate and extreme thermophiles, Clostridium thermocellum and Caldanaerobacter subterraneus, were detected in the slurries cultured at 60 and 75°C, respectively, by denaturing gradient gel electrophoresis analyses, using the V3 region of 16S rDNA.  相似文献   

13.
The effect of temperature and oxygen on diazotrophic growth of the thermophilic cyanobacterium HTF (High Temperature Form) Chlorogloeopsis was investigated using cells grown in light-limited continuous culture at a dilution rate of 0.02 h-1. Diazotrophy was more sensitive to elevated temperatures than growth with combined nitrogen. The maximum temperature for growth of cultures gassed with CO2-enriched air was more than 55 °C but less than 60 °C with N2 as the sole nitrogen source, but between 60°C and 65°C when nitrate was present in the medium. The effect of temperature on nitrogenase activity, photosynthesis and respiration in the dark was determined using cells grown at 55°C. Maximal rates of all three processes were observed at 55°C and rates at 60°C during shortterm incubations were not less than 75% of the maximum. However, nitrogenase activity at 60°C was unstable and decayed at a rate of 2.2 h-1 under air and at 0.3 h-1 under argon. Photosynthesis and respiration were more stable at 60°C than anoxic nitrogen fixation. The upper temperature limits for diazotrophic growth thus seem to be set by the stability of nitrogenase.Abbreviations chl chlorophyll a - DCMU N-(3,4-dichlorophenyl) N,N-dimethylurea - Taps N-tris(hydroxymethyl)methyl-3-aminopropanesulfonic acid  相似文献   

14.
Tsevdou MS  Taoukis PS 《Anaerobe》2011,17(6):456-458
High Hydrostatic Pressure (HP) processing has been suggested as an alternative method to improve textural attributes of dairy products. Since, the global market seeks improved functional foods, it is important to investigate whether HP processing can be applied to fermented dairy probiotic products. The inactivation kinetics of Bifidobacterium spp. in a model system of acid pH value under high pressure (100–400 MPa) combined with moderate temperature (20–35 °C) was investigated. Bifidobacterium spp. inactivation followed first order kinetics at all pressure–temperature combinations used. Pressure and temperature were found to act synergistically on the viability loss of the bacterium. The corresponding zT and zP values of inactivation were also estimated and, values of 41.5 °C and 93.5 MPa at reference pressure of 200 MPa and reference temperature of 25 °C were estimated, respectively. HP treatment of 200 MPa at 20–25 °C for 10–15 min, recommended for textural modification, is not detrimental to the viability of the studied probiotic culture and would be suitable for respective fermented probiotic products.  相似文献   

15.
Summary The influence of light intensity and temperature on the diurnal course and magnitude of CO2 gas exchange and on acid metabolism was studied in the laboratory with rooted rosettes of Sempervivum montanum collected at 2,200 m above sea level in the Central Alps. Under a temperature regime having a cool dark period and warm light period, S. montanum exhibited the time course of CO2 gas exchange typical of a CAM plant; the response was very distinct even when the plants were well-watered. At day temperatures of less than 10° C and at night temperatures greater than 35° C, S. montanum behaved like a C3 plant. Characteristic for S. montanum are a broad temperature optimum and a wide range of temperatures in which CO2 uptake in light is possible (-2° to 45° C). Dark fixation of CO2 is evident between-2° and 35° C, an apparent uptake of external CO2, on the other hand, only as high as 20° C. Light saturation of CO2 uptake is reached at 60–80 W m-2 while the rate of deacidification is nearly maximal at 40 W m-2. These results show that, due to their specific metabolism, CAM plants can be favored not only in xeric habitats, but also in heat stressed mountain habitats where the daily variation in temperature may be extreme.Dedicated with appreciation to Dr. K.F. Springer  相似文献   

16.
Summary At temperatures of 20°, 30°, 40°, 50° and 60°C in a Gangetic alluvial soil (G soil, pH 7.6) N-mineralization and nitrification increased with temperature up to 40°C and mineralized N accumulated entirely as nitrate. At 50° and 60°C mineralized N was relatively low and no nitrification occurred. In the Red soil (R soil, pH 5.2) mineralized N increased with temperature up to 40°C, was somewhat less at 50°C and was at a maximum at 60°C. Nitrification was maximum at 30°C but did not occur at 50° and 60°C. In the G soil C-mineralization increased considerably with temperature, whilst in the R soil there were only small differences due to temperature.  相似文献   

17.
Summary A method for the quantitative measurement of the maximum growth rate (m) of hydrogen-consuming methanogenic populations was applied to assess the toxicity of ammonia1 under various pH and temperature conditions. The maximum uninhibited growth rate of the hydrogenotrophic population present in sludge from an industrial anaerobic wastewater treatment system appeared to be 0.126 h-1 at pH=7 and 37°C. At 350 mM ammonia the maximum growth rate had decreased to almost half that value. At a temperature of 29°C the maximum growth rates in the ammonia range tested appeared to be approximately 60% of that at 37°C, while increasing ammonia concentrations caused a similar maximum growth rate decline. At 37°C an increase of the pH to 7.8 appeared to enhance ammonia inhibition of the maximum growth rate. Increased propionate concentrations (tested up to 60 mM) appeared to have no effect on ammonia inhibition.  相似文献   

18.
Summary A cell entrapment process using -carrageenan — locust bean gum gel is presented. Streptococcus thermophilus, Lactobacillus bulgaricus and S. lactis were immobilized in small gel beads (0.5–1.0 mm and 1.0–2.0 mm diameter) and fermentations in bench bioreactors were conducted. Viability of entrapped cells, lactose utilization, lactic acid production and cell release rates were measured during fermentation. The procedure was effective for S. thermophilus, L. bulgaricus and S. lactis, and the viability of these bacteria remained very high throughout entrapment steps and subsequent storage. Bead diameter influenced the fermentation rate: smaller beads (0.5–1.0 mm) permitted an increase in release rates, lactose utilization and acid production by entrapped cells, approximating values attained with free cells.  相似文献   

19.
Novel carboxymethyl guar gum (CMG)-chemically modified multiwalled carbon nanotube (MCNT) hybrid hydrogels were synthesized at different MCNT levels as potential device for sustained trans-dermal release of diclofenac sodium. Spectroscopy together with morphology, thermogravimetry, and rheological studies proved relatively strong CMG-MCNT interaction at 0.5 and 1 wt% levels of MCNT whereas de-wetting was increased with higher MCNT concentration. Drug encapsulation tendency increased with addition of MCNT; maximum entrapment was noticed at 1 wt% MCNT level. Hydrogels containing 0.5, 1 and 3 wt% MCNT exhibited slower trans-dermal release than neat CMG due to slightly higher gel viscosity and more drug entrapment. Slowest but steady release was obtained from 1 wt% MCNT loaded hydrogel due to highest viscous resistance among all other hybrid nanocomposites.  相似文献   

20.
Continental and submarine solfataric fields turned out to contain various extremely thermophilic anaerobic organisms which all belong to the archaebacteria. They are living autotrophically on sulphur, hydrogen and CO2 or by methanogenesis or heterotrophically on different organic substrates by sulphur respiration or, less frequently, by fermentation. The most extremely thermophilic isolates are growing between 80 and 110°C with an optimum around 105°C.  相似文献   

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