共查询到20条相似文献,搜索用时 15 毫秒
1.
The biopolymer emulsan, which forms stable emulsions with mixtures of aliphatic and cyclic (or aromatic) hydrocarbons in water, does not emulsify aliphatic hydrocarbons alone [1–4]. Monohydric primary alcohols from hexanol to dodecanol were shown to enhance the formation of pure aliphatic hydrocarbon/water emulsions under conditions of mild agitation. Enhancement was a function of emulsan concentration and was proportional to alkanol concentration (5×10–5 M to 2.5x10–4 M) at constant bioemulsifier concentration (0.05 mg/ml). Enhancement of emulsification was also found when aqueous solutions of diethanolamine and phenethyl alcohol (5 to 30×10–3 M) were substituted for the primary alcohols. None of these substances emulsified hexadecane or othern-alkanes in the absence of the biopolymer. The strongest enhancement of emulsification (3-fold) was observed with tetra- and hexadecane. At alkanol concentrations optimal for enhancement of emulsification, no significant lowering of hexadecane/ emulsan/water interfacial tension was observed. The possibility of a direct association of alkanols with the emulsan in solution, resulting in altered conformation of biopolymer and modification of its specificity toward hydrocarbons, is discussed.Preliminary results of this work were presented at the 57th Colloid and Surface Science Symposium, 1983, Toronto, Canada. 相似文献
2.
We have used the initial-rate approach to characterize changes in the glucose consumption kinetics of baculovirus-infected
Spodoptera frugiperda clone 9 (Sf9) cells with the progression of the infection process. The specific glucose consumption rate (q
G) of cultured baculovirus-infected Sf9 cells was measured at 4, 8, 12, 16, and 24 h postinfection (h.p.i.) in media containing
4–35 mM glucose. Higher medium glucose concentrations resulted in higher final extracellular virus and recombinant β-galactosidase
yields. q
G was related to the extracellular glucose concentration by means of a Michaelis-Menten relationship. The apparent Michaelis-Menten
constant (K
m) for glucose consumption was found not to change significantly during the progression of the infection process, and remained
between 6.2 and 7.2 mM. However, the maximal specific glucose consumption rate (q
Gmax) was found to rapidly increase after infection, peaking at 16 h.p.i. at a value four times that for uninfected Sf9 cells.
The kinetic analysis of glucose consumption rates in baculovirus-infected Sf9 cells presented here will aid in the optimal
design and operation of bioreactor systems for the large-scale production of recombinant products from the baculovirus/insect
cell system. 相似文献
3.
Joana R. Trindade Mara G. Freire Priscilla F.F. Amaral Maria Alice Z. Coelho Joo A.P. Coutinho Isabel M. Marrucho 《Colloids and surfaces. A, Physicochemical and engineering aspects》2008,324(1-3):149-154
The aging mechanisms of oil-in-water emulsions prepared with Yansan, a bioemulsifier produced by a Brazilian wild strain of Yarrowia lipolytica, IMUFRJ 50682, in glucose-based fermentation medium, were studied and compared with those prepared with Gum Arabic. Oil-in-water emulsions obtained by combining three different organic phases, perfluoro-n-hexane, n-hexadecane and toluene, with two aqueous buffers of different pH, and two bioemulsifiers, were studied through the evolution of the mean droplet size. The emulsions were prepared by sonication and their droplet size distribution was followed for 60 days at 301 K using image analysis. The results indicate that the aging mechanisms of the studied emulsions depend mainly on the bioemulsifier and on the pH of the medium. It is shown that the emulsions containing Gum Arabic age by coalescence while Yansan-based emulsions change their aging mechanisms from coalescence at pH 3 to molecular diffusion at pH 7. 相似文献
4.
The effects of sodium dodecyl sulfate on extracellular lipase produced byCandida lipolytica have been studied. The microorganism was grown in culture medium containing different sodium dodecyl sulfate concentrations
added to the culture at different intervals of growth. The extracellular lipase activity was not detected when the treated
culture supernatants were directly tested in Yeast Mold Agar-Triolein-Rhodamine plates, regardless of surfactant addition
time and concentrations. However, after ammonium sulfate precipitation and dialysis, the extracellular lipase activity could
be recovered. Therefore, the surfactant, under the experimental conditions used here, does not seem to be able to inhibit
lipase production, but it does inhibit the enzyme activity because of its presence in the mixture of the reaction. 相似文献
5.
Silva-Santisteban BO Converti A Filho FM 《Applied biochemistry and biotechnology》2009,152(2):249-261
Cultivations of Kluyveromyces marxianus var. bulgaricus ATCC 16045 were performed on both minimal and complex media using different carbon and nitrogen sources either in the presence
or absence of aeration. The results collected were worked out and compared so as to provide a useful contribution to the optimization
of inulinase production. Kinetics of extracellular inulinase release were similar on glucose, fructose, and sucrose. Inulinase
was detected at basal level since the beginning of batch runs on these three carbon sources and overproduced after their depletion.
The highest inulinase activity in minimal medium containing 10 g/l sucrose (6.4 IU/ml) was obtained at an initial (NH4)2SO4 concentration of 5 g/l, whereas it was reduced to about one fourth of this value and detected only at the beginning under
nitrogen-limited conditions. The best sucrose concentrations for the enzyme production were 30 and 20 g/l in minimal and complex
media, yielding 15.4 and 208 IU/ml, respectively. In general, the enzyme activity was much higher in complex than in minimal
medium under all conditions. O2-enriched air neither improved inulinase production nor prevented ethanol formation. 相似文献
6.
S. S. Deshmukh M. Dutta Choudhury V. Shankar 《Applied biochemistry and biotechnology》1993,42(2-3):95-104
Partially purified glucose isomerase fromStreptomyces thermonitrificans when coupled to glutaraldehyde-activated Indion 48-R, retained 30–40% activity of the soluble enzyme. However, an approximately
twofold increase in the activity could be achieved by binding the enzyme in the presence of glucose. Binding the enzyme to
matrices presaturated with either glucose or fructose and influence of lysine modification on the activity of the soluble
enzyme revealed that the comparatively low activity observed in case of the enzyme bound in the absence of substrate is the
result of the nonspecific binding of either substrate or product to the matrix. Immobilization did not affect the pH and temperature
optima of the enzyme, but it lowered the temperature stability. Immobilization resulted in a marginal increase in theK
m
and a threefold decrease in theV
max
. Substrate concentrations as high as 36% glucose could be converted to 18.5% fructose in 5 h, at pH 7.0 and 70‡C. The bound
enzyme, however, showed inferior stability to repeated use and lost approx 40% of its initial activity after five cycles of
use. Indion 48-R bound glucose isomerase could be stored, in wet state, for 30 d without any apparent loss in its initial
activity. 相似文献
7.
Konsoula Z Liakopoulou-Kyriakides M Perysinakis A Chira P Afendra A Drainas C Kyriakidis DA 《Applied biochemistry and biotechnology》2008,149(2):99-108
A hyperthermophilic α-amylase encoding gene from Pyrococcus woesei was transferred and expressed in Xanthomonas campestris ATCC 13951. The heterologous α-amylase activity was detected in the intracellular fraction of X. campestris and presented similar thermostability and catalytic properties with the native P. woesei enzyme. The recombinant α-amylase was found to be stable at 90 °C for 4 h and within the same period it retained more than
50% of its initial activity at 110 °C. Furthermore, X. campestris transformants produced similar levels of recombinant α-amylase activity regardless of the carbon source present in the growth
medium, whereas the native X. campestris α-amylase production was highly dependent on starch availability and it was suppressed in the presence of glucose or other
reducing sugars. On the other hand, xanthan gum yield, which appeared to be similar for both wild type and recombinant X. campestris strains, was enhanced at higher starch or glucose concentrations. Evidence presented in this study supports that X. campestris is a promising cell factory for the co-production of recombinant hyperthermophilic α-amylase and xanthan gum. 相似文献
8.
Cellulose is degraded during the growth of the cultivated mushroomA. bisporus on composted straw. At the time of sporophore enlargement, a marked increase in extracellular endocellulase activity occurs.
A high level of enzyme activity is maintained during subsequent cropping cycles.
Some of the factors affecting growth and production of extracellular endocellulase activity byA. bisporus cultured in simple defined liquid media have been examined. Endocellulase production by the fungus closely paralleled mycelial
growth in cultures containing microcrystalline cellulose. The enzyme was induced by various celluloses and cellobiose. In
the presence of a cellulose inducer, glucose and cellobiose repressed enzyme production.
Endocellulase activity in culture filtrates was inversely related to cellulose concentration in the culture. Although the
activity of free enzyme was low, in high concentrations of cellulose more cellulose was degraded. Evidence was obtained for
the existence of two forms of endocellulase activity. One form adsorbed strongly to cellulose and was predominant in cultures
low in cellulose. In cultures with a high cellulose content, a nonadsorbable form of the enzyme was more abundant.
It is suggested that the pattern of cellulase activities produced whenA. bisporus is grown on different concentrations of cellulose is partly accounted for by its adsorption to the cellulose. 相似文献
9.
Summary An extracellular lipase was produced by Bacillus coagulans by solid-state fermentation. Solid waste from melon was used as the basic nutrient source and was supplemented with olive
oil. The highest lipase production (78,069 U/g) was achieved after 24h of cultivation with 1% olive oil enrichment. Enzyme
had an optimal activity at 37°C and pH 7.0, and sodium dodecyl sulfate increased lipase activity. NH 4NO3 increased enzyme production, whereas organic nitrogen had no effect. The effect of the type of carbon sources on lipolytic
enzyme production was also studied. The best results were obtained with starch and maltose (148,932 and 141,629 U/g, respectively),
whereas a rather low enzyme activity was found in cultures grown on glucose and galactose (approx 118,769 and 123,622 U/g,
respectively). Enzyme was inhibited with Mn+2 and Ni+2 by 68 and 74%, respectively. By contrast, Ca+2 enhanced enzyme production by 5%. 相似文献
10.
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
11.
pH and temperature play critical roles in multistep enzymatic conversions. In such conversions, the optimal pH for individual
steps differs greatly. In this article, we describe the production of glucoamylase (from Aspergillus oryzae MTCC152 in solid-state fermentation) and glucose isomerase (from Streptomyces griseus NCIM2020 in submerged fermentation), used in industries for producing high-fructose syrup. Optimum pH for glucoamylase was
found to be 5.0. For glucose isomerase, the optimum pH ranged between 7.0 and 8.5, depending on the type of buffer used. Optimum
temperature for glucoamylase and glucose isomerase was 50 and 60°C, respectively. When both the enzymatic conversions were
performed simultaneously at a compromised pH of 6.5, both the enzymes showed lowered activity. We also studied the kinetics
at different pHs, which allows the two-step reaction to take place simultaneously. This was done by separating two steps by
a thin layer of urease. Ammonia generated by the hydrolysis of urea consumed the hydrogen ions, thereby allowing optimal activity
of glucose isomerase at an acidic pH of 5.0. 相似文献
12.
Summary The effect of some cationic detergents viz Phenyl Trimethyl Ammonium Chloride, Lauryl pyridinium chloride, Cetyl pyridinium
Bromide and Aerosol C-61, on the nujol/water emulsion stabilised by pepsin, has been studied. The detergents were added in
two ways: 1. before emulsification; 2. after emulsification. The results were compared by their flocculation concentrations
obtained at zero point of charge. From these values it is observed that the flocculation concentrations before emulsification
are higher than those obtained after emulsification. The stability of the present system is discussed in the light of DVO
theory. The high potential energy barriers obtained obviated the possibility of flocculation in primary minima. Therefore,
to explain the results, the flocculation was assumed to occur in the secondary minima. The flocculation studies were carried
out haemocytometrically which enabled to calculate the degrees of aggregation (D). In order to account for the observed values of D, the effective van der Waals constant of the system should be 1.0×10−12 erg. The binding parameters and free energies have also been calculated. 相似文献
13.
《Applied biochemistry and biotechnology》1996,131(1-3):864-869
Agrobacterium isolated from soil samples produced two extracellular polysaccharides: succinoglycan, an acidic soluble polymer, and curdlan
gum, a neutral, insoluble polymer. Maize glucose, cassava glucose, and maize maltose were used in fermentation medium to produce
insoluble polysaccharide. Two Agrobacterium sp. strains which were used (ATCC 31749 and IFO 13140) in the production of insoluble exopolysaccharide presented equal or
superior yields compared to the literature. The strain ATCC 31749 yielded better production when using maize maltose, whose
yield was 85%, whereas strain IFO 13140 produced more when fed maize glucose, producing a yield of 50% (on reducing sugars). 相似文献
14.
B. Szajáni Aranka Molnár Gabriella Klámar M. Kálmán 《Applied biochemistry and biotechnology》1987,14(1):37-47
A simple, one-step process, using 0.25Mp-benzoquinone dissolved in 20% dioxane at 50°C for 24 h was applied to the activation of polyacrylamide beads. The activated
beads were reacted with glucose oxidase isolated fromAspergillus niger. The coupling reaction was performed in 0.1M potassium phosphate at pH 8.5 and 0–4°C for 24 h. The protein concentration was
50 mg/mL. In such conditions, the highest activity achieved was about 100 U/g solid. The optimum pH for the catalytic activity
was shifted by about 1 pH unit in the acidic direction to pH 5.5. Between 35 and 50°C, the activity of the immobilized form
depends on the temperature to a smaller extent than that of the soluble form. Above 50°C, the activity of immobilized glucose
oxidase shows a sharper heat dependence. The enzyme-substrate interaction was not profoundly altered by the immobilization
of the enzyme. The heat resistance of the immobilized enzyme was enhanced. The immobilized glucose oxidase is most stable
at pH 5.5. The practical use of the immobilized glucose oxidase was tested in preliminary experiments for determination of
the glucose concentration in blood sera. 相似文献
15.
Julia Serkedjieva Svetla Danova Iskra Ivanova 《Applied biochemistry and biotechnology》2000,88(1-3):285-298
A novel antibacterial substance produced by Lactobacillus delbrueckii has been isolated and characterized (1). The inhibitory agent corresponded to the criteria for bacteriocins. It was active against lactic acid bacteria (LAB) species
and several food-borne pathogens. The cell-free supernatant was purified by HPLC gel-filtration. Three preparations at different
purification steps were tested for activity on the reproduction of influenza virus A/chicken/Germany, strain Weybridge (H7N7)
and strain Rostock (H7N1) in cell cultures of chicken embryo fibroblasts (CEF). The inhibitory effect was shown to be highly
selective and specific. Expression of viral glycoproteins hemagglutinin, neuraminidase, and nucleoprotein on the surface of
infected cells, virus-induced cytopathic effect, infectious virus yield, and hemagglutinin production were all reduced at
nontoxic concentrations of the crude preparation (B1). B1 did not protect cells from infection, did not affect adsorption,
and slightly inhibited viral penetration into infected cells. The purification did not enhance the cellular toxicity and increased
about 870-fold the virus-inhibitory activity. No inactivating effect on extracellular virus was found. 相似文献
16.
An extracellular xylanase produced by a Mexican Aspergillus strain was purified and characterized. Aspergillus sp. FP-470 was able to grow and produce extracellular xylanases on birchwood xylan, oat spelt xylan, wheat straw, and corncob,
with higher production observed on corncob. The strain also produced enzymes with cellulase, amylase, and pectinase activities
on this substrate. A 22-kDa endoxylanase was purified 30-fold. Optimum temperature and pH were 60°C and 5.5, respectively,
and isoelectric point was 9.0. The enzyme has good stability from pH 5.0 to 10.0 retaining >80% of its original activity within
this range. Half-lives of 150 min at 50°C and 6.5 min at 60°C were found. K
m
and activation energy values were 3.8 mg/mL and 26 kJ/mol, respectively, using birch wood xylan as substrate. The enzyme
showed a higher affinity for 4-O-methyl-d-glucuronoxylan with a K
m
of 1.9 mg/mL. The enzyme displayed no activity toward other polysaccharides, including cellulose. Baking trials were conducted
using the crude filtrate and purified enzyme. Addition of both preparations improved bread volume. However, addition of purified
endoxylanase caused a 30% increase in volume over the crude extract. 相似文献
17.
Luciano Belato Alves Graciette Matioli Flávio Faria De Moraes Gisella Maria Zanin José Eduardo Olivo 《Journal of inclusion phenomena and macrocyclic chemistry》2002,44(1-4):399-402
Different culture media have been testedfor the production of the enzyme CGTase (cyclodextringlycosyltransferase) from Bacillus firmus (strain #37). The concentration of different carbon and nitrogen sources have been varied and the enzyme activity, cell concentration, reducing sugars, total reducing sugars, soluble protein and pH have been followed during cultivation. Results indicate that higher concentrations of yeast extract and polypeptone lead to increased synthesis of CGTase, whereas when starch is substituted by glucose there is a drastic inhibition of CGTase production. 相似文献
18.
Dae Haeng Cho Hee Jeong Chae Eui Yong Kim 《Applied biochemistry and biotechnology》2001,95(3):183-193
The aim of this work was to characterize an exopolysaccharide by Rhodotorula glutinis KCTC 7989 and to investigate the effect of the culture conditions on the production of this polymer. The extracellular polysaccharide
(EPS) produced from this strain was a novel acidic heteropolysaccharide composed of neutral sugars (85%) and uronic acid (15%).
The neutral sugar composition was identified by gas chromatography as mannose, fucose, glucose, and galactose in a 6.7:0.2:0.1:0.1
ratio. The molecular weight of purified EPS was estimated to be 1.0−3.8×105 Dalton, and the distribution of the molecular weight was very homogeneous (polydispersity index =1.32). The EPS solution
showed a characteristic of pseudoplastic non-Newtonian fluid at a concentration >2.0% in distilled water. The maximum EPS
production was obtained when the strain was grown on glucose (30 g/L). Ammonium sulfate was the best suitable nitrogen source
for EPS production. The highest yield of EPS was obtained at a carbon to nitrogen ratio of 15. The EPS synthesis was activated
at the acidic range of pH 3.0–5.0 and increased when the pH of the culture broth decreased naturally to <2.0 during the fermentation.
When the yeast was grown on glucose (30 g/L) and ammonium sulfate (2 g/L) at 22°C at an initial pH of 4.0, EPS production
was maximized (4.0 g/L), and the glucose-based production yield coefficient and carbon-based production yield coefficient
were 0.30 g of EPS/g of glucose and 0.34 g (carbon of EPS)/g (carbon of glucose), respectively. 相似文献
19.
Byoung Chul Park Sukhoon Koh Changsoo Chang Se Won Suh Dae-Sil Lee Si Myung Byun 《Applied biochemistry and biotechnology》1997,62(1):15-27
The gene encoding xylose isomerase (xylA) was cloned fromThermus flavus AT62 and the DNA sequence was determined. ThexylA gene encodes the enzyme xylose isomerase (XI orxylA) consisting of 387 amino acids (calculated Mr of 44,941). Also, there was a partial xylulose kinase gene that was 4 bp overlapped
in the end of XI gene. The XI gene was stably expressed inE. coli under the control oftac promoter. XI produced inE. coli was simply purified by heat treatment at 90°C for 10 min and column chromatography of DEAE-Sephacel. The Mr of the purified
enzyme was estimated to be 45 kDa on SDS-polyacrylamide gel electrophoresis. However, Mr of the cloned XI was 185 kDa on native
condition, indicating that the XI consists of homomeric tetramer. The enzyme has an optimum temperature at 90°C. Thermostability
tests revealed that half life at 85°C was 2 mo and 2 h at 95°C. The optimum pH is around 7.0, close to where by-product formation
is minimal. The isomerization yield of the cloned XI was about 55% from glucose, indicating that the yield is higher than
those of reported enzymes. The Km values for various sugar substrates were calculated as 106 mM for glucose. Divalent cations
such as Mn2+, Co2+, and Mg2+ are required for the enzyme activity and 100 mM EDTA completely inhibited the enzyme activity. 相似文献
20.
The fermentation characteristics of a recombinant strain of Zymomonas mobilis ZM4(pZB5) capable of converting both glucose and xylose to ethanol have been further investigated. Previous studies have
shown that the strain ZM4(pZB5) was capable of converting a mixture o 65 g/L of glucose and 65 g/L of xylose to 62 g/L of
ethanol in 48 h with an overall yield of 0.46 g/g. Higher sugar concentrations (e.g., 75/75 g/L) resulted in incomplete xylose
utilization (80 h). In the present study, further kinetic evaluations at high sugar levels are reported. Acetate inhibition
studies and evaluation of temperature and pH effects indicated increased maximum specific uptake rates of glucose and xylose
under stressed conditions with increased metabolic uncoupling. A high-productivity system was developed that involved a membrane
bioreactor with cell recycling. At sugar concentrations of approx 50/50 g/L of glucose/xylose, an ethanol concentration of
50 g/L, an ethanol productivity of approx 5 g/(L·h), and a yield (Y
p/s) of 0.50 g/g were achieved. Decreases in cell viability were found in this system after attainment of an initial steady state
(40–60 h); a slow bleed of concentrated cells may be required to overcome this problem. 相似文献