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1.
The growth and level of xanthophylls of several representative species of green algae were investigated as a possible source of pigmentation for the egg yolk and broiler markets. Chlorella pyrenoidosa 7-11-05 was selected for fermentation studies because of its high level of xanthophylls and wide temperature range for growth. The heterotrophic metabolism was preferred because of the ease of adaptability to present fermentation equipment. When used as the sole carbon source, glucose was the only sugar, among many tested, that gave appreciable growth in illuminated shaken flasks. A dry cell weight of 90 g per liter and total xanthophylls of 450 mg per liter were obtained from 190 g per liter of glucose monohydrate in 168-hr illuminated shaken flasks. Higher levels of glucose decreased yields. In combination with glucose, monosaccharides, such as fructose and galactose, were readily assimilated. The 7-11-05 strain was adapted to galactose as the sole carbon source after six vegetative passages. Light of the proper intensity and duration stimulated total xanthophylls approximately 35%. The effect on dry cell weight and total xanthophylls of seven antibiotics added at various levels in shaken flasks was studied. Erythromycin was essentially stable throughout the fermentation and nontoxic up to 25 μg/ml, with only slight toxicity at higher levels. Both erythromycin and ristocetin were effective in controlling a high incidence of bacterial contamination in 30-liter fermentors. With the higher agitation and aeration rates possible in 30-liter fermentors, dry cell weights in excess of 100 g per liter and total xanthophylls of 467 to 512 mg per liter were readily obtained from 230 to 260 g per liter of glucose in 162-hr illuminated batch-type fermentations. Continuous-feed runs yielded a dry cell weight of 302 g per liter and total xanthophylls of 650 mg per liter from 520 g per liter of glucose. The type of Chlorella cell produced was an important consideration with respect to the availability of the xanthophylls in pigmenting egg yolks and broilers.  相似文献   

2.
A method for the anaerobic growth of Thiobacillus denitrificans in a 140-liter (total capacity) stainless-steel culture vessel is described. As a result of controlling the pH value of cultures, and of ensuring that certain essential nutrients were in excess, cell yields approaching 700 mg (dry weight) per liter were obtained. These were over threefold higher than the best yields hitherto reported. The average rhodanese content of the cells from four cultures was 176,000 units per gram (dry weight). Adenosine-5′-phosphosulfate reductase (average content, 238 units per gram dry weight) and adenylate kinase (average content, 15,300 units per gram, dry weight) were also present.  相似文献   

3.
Growth of Bacteroidaceae in Stirred Fermentors   总被引:4,自引:2,他引:2       下载免费PDF全文
The conditions for increasing bacterial yields in cultures of Bacteroidaceae by the use of stirred fermentors and pH control were investigated by means of three representative species: Sphaerophorus necrophorus, Bacteroides fragilis, and B. melaninogenicus. A medium containing tryptone, yeast extract, and glucose or sucrose was used. Horse serum had to be added to obtain substantial growth of B. melaninogenicus. The optimal pH for growth rate and yield was 7.0 to 7.2. Lysis of the bacteria occurred when the glucose (or sucrose) was exhausted. The rate of lysis was very high in cultures of S. necrophorus, less so in B. fragilis and B. melaninogenicus. Pleomorphism, manifested as large sperical forms of the bacteria, was observed in the late logarithmic phase of S. necrophorus. Great differences in the length of the lag phase and of the mean generation time were found among the three bacterial species. The yield in static cultures of the three species without pH control was approximately 0.4 g of dry cells per liter, but was increased, in stirred fermentors with pH control, to 3.5 g (S. necrophorus), 2.7 g (B. fragilis), and 4.3 g (B. melaninogenicus) per liter. With an inoculum density of 5 to 10 mg (dry weight) per liter, these yields were obtained in approximately 10 (S. necrophorus), 25 (B. fragilis), and 35 hr (B. melaninogenicus), respectively.  相似文献   

4.
The applicability of a new aeration-agitation type fermentor with a grid-paddle type impeller and a spiral-sparger, Maxblend Fermentor® (MBF) for high density cultivation of plant cells, was investigated. The MBF showed a high capacity for oxygen supply and extremely low hydrodynamic stress in aeration and mixing compared with a conventional fermentor (CF). When Oryza sativa cells were cultivated at a kLa of 20 h−1, a high cell density cultivation of about 30 g dry cell weight per liter was accomplished in both fermentors and there were few differences in culture performance between the two. On the contrary, considerable differences were observed when Catharanthus roseus cells, which seemed to be sensitive to physical stress, were cultivated at a kLa of 20 h−1 in both fermentors. The MBF exhibited excellent cell growth characteristics, achieving about 19 g dry cell weight per liter, because of its superior oxygen supply and low hydrodynamic stress in aeration and mixing in highly viscous cultures containing high density cells. In CF only about 9.5 g dry cell weight per liter was achieved because of its high hydrodynamic stress.  相似文献   

5.
The effect of CO2 availability on cell size, shape, and aggregation in continuous cultures of Candida utilis was studied in minimal medium with glucose or ethanol as the sole carbon and energy source. Enrichment with CO2 was achieved (i) by using the substrate with more C atoms, (ii) by using pure oxygen and thus decreasing aeration intensity at the same dissolved-oxygen concentration, or (iii) by adding CO2 to the aeration gas. The cells were always of yeast shape, and no filaments were formed. In cultures with a biomass concentration above 6 g (dry weight) per liter, no cell aggregates were observed. In cultures with a lower biomass, the daughter cells failed to separate from the parent cells and formed aggregates with thickened walls. The average cell number per aggregate was found to be higher, and the average protoplast volume lower, under conditions of probable CO2 limitation. Simultaneously, the ratio of total dry weight to wet weight of protoplasts was considerably higher, indicating an increased share of wall or extracellular material. The possible effect of the observed morphological changes for maintaining a suitable concentration gradient of CO2 around the cell is discussed.  相似文献   

6.
花生四烯酸高产菌株的选育   总被引:18,自引:0,他引:18  
本研究以一株能产生花生四烯酸的被孢霉菌为出发菌株,通过紫外线诱变筛选出一株高产花生四烯酸的突变株M10,发酵试验结果表明:突变株M10的每升培养液中干菌体得率为31g,油脂含量为8.3g,而原菌株仅为20.3g和5.4g,气相色谱分析结果M10所产花生四烯酸的量占总脂的10.06%(0.83g/L培养液)。同时对M10菌株的生长和发酵特性及发酵过程中菌丝体形态变化作了一定的探讨。  相似文献   

7.
The effect of CO2 availability on cell size, shape, and aggregation in continuous cultures of Candida utilis was studied in minimal medium with glucose or ethanol as the sole carbon and energy source. Enrichment with CO2 was achieved (i) by using the substrate with more C atoms, (ii) by using pure oxygen and thus decreasing aeration intensity at the same dissolved-oxygen concentration, or (iii) by adding CO2 to the aeration gas. The cells were always of yeast shape, and no filaments were formed. In cultures with a biomass concentration above 6 g (dry weight) per liter, no cell aggregates were observed. In cultures with a lower biomass, the daughter cells failed to separate from the parent cells and formed aggregates with thickened walls. The average cell number per aggregate was found to be higher, and the average protoplast volume lower, under conditions of probable CO2 limitation. Simultaneously, the ratio of total dry weight to wet weight of protoplasts was considerably higher, indicating an increased share of wall or extracellular material. The possible effect of the observed morphological changes for maintaining a suitable concentration gradient of CO2 around the cell is discussed.  相似文献   

8.
The methylotrophic yeast Pichia methanolica can be used to express recombinant genes at high levels under the control of the methanol-inducible alcohol oxidase (AUG1) promoter. Methanol concentrations during the induction phase directly affect cellular growth and protein yield. Various methanol concentrations controlled by an on-line monitoring and control system were investigated in mixed glucose/methanol fed-batch cultures of P. methanolica expressing the human transferrin N-lobe protein. The PMAD18 P. methanolica strain utilized is a knock-out for the chromosomal AUG1 gene locus, resulting in a slow methanol utilization phenotype. Maximum growth of 100 g of dry cell weight per liter of culture was observed in cultures grown at 1.0% (v/v) methanol concentration. Maximum recombinant gene expression was observed for cultures controlled at 0.7% (v/v) methanol concentration, resulting in maximum volumetric production of 450 mg of transferrin per liter after 72 h of elapsed fermentation time.  相似文献   

9.
以表达普鲁兰酶的重组大肠杆菌作为出发菌株,在摇瓶培养的基础上,建立了大肠杆菌工程菌产普鲁兰酶的高密度发酵工艺。通过测定细胞密度、细胞干重、分离菌体可溶性成分与不溶性成分及SDS-PAGE电泳,分析重组大肠杆菌的生长和普鲁兰酶的表达情况。摇瓶试验使用合成培养基和LB培养基,重组大肠杆菌在合成培养基生长较慢,诱导5 h的普鲁兰酶表达量高于LB培养基,包涵体比例低于LB培养基。重组大肠杆菌的高密度发酵使用合成培养基,补料阶段采用指数流加的工艺,在设定细胞的比生长速率为0.12的前提下,限制补料中碳源的供应,以阻止乙酸的产生。当细胞密度OD600达到70.0开始诱导,最终细胞密度为每升53.3 g细胞干重,细胞内可溶性普鲁兰酶为每升1.35 g。  相似文献   

10.
Alcaligenes latus has been known to produce poly(3-hydroxybutyrate) (PHB) in a growth-associated manner even under nutrient-sufficient conditions. However, the PHB content obtained by fed-batch culture was always low, at ca. 50%, which makes the recovery process inefficient. In this study, the effect of applying nitrogen limitation on the production of PHB by A. latus was examined. In flask and batch cultures, the PHB synthesis rate could be increased considerably by applying nitrogen limitation. The PHB content could be increased to 87% by applying nitrogen limitation in batch culture, which was considerably higher than that typically obtainable (50%) under nitrogen-sufficient conditions. In fed-batch culture, cells were first cultured by the DO-stat feeding strategy without applying nitrogen limitation. Nitrogen limitation was applied at a cell concentration of 76 g (dry cell weight)/liter, and the sucrose concentration was maintained within 5 to 20 g/liter. After 8 h of nitrogen limitation, the cell concentration, PHB concentration, and PHB content reached 111.7 g (dry cell weight)/liter, 98.7 g/liter, and 88%, respectively, resulting in a productivity of 4.94 g of PHB/liter/h. The highest PHB productivity, 5.13 g/liter/h, was obtained after 16 h.  相似文献   

11.
The potential of Pseudomonas pseudoflava to produce poly-beta-hydroxyalkanoates (PHAs) from pentoses was studied. This organism was able to use a hydrolysate from the hemicellulosic fraction of poplar wood as a carbon and energy source for its growth. However, in batch cultures, growth was inhibited completely at hydrolysate concentrations higher than 30% (vol/vol). When P. pseudoflava was grown on the major sugars present in hemicelluloses in batch cultures, poly-beta-hydroxybutyric acid (PHB) accumulated when glucose, xylose, or arabinose was the sole carbon source, with the final PHB content varying from 17% (wt/wt) of the biomass dry weight on arabinose to 22% (wt/wt) of the biomass dry weight on glucose and xylose. Specific growth rates were 0.58 h on glucose, 0.13 h on xylose, and 0.10 h on arabinose, while the specific PHB production rates based on total biomass ranged from 0.02 g g h on arabinose to 0.11 g g h on glucose. PHB weight-average molecular weights were 640,000 on arabinose and 1,100,000 on glucose and xylose. The absolute amount of PHB in the cells decreased markedly when nitrogen limitation was relaxed by feeding ammonium sulfate at the end of the PHB accumulation stage of the arabinose and xylose fermentations. Copolymers of beta-hydroxybutyric and beta-hydroxyvaleric acids were produced when propionic acid was added to shake flasks containing 10 g of glucose liter. The beta-hydroxyvaleric acid monomer content attained a maximum of 45 mol% when the initial propionic acid concentration was 2 g liter.  相似文献   

12.
Using Cudrania tricuspidata cells as model plant cells which have high sensitivity to hydrodynamic stress, technological problems in the cultivation of the plant cells at high density were investigated. Using "shake" flasks on a reciprocal shaker and Erlenmeyer flasks on a rotary shaker and with a high supply of oxygen in order to obtain high cell densities in shaken cultures, particle breakdown and damage to the largest cell aggregate group (above 1981 microm in diameter) occurred and normal cell growth became impeded. The mass-transfer coefficient (K) for a model solid-liquid system (beta-naphthol particles and water) in place of a system of plant cells and a liquid medium was proposed as an intensity index of hydrodynamic stress effects on plant cells in suspension cultures under various conditions in the bioreactor systems. Normal cell growth was obtained under culture conditions for K values less than about 4.4 x 10(-3) cm/sec. The characteristics of various bioreactors used until now were investigated by considering the three main technological factors (capacity of oxygen supply, intensity of hydrodynamic stress effects on plant cells, and intensity of culture broth mixing and air-bubble dispersion). The most suitable bioreactor for culturing plant cells at high density was a jar fermentor with a modified paddle-type impeller (J-M). The yield of cell mass in the 10-liter J-M (working volume 5 liter) was about 30 g dry weight per liter of medium.  相似文献   

13.
Pseudomonas oleovorans is able to accumulate poly(3-hydroxyalkanoates) (PHAs) under conditions of excess n-alkanes, which serve as sole energy and carbon source, and limitation of an essential nutrient such as ammonium. In this study we aimed at an efficient production of these PHAs by growing P. oleovorans to high cell densities in fed-batch cultures.To examine the efficiency of our reactor system, P. oleovorans was first grown in batch cultures using n-octane as growth substrate and ammonia water for pH regulation to prevent ammonium limiting conditions. When cell growth ceased due to oxygen limiting conditions, a maximum cell density of 27 g .L(-1) dry weight was obtained. When the growth temperature was decreased from the optimal temperature of 30 degrees -18 degrees C, cell growth continued to a final cell density of 35 g . L(-1) due to a lower oxygen demand of the cells at this lower incubation temperature.To quantify mass transfer rates in our reactor system, the volumetric oxygen transfer coefficient (k(L)a) was determined during growth of P. oleovorans on n-octane. Since the stirrer speed and airflow were increased during growth of the organism, the k(L)a also increased, reaching a constant value of 0.49 s(-1) at maximum airflow and stirrer speed of 2 L . min(-1) and 2500 rpm, respectively. This k(L)a value suggests that oxygen transfer is very efficient in our stirred tank reactor.Using these conditions of high oxygen transfer rates, PHA production by P. oleovorans in fed-batch cultures was studied. The cells were first grown batchwise to a density of 6 g . L(-1), after which a nutrient feed, consisting of (NH(4))(2)SO(4) and MgSO(4), was started. The limiting nutrient ammonium was added at a constant rate of 0.23 g NH(4) (+) per hour, and when after 38 h the feed was stopped, a biomass concentration of 37.1 g . L(-1) was obtained. The Cellular PHA content was 33% (w/w), which is equal to a final PHA yield of 12.1 g . L(-1) and an overall PHA productivity of 0.25 g PHA produced per liter medium per hour. (c) 1993 John Wiley & Sons, Inc.  相似文献   

14.
Undifferentiated, highly chlorophyllous cell cultures; undifferentiated white cell cultures; green, shoot-forming cultures; and white, shoot-forming cultures of Digitalis purpurea L. were established and subcultured every 3 weeks in liquid media in the light or in the dark. The digitoxin content, the chlorophyll content, and the ribulose bisphosphate carboxylase activity of these cultures were assayed. The light-grown, green, shoot-forming cultures accumulated considerable amounts of digitoxin (about 20 to 40 micrograms per gram dry weight), and the white, shoot-forming cultures without chloroplasts accumulated about one-third that amount of digitoxin. The chlorophyll content and the ribulose bisphosphate carboxylase activity of the undifferentiated green cells were about the same as they were in the green, shoot-forming cultures, but the digitoxin content of the former was extremely low (about 0.05 to 0.2 microgram per gram dry weight), which is about the same as that in undifferentiated white cells without chloroplasts. Thus, it was concluded that the chloroplasts are not essential for the synthesis of digitoxin in Digitalis cells. The optimum concentrations of the tested compounds for accumulation of digitoxin were: benzyladenine, 0.01 to 1 milligram per liter; indoleacetic acid, 0.1 to 1 milligram per liter; α-naphthaleneacetic acid; 0.1 milligram per liter; and 2,4-dichlorophenoxyacetic acid, 0.01 milligram per liter.  相似文献   

15.
Strain GM-14 was isolated by selective enrichment from contaminated soil with chlorobenzene as the sole source of carbon and energy. It utilizes an exceptionally wide spectrum of haloaromatic substrates. It is a gram-positive, weakly acid-fast actinomycete, with a morphological cycle from cocci and short rods to long rods and branched filaments; it grew optimally at 28(deg)C; and it tolerated 5% NaCl in rich medium. The chemotaxonomic characteristics, the diagnostic biochemical tests, the whole-cell fatty acid composition, and 16S rDNA analysis were consistent with Rhodococcus opacus. R. opacus GM-14 grew on 48 of 117 different aromatic and haloaromatic compounds. It utilized phenol at concentrations up to 1.2 g/liter, 3- and 4-methylphenols up to 0.5 g/liter, 2- and 4-chlorophenols up to 0.25 g/liter, and 3-chlorophenol up to 0.1 g/liter. It grew in saturated aqueous solutions of benzene, chlorobenzene, and 1,3- and 1,4-dichlorobenzene (up to 13, 3, 0.5, and 0.5 g/liter, respectively). The specific growth rate of strain GM-14 on phenol and 3- and 4-chlorophenols in batch culture was 0.27 to 0.29 h(sup-1), and that on benzene and chlorobenzene was similar to the rate on fructose, i.e., 0.2 h(sup-1). The growth yield on benzene and on chlorobenzene (<=0.4 g liter(sup-1)) was 40 to 50 g (dry weight) per mol of substrate consumed, equalling 8 g of dry weight biomass per mol of substrate carbon, similar to that obtained on acetate. During growth of strain GM-14 on chlorobenzene, 1,3-dichlorobenzene, and all isomers of monochlorophenol, stoichiometric amounts of chloride were released, and 50% of the stoichiometric amount was released from 1,4-dichlorobenzene.  相似文献   

16.
Growth and phycocyanin production in batch and fed-batch cultures of the microalga Galdieria sulphuraria 074G, which was grown heterotrophically in darkness on glucose, fructose, sucrose, and sugar beet molasses, was investigated. In batch cultures, specific growth rates and yields of biomass dry weight on the pure sugars were 1.08-1.15 day-1 and 0.48-0.50 g g-1, respectively. They were slightly higher when molasses was the carbon source. Cellular phycocyanin contents during the exponential growth phase were 3-4 mg g-1 in dry weight. G. sulphuraria was able to tolerate concentrations of glucose and fructose of up to 166 g L-1 (0.9 M) and an ammonium sulfate concentration of 22 g L-1 (0.17 M) without negative effects on the specific growth rate. When the total concentration of dissolved substances in the growth medium exceeded 1-2 M, growth was completely inhibited. In carbon-limited fed-batch cultures, biomass dry weight concentrations of 80-120 g L-1 were obtained while phycocyanin accumulated to concentrations between 250 and 400 mg L-1. These results demonstrate that G. sulphuraria is well suited for growth in heterotrophic cultures at very high cell densities, and that such cultures produce significant amounts of phycocyanin. Furthermore, the productivity of phycocyanin in the heterotrophic fed-batch cultures of G. sulphuraria was higher than is attained in outdoor cultures of Spirulina platensis, where phycocyanin is presently obtained.  相似文献   

17.
Ginseng (Panax ginseng C.A. Meyer) hairy root cultures, which are established via the infection of ginseng root discs withRhizobium rhizogenes, have been used to construct profiles of both biomass growth and nutrient consumption in flask cultures. In a 250 mL shake flask culture, the maximum biomass was observed on the 59th day of the culture period, at 216.8 g (fresh wt) per liter or 11.4 g (dry wt) per liter. The hairy roots were determined to have a growth rate of 0.355 g-DW/g cells/day during the exponential growth phase and a maximum specific growth rate on day 7. Total ginseng saponin and phenolic compound contents were noted to have increased within the latter portion of the culture period. Linear correlations between increases in biomass weight and nutrient uptake were used to imply the conductivity yield 2.60 g-DW/(L·mS) and carbon yield 0.45 g-DW/(g sugar) in the 250 mL flask cultures. The biomass yield when two different nitrogen sources were used (ammonia and nitrate) was shown to remain approximately constant, at 0.47 g-DW/(l·mM NH4) and 0.33 g-DW/(L·mM NO3); it remained at these levels for 16 days with the ammonia, and for 24 days with the nitrate. The biomass yield when a phosphate source was used was also shown to remain approximately constant for 9 days, at 3.17 g-DW/(L·mM PO4), with an R2 of 0.99.  相似文献   

18.
Alcaligenes eutrophus was grown autotrophically in 23-liter batch cultures in a controlled H2-O2-CO2 atmosphere. It was demonstrated that the need for periodic supplements of individual nutrients could be anticipated before cell growth depleted these nutrients to the point of becoming growth rate limiting. As a result, exponential growth was extended to optical densities of 44, with doubling times maintained at 2 h. Cultures having an initial optical density of 0.040 to 0.70 reached the final optical density of 60 in about 25 h. The final viable count was 1.2 X 10(11) cells per ml, and the dry weight was 25 g/liter.  相似文献   

19.
Dense autotrophic cultures of Alcaligenes eutrophus.   总被引:8,自引:3,他引:5       下载免费PDF全文
Alcaligenes eutrophus was grown autotrophically in 23-liter batch cultures in a controlled H2-O2-CO2 atmosphere. It was demonstrated that the need for periodic supplements of individual nutrients could be anticipated before cell growth depleted these nutrients to the point of becoming growth rate limiting. As a result, exponential growth was extended to optical densities of 44, with doubling times maintained at 2 h. Cultures having an initial optical density of 0.040 to 0.70 reached the final optical density of 60 in about 25 h. The final viable count was 1.2 X 10(11) cells per ml, and the dry weight was 25 g/liter.  相似文献   

20.
The biological utilization of CO(2) and H(2) for the formation of short-chain fatty acids was studied by using a mixed culture of bacteria. Optimization of a medium was carried out in continuous culture to identify limiting factors which controlled growth and production of organic acids. The optimal pH for growth and acid production was 7.0 at 37 degrees C; the maximal cell concentration obtained was 5.9 g of cells per liter (dry weight), and the maximal amount of volatile acids formed was 4.7 g/liter, with acetic acid as the predominant acid. With the optimized medium, it was found that the rate of transfer of hydrogen or carbon dioxide, or both, from gas to liquid was the limiting factor which controlled growth and production of acids.  相似文献   

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