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1.
Optimization of submerged culture conditions for the production of mycelial growth and exopolysaccharides (EPSs) by Collybia maculata was investigated. The optimum temperature and the initial pH for EPS production in a shake-flask culture of C. maculata were found to be 20°C and 5.5, respectively. Among the various medium’s constituents examined, glucose, Martone A-1, K 2HPO 4, and CaCl 2 were the most suitable carbon, nitrogen, and mineral sources for EPS production, respectively. The optimum concentration
of the medium’s ingredients determined using the orthogonal matrix method was as follows: 30 g/L of glucose, 20 g/L of Martone
A-1, 1g/L of K 2HPO 4, and 1g/L of CaCl 2. Under the optimized culture conditions, the maximum concentration of EPSs in a 5-L stirred-tank reactor was 2.4 g/L, which
was approximately five times higher than that in the basal medium. A comparative fermentation result showed that the EPS productivity
in an airlift reactor was higher than that in the stirred-tank reactor despite the lower mycelial growth rate. The specific
productivities and the yield coefficients in the airlift reactor were higher than those in the stirred-tank reactor even though
the volumetric productivities were higher in the stirred-tank reactor than in the airlift reactor. 相似文献
2.
The economics of using Na 2CO 3 rather than CaCO 3 as the neutralizing agent in fumaric acid production by Rhizopus arrhizus is investigated and compared with the benzene route. Because sodium fumarate, unlike calcium fumarate, is soluble, downstream
processing is simplified by requiring less equipment and no heat, and also allows the reuse of cells. In spite of a fumaric
acid productivity (g/L/h) 2.4 x lower than the CaCO 3 case, the Na 2CO 3 alternative with cell reuse has a higher rate of return. However, with the current cost of petroleum, the selling price of
fumaric acid from the benzene route is half as much as from an idealized Na 2CO 3 fermentation. 相似文献
3.
In the present experiments, the monodisperse calcium carbonate nanoparticles obtained in the reactor (three-phase reaction) with rotating discs have been covered with α-cyclodextrin. Both pure CaCO3 nanoparticle and α-cyclodextrin-coated CaCO3 powders were deeply analysed by the use of the scanning electron microscope, the dynamic light scattering and the thermogravimetric method. The experimental data have allowed for determination of effective diameter of the obtained particles (aggregates of ca. 30 nm single crystals) and their size distribution (almost monodisperse—ca. 390 nm) as well as for distinction between α-cyclodextrin molecules present on calcite surface or free α-cyclodextrin molecules if presented in the sample. It was found that the nanometric CaCO3 obtained in the reactor with rotating discs can be covered with a maximum of 1.15% α-cyclodextrin monolayer. The maximal coverage of the CaCO3 calcite particles with α-cyclodextrin can be done by 24-h shaking of 50 mg nanometric calcium carbonate with 25 mg of 36.79 mM α-cyclodextrin aqueous solution.
相似文献
4.
Rotating disc reactor
(RDR) was constructed to conduct gas–liquid–solid reactions with
controlled reagent transfer from gaseous to liquid phase. The concept is based
on continuous formation of thin liquid films at a surface of rotating discs
where the mass transfer proceed in diffusion–convective way.
The reactor was employed
to run precipitation reaction of CaCO 3 via carbon dioxide
absorption in lime slurry. During each reaction pH changes and Ca 2+
concentration in time were measured. Disc rotations and gas flows were changed
during the experiment and their influence on the obtained CaCO 3
powders has been examined and fully discussed. 相似文献
5.
The global oxygen uptake rate (OUR) and specific oxygen uptake rates (SOUR) were determined for different values of the volumetric
oxygen mass transfer coefficient (15, 43, and 108 h −1), and for varying initial xylose concentrations (50, 100, 150, and 200 g/L) in shaking flasks. The initial cell concentration
was 4.0 g/L, and there was only significant growth in the fermentation with the highest oxygen availability. In this condition,
OUR increased proportionally to cell growth, reaching maximum values from 2.1 to 2.5 g of O 2/(L·h) in the stationary phase when the initial substrate concentration was raised from 50 to 200 g/L, respectively. SOUR
showed different behavior, growing to a maximum value coinciding with the beginning of the exponential growth phase, after
which point it decreased. The maximum SOUR values varied from 265 to 370 mg of O 2/(g of cell·h), indicating the interdependence of this parameter and the substrate concentration. Although the volumetric
productivity dropped slightly from 1.55 to 1.18 g of xylitol/(L·h), the strain producing capacity ( γ
P/X
) rose from 9 to 20.6 g/g when the initial substrate concentration was increased from 50 to 200 g/L. As for the xylitol yield
over xylose consumed ( γ
P/S
), there was no significant variation, resulting in a mean value of 0.76 g/g. The results are of interest in establishing
a strategy for controlling the dynamic oxygen supply to maximize volumetric productivity. 相似文献
6.
A starter culture of Trichoderma reesei (Rut-C30) prepared in a liquid fluidized bed reactor (LFBR) gave better growth and greater cellulase production in submerged
fermentation than a conventional shake flask inoculum. The LFBR starter was prepared by first coating T. reesei spores to 0.25 mm size corncob (1.0x10 8g -1) in a medium containing 1.0% corncob, 0.5 gL -1 xylose and 0.1 gL -1 lactose in a balanced salt solution, then fluidizing the particles in the LFBR for 36 h to allow germination of the spores,
and covering the particles with an approx 30 μm thick biofilm. This biofilm that developed in constant adherence to the lignocellulosic
carrier, apparently became well adapted to grow rapidly on insoluble cellulose substrates (Solca Floc), and had the enzymes
of the cellulase complex induced for increased cellulase production.
The LFBR starter used in a stirred tank reactor (STR) gave 15 gL -1 biomass production and 6.5 IU mL -1 overall cellulase activity with a volumetric productivity of 64 IU L -1h -1 in a 5 d fermentation, compared with a 7 d shake flask inoculum that gave 11 gL -1 biomass and 3.2 IU mL -1 cellulase activity, with a volumetric productivity of 31IU L -1h -1. The LFBR starter culture retained its viability in dry storage for 6–9 mo. 相似文献
7.
The production of lactic acid from glucose has been demonstrated using a CSTR (continuous stirred-tank reactor) with cell
recycle. Studies were conducted with Lactobacillus delbrueckii at a fermentation temperature of 42°C and a pH of 6.25. A cell density of 140 g dry weight/L and a volumetric productivity
of 150 g/L.h, with complete glucose consumption, were obtained. It was not possible to obtain a lactic acid concentration
above 60 g/L because of product inhibition. A cell purge was not necessary to maintain high viability bacteria culture or
to obtain a steady state. At steady state the net cell growth appeared to be negligible. The specific glucose consumption
for cell maintenance was 0.33 g glucose/g cells-h. 相似文献
8.
The influence of aeration level, initial pH, initial cell concentration, and fermentation time on the xylitol production from
rice straw hemicellulose hydrolysate by Candida mogii was studied. A multifactorial experimental design was adopted to evaluate this influence. A statistical analysis of the results
showed that the aeration level and the initial pH had significant effects on yield factor, volumetric productivity, and xylose
consumption. For the latter, fermentation time was also a significant variable. Based on the response surface methodology,
models for the range investigated were proposed. The maximum values for the yield factor (Y p/s) and volumetric productivity (Q p) were, respectively, 0.71 g/g and 0.46 g(Lh). 相似文献
9.
Three different yeasts, Pachysolen tannophilus, Debaryomyces hansenii, and Candida guilliermondii, were evaluated to ferment xylose solutions prepared from hardwood hemicellulose hydrolysates, among which P. tannophilus proved to be the most promising microorganism. However, the presence of both lignin-derived compounds (LDC) and acetic acid
rendered a poor fermentation. To enhance the fermentation kinetics, different treatments to purify the hydrolysates were studied,
including overliming, charcoal adsorption for LDC removal, and evaporation for acetic acid and furfural stripping. Under the
best operating conditions assayed, 39.5g/L of xylitol were achieved after 96 h of fermentation, which corresponds to a volumetric
productivity of 0.41 g/L·h and a yield of product on consumed substrate of 0.63 g
p
/g S. 相似文献
10.
Although most fermentation ethanol is currently produced in traditional batch processes with yeast, the ethanologenic bacterium Zymomonas mobilis is recognized as an alternative process organism for fuel alcohol production. Different strategies for improving the productivity
of ethanol fermentations are reviewed. In batch and open-type continuous fermentations the advantage of replacing yeast by Zymomonas relates principally to the 10% higher fermentation efficiency (product yield), whereas in high cell density, closed-type
continuous systems (operating with cell recycle or retention) the superior kinetic properties of Zymomonas can be exploited to affect about a five-fold improvement in volumetric productivity. Unlike yeast, the rate of energy supply
(conversion of glucose to ethanol) in Zymomonas is not strictly regulated by the energy demand and a nongrowing culture exhibits a maintenance energy coefficient that is
at least 25 times higher than yeast. As an alternative to process improvement through genetic engineering of the process organism
this investigation has taken a biochemical and physiological approach to increasing the kinetic performance of Z. mobilis through manipulation and control of the chemical environment. Energetically “uncoupled” phenotypes with markedly increased
specific rates of ethanol production were generated under conditions of nutritional limitation (nitrogen, phosphate, or potassium)
in steady-state continuous culture. The pH was shown to influence energy coupling in Zymomonas affecting the maintenance coefficient ( m
e
) rather than the max growth yield coefficient ( Y
x
sάx
). Whereas the pH for optimal growth of Z. mobilis (ATCC 29191) in a complex medium was 6.0–6.5, the specific rate of ethanol production in continuous fermentations was maximal
in the range 4.0–4.5. Fermentation conditions are specified for maximizing the specific productivity of a Zymomonas-based continuous ethanol fermentation where the potential exists for improving the volumetric productivity in dense culture
fermentations with an associated 35–40% reduction in capital costs of fermentation equipment and an estimated savings of 10–15%
on cost of product recovery (distillation), and 3–7% on overall production costs based on the projected use of inexpensive
feedstocks. 相似文献
11.
Two distinctive forms of growth (mycelial filamentous and mycelial pellets) of Rhizopus oryzae were obtained by manipulating the initial pH of the medium with the controlled addition of CaCO 3 in a bubble fermenter. In the presence of CaCO 3, diffused filamentous growth was obtained when the initial pH of the substrate was 5.5. In the absence of CaCO3, mycelial
pellet growth was obtained when the initial pH was 2.0. The fermentation study indicated that the mycelial growth has a shorter
lag period before the onset of acid formation. Both physical forms of growth of Rhizopus exhibited a high yield of L-lactic acid in the bubble fermenter when the initial glucose concentration exceeded 70 g/L. A
final lactic acid concentration of 62 g/L was produced by the filamentous form of Rhizopus from 78 g/L glucose after 27 h. This showed a weight yield of 80% of glucose consumed, with an average specific productivity
of 1.46 g/h/g. Similarly, the pellet form of Rhizopus produced a final lactic acid concentration of 66 g/L from 76 g/L glucose after 43 h, with a weight yield of 86% and an average
specific productivity of 1.53 g/h/g. 相似文献
12.
A highly efficient spray-cycle reactor for oxygen supply was developed. A typical arrangement of the reactor consists of a
spray column fitted with a nozzle and a coaxal tube, and a reservoir vessel. The culture broth was circulated between the
column and vessel by a peristaltic pump. The volumetric oxygen-transfer coefficient, k 1a was evaluated as a parameter for oxygen supply. The liquid circulation rate in the spraycycle reactor was represented in
terms of the number of circulations. The k 1a value increased as the number of circulations increased, reaching 208 h -1 at 4.4 min -1 of circulation numbers. This value was 1.8 times higher than that in a 1500-mL stirred-tank reactor under the agitation of
20.7g and the aeration of 1.0 volume per min.
The spray-cycle reactor was applied to riboflavin production by an aerobic microorganism. The riboflavin production increased
as k 1a values increased and the maximal riboflavin production was 161 mg/L at 208 h -1 of k 1a. These results suggest that the spray-cycle reactor is useful to oxygen-demanding fermentation because of the high k 1a value in comparison with the stirred-tank reactor. 相似文献
13.
The interactions between an organic polymer with plasticizing activity and a model surface (CaCO 3), with a surface activity similar to the cement one, have been analysed by volumetric analysis and thermal analysis: TG/DTG
and DSC. The synthesized polymer has a negative link site (carboxylate) that is able to interact with the substrate and a
long ethylene oxide chain that contribute to the dispersing activity. The pattern of the adsorption isotherm suggests the
occurring of a step like adsorption, initially characterised by a coil conformation of PEO chain followed by a more PEO strained,
linear, conformation as the amount of polymer increases. The polymer adsorption appears to modify the crystalline phase and
morphology of the CaCO 3 surface as the thermal analysis puts in evidence through the CaCO 3 decomposition temperature shifts. SEM analysis confirms the morphology changes induced by polymer adsorption. 相似文献
14.
The effect of carbon source and its concentration, inoculum size, yeast extract concentration, nitrogen source, pH of the
fermentation medium, and fermentation temperature on β-glucosidase production by Kluyveromyces marxianus in shake-flask culture was investigated. These were the independent variables that directly regulated the specific growth
and β-glucosidase production rate. The highest product yield, specific product yield, and productivity of β-glucosidase occurred
in the medium (pH 5.5) inoculated with 10% (v/v) inoculum of the culture. Cellobiose (20 g/L) significantly improved β-glucosidase
production measured as product yield ( Y
P/S
) and volumetric productivity ( Q
P
) followed by sucrose, lactose, and xylose. The highest levels of productivity (144 IU/[L·h]) of β-glucosidase occurred on
cellobiose in the presence of CSL at 35°C and are significantly higher than the values reported by other researchers on almost
all other organisms. The thermodynamics and kinetics of β-glucosidase production and its deactivation are also reported. The
enzyme was substantially stable at 60°C and may find application in some industrial processes. 相似文献
15.
Wheat straw hydrolysate produced by enzymatic hydrolysis of hydrothermal pretreated wheat straw at a very high solids concentration of 30% dry matter ( w/ w) was used for testing the effect of nutrients on their ability to improve fermentation performance of Saccharomyces cerevisiae. The nutrients tested were MgSO 4 and nitrogen sources; (NH 4) 2SO 4, urea, yeast extract, peptone and corn steep liquor. The fermentation was tested in a separate hydrolysis and fermentation process using a low amount of inoculum (0.33 g kg ?1) and a non-adapted baker’s yeast strain. A factorial screening design revealed that yeast extract, peptone, corn steep liquor and MgSO 4 were the most significant factors in obtaining a high fermentation rate, high ethanol yield and low glycerol formation. The highest volumetric ethanol productivity was 1.16 g kg ?1 h ?1 and with an ethanol yield close to maximum theoretical. The use of urea or (NH 4) 2SO 4 separately, together or in combination with MgSO 4 or vitamins did not improve fermentation rate and resulted in increased glycerol formation compared to the use of yeast extract. Yeast extract was the single best component in improving fermentation performance and a concentration of 3.5 g kg ?1 resulted in high ethanol yield and a volumetric productivity of 0.6 g kg ?1 h ?1. 相似文献
16.
Oxygen availability is the most important environmental parameter in the production of xylitol by yeasts, directly affecting
yields and volumetric productivity. This work evaluated the cell behavior in fermentations carried out with different dissolved
oxygen concentrations (0.5–30.0% of saturation), as well as a limited oxygen restriction (0% of saturation), at several oxygen
volumetric transfer coefficients (12 ≤ k
L
a ≤ 70 h −1). These experiments allowed us to establish the specific oxygen uptake rate limits to ensure high yields and volumetric productivity.
When oxygen availability was limited, the specific oxygen uptake rate values were between 12 and 26 mg of O 2/of g cell·h, resulting in a yield of 0.71 g of xylitol/xylose consumed, and 0.85 g/[L·h] for the volumetric productivity.
According to the results, the effective control of the specific oxygen uptake rate makes it possible to establish complete
control over this fermentative process, for both cell growth and xylitol production. 相似文献
17.
The fermentation kinetics for the conversion of rice straw hemicellulosic hydrolysate to xylitol by the yeast Candida guilliermondii was evaluated under batch conditions. The fermentation was accomplished in a 1 L working volume stirred-tank reactor with
aeration of 1.3 vvm and agitation of 300 rpm (k La=15/h). The maximum specific rate of xylitol formation (0.12 g/g) was achieved when the specific growth rate was lowered
to 1/5 of its highest value. From analysis of the fermentation kinetics, a linear correlation between specific growth rate
(μ x) and specific rate of xylitol formation (q p) was evident. Based on the Gaden model, this bioprocess was classified as growth-associated production and the relationship
between μ x and q p can be described by the equation q p=6.31μ x. 相似文献
18.
在 L-蛋氨酸( L-Met)的导向下,可控制备了一种单层中空CaCO 3微球。考察了 L-Met的加入量、CO 2流速和反应温度等重要参数对CaCO 3形貌、尺度和晶相的影响。作为一种客体分子载体,该单层中空CaCO 3微球可负载罗丹明B(RhB),得到一种发光复合材料(RhB@hollow-CaCO 3)。RhB@hollow-CaCO 3)对A-549肺癌细胞(A549 LCCs)和HO8910人卵巢癌细胞(HO8910 OCCs)表现出良好的生物相容性。 相似文献
19.
Calcium carbonate (CaCO 3) is an inorganic compound which is widely used in industry, chemistry, construction, ocean acidification, and biomineralization due to its rich constituent on earth and excellent performance, in which calcium carbonate hydrates are important systems. In Zou et al's work ( Science, 2019, 363, 396-400), they found a novel calcium carbonate hemihydrate phase, but the structural stability, optical, and mechanical properties have not been studied. In this work, the stability, electronic, optical, and mechanical properties of novel calcium carbonate hydrates were investigated by using the first-principles calculations using density functional theory. CaCO 3· xH 2O ( x = 1/2, 1 and 6) are determined dynamically stable phases by phonon spectrum, but the Gibbs energy of reaction of CaCO 3·1/2H 2O is higher than other calcium carbonate hydrates. That is why CaCO 3·1/2H 2O is hard to synthesize in the experiments. In addition, the optical and mechanical properties of CaCO 3· xH 2O ( x = 1/2, 1 and 6) are expounded in detail. It shows that the CaCO 3·1/2H 2O has the largest bulk modulus, shear modulus, and Young's modulus with the values 60.51 GPa, 36.56 GPa, and 91.28 GPa. This work will provide guidance for experiments and its applications, such as biomineralization, geology, and industrial processes. 相似文献
20.
Batch fermentations of sugar cane bagasse hemicellulosic hydrolysate treated for removing the inhibitors of the fermentation
were performed by Candida guilliermondii FTI20037 for xylitol production. The fermentative parameters agitation and aeration rate were studied aiming the maximization
of xylitol production from this agroindustrial residue. The maximal xylitol volumetric productivity (0.87 g/L h) and yield
(0.67 g/g) were attained at 400/min and 0.45 v.v.m. (K La 27/h). According to the results, a suitable control of the oxygen input permitting the xylitol formation from sugar cane
bagasse hydrolysate is required for the development of an efficient fermentation process for large-scale applications. 相似文献
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