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1.
Prebiotic oligosaccharides are nondigestible carbohydrates that can be obtained by enzymatic synthesis. Glucosyltransferases can be used to produce these carbohydrates through an acceptor reaction synthesis. When maltose is the acceptor a trisaccharide composed of one maltose unit and one glucose unit linked by an alpha-1,6-glycosidic bond (panose) is obtained as the primer product of the dextransucrase acceptor reaction. In this work, panose enzymatic synthesis was evaluated by a central composite experimental design in which maltose and sucrose concentration were varied in a wide range of maltose/sucrose ratios in a batch reactor system. A partially purified enzyme was used in order to reduce the process costs, because enzyme purification is one of the most expensive steps in enzymatic synthesis. Even using high maltose/sucrose ratios, dextran and higher-oligosaccharide formation were not avoided. The results showed that intermediate concentrations of sucrose and high maltose concentration resulted in high panose productivity with low dextran and higher-oligosaccharide productivity. 相似文献
2.
Scheffersomyces stipitis was cultivated in an optimized, controlled fed-batch fermentation for production of ethanol from glucose–xylose mixture. Effect of feed medium composition was investigated on sugar utilization and ethanol production. Studying influence of specific cell growth rate on ethanol fermentation performance showed the carbon flow towards ethanol synthesis decreased with increasing cell growth rate. The optimum specific growth rate to achieve efficient ethanol production performance from a glucose-xylose mixture existed at 0.1 h ?1. With these optimized feed medium and cell growth rate, a kinetic model has been utilized to avoid overflow metabolism as well as to ensure a balanced feeding of nutrient substrate in fed-batch system. Fed-batch culture with feeding profile designed based on the model resulted in high titer, yield, and productivity of ethanol compared with batch cultures. The maximal ethanol concentration was 40.7 g/L. The yield and productivity of ethanol production in the optimized fed-batch culture was 1.3 and 2 times higher than those in batch culture. Thus, higher efficiency ethanol production was achieved in this study through fed-batch process optimization. This strategy may contribute to an improvement of ethanol fermentation from lignocellulosic biomass by S. stipitis on the industrial scale. 相似文献
3.
Clostridium beijerinckii BA101 (mutant strain) and C. beijerinckii 8052 (wild type) were compared for substrate and butanol inhibition. The wild-type strain is more strongly inhibited by added
butanol than is the mutant strain. Acetone and butanol were removed from a fed-batch reactor inoculated with C. beijcrinckii BA101 by pervaporation using a silicone membrane. In the batch reactor, C. beijerinckii BA101 produced 25.3 g/L of total solvents, whereas in the fermentation-recovery experiment it produced 165.1 g/L of total
solvents. Solvent productivity increased from 0.35 (batch reactor) to 0.98 g/L·h (fed-batch reactor). The fed-batch reactor
wasfed with 500 g/L of glucose-based P2 medium. Acetone selectivities ranged from 2 to 10 whereas butanol selectivities ranged
from 7 to 19. Total flux varied from 26 to 31 g/m 2·h. 相似文献
4.
Yarrowia lipolytica LgX64.81 is a non-genetically modified mutant that was previously identified as a promising microorganism for extracellular
lipase production. In this work, the development of a fed-batch process for the production of this enzyme in this strain was
described. A lipolytic activity of 2,145 U/mL was obtained after 32 h of batch culture in a defined medium supplemented with
10 g/L of tryptone, an enhancer of lipase expression. To maximize the volumetric productivity, two different fed-batch strategies
had been investigated. In comparison to batch process, the intermittent fed-batch strategy had not improved the volumetric
lipase productivity. In contrast, the stepwise feeding strategy combined with uncoupled cell growth and lipase production
phases resulted in a 2-fold increase in the volumetric lipase productivity, namely, the lipase activity reached 10,000 U/mL
after 80 h of culture. Furthermore, this lipase was purified to homogeneity by anion exchange chromatography on MonoQ resin
followed by gel filtration on Sephacryl S-100. This process resulted in an overall yield of 72% and a 3.5-fold increase of
the specific lipase activity. The developed process offers a great potential for an economic production of Lip2 at large scale
in Y. lipolytica LgX64.81. 相似文献
5.
The enzyme manganese peroxidase (MnP) is produced by numerous white-rot fungi to overcome biomass recalcitrance caused by
lignin. MnP acts directly on lignin and increases access of the woody structure to synergistic wood-degrading enzymes such
as cellulases and xylanases. Recombinant MnP (rMnP) can be produced in the yeast Pichia pastoris αMnP1-1 in fed-batch fermentations. The effects of pH and temperature on recombinant manganese peroxidase (rMnP) production
by P. pastoris αMnP1-1 were investigated in shake flask and fed-batch fermentations. The optimum pH and temperature for a standardized fed-batch
fermentation process for rMnP production in P. pastoris αMnP1-1 were determined to be pH 6 and 30 °C, respectively. P. pastoris αMnP1-1 constitutively expresses the manganese peroxidase ( mnp1) complementary DNA from Phanerochaete chrysosporium, and the rMnP has similar kinetic characteristics and pH activity and stability ranges as the wild-type MnP (wtMnP). Cultivation
of P. chrysosporium mycelia in stationary flasks for production of heme peroxidases is commonly conducted at low pH (pH 4.2). However, shake
flask and fed-batch fermentation experiments with P. pastoris αMnP1-1 demonstrated that rMnP production is highest at pH 6, with rMnP concentrations in the medium declining rapidly at
pH less than 5.5, although cell growth rates were similar from pH 4–7. Investigations of the cause of low rMnP production
at low pH were consistent with the hypothesis that intracellular proteases are released from dead and lysed yeast cells during
the fermentation that are active against rMnP at pH less than 5.5. 相似文献
6.
In fermentative hydrogen production, the low-hydrogen-producing bacteria retention rate limits the suspended growth reactor
productivity because of the long hydraulic retention time (HRT) required to maintain adequate bacteria population. Traditional
bacteria immobilization methods such as calcium alginate entrapment have many application limitations in hydrogen fermentation,
including limited duration time, bacteria leakage, cost, and so on. The use of chloroform-treated anaerobic granular sludge
as immobilized hydrogen-producing bacteria in an immobilized hydrogen culture may be able to overcome the limitations of traditional
immobilization methods. This paper reports the findings on the performance of fed-batch cultures and continuous cultures inoculated
with chloroform-treated granules. The chloroform-treated granules were able to be reused over four fed-batch cultures, with
pH adjustment. The upflow reactor packed with chloroform-treated granules was studied, and the HRT of the upflow reactor was
found to be as low as 4 h without any decrease in hydrogen production yield. Initial pH and glucose concentration of the culture
medium significantly influenced the performance of the reactor. The optimum initial pH of the culture medium was neutral,
and the optimum glucose concentration of the culture medium was below 20 g chemical oxygen demand/L at HRT 4 h. This study
also investigated the possibility of integrating immobilized hydrogen fermentation using chloroform-treated granules with
immobilized methane production using untreated granular sludge. The results showed that the integrated batch cultures produced
1.01 mol hydrogen and 2 mol methane per mol glucose. Treating the methanogenic granules with chloroform and then using the
treated granules as immobilized hydrogen-producing sludge demonstrated advantages over other immobilization methods because
the treated granules provide hydrogen-producing bacteria with a protective niche, a long duration of an active culture, and
excellent settling velocity. This integrated two-stage design for immobilized hydrogen fermentation and methane production
offers a promising approach for modifying current anaerobic wastewater treatment processes to harvest hydrogen from the existing
systems. 相似文献
7.
Lipases (triacylglycerolacyl hydrolases, EC3.1.1.3) are class of enzymes which catalyze the hydrolysis of long-chain triglycerides.
In this review paper, an overview regarding the fungal lipase production, purification, and application is discussed. The
review describes various industrial applications of lipase in pulp and paper, food, detergent, and textile industries. Some
important lipase-producing fungal genera include Aspergillus, Penicillium, Rhizopus, Candida, etc. Current fermentation process techniques such as batch, fed-batch, and continuous mode of lipase production in submerged
and solid-state fermentations are discussed in details. The purification of lipase by hydrophobic interaction chromatography
is also discussed. The development of mathematical models applied to lipase production is discussed with special emphasis
on lipase engineering. 相似文献
8.
Immobilized cell utilization in tower-type bioreactor is one of the main alternatives being studied to improve the industrial bioprocess. Other alternatives for the production of β-lactam antibiotics, such as a cephalosporin C fed-batch process in an aerated stirred-tank bioreactor with free cells of Cephalosporium acremonium, or a tower-type bioreactor with immobilized cells of this fungus, have proven to be more efficient than the batch process. In the fed-batch process, it is possible to minimize the catabolite repression exerted by the rapidly utilization of carbon sources (such as glucose) in the synthesis of antibiotics by utilizing a suitable flow rate of supplementary medium. In this study, several runs for cephalosporin C production, each lasting 200 h, were conducted in a fed-batch tower-type bioreactor using different hydrolyzed sucrose concentrations. For this study's model, modifications were introduced to take intoaccount the influence of supplementary medium flow rate. The balance equations considered the effect of oxygen limitation inside the bioparticles. In the Monod-type rate equations, cell concentrations, substrate concentrations, and dissolved oxygen were included as reactants affecting the bioreaction rate. The set of differential equations was solved by the numerical method, and the values of the parameters were estimated by the classic nonlinear regression method following Marquardt's procedure with a 95% confidence interval. The simulation results showed that the proposed model fit well with the experimental data, and based on the experimental data and the mathematical model, an optimal mass flow rate to maximize the bioprocess productivity could be proposed. 相似文献
9.
Substrate concentration in 2,3-butanediol (2,3-BD) fermentation could not be controlled well in traditional feeding strategies,
such as constant, impulse, and exponential feeding strategies. In the present study, fermentative 2,3-BD production by Klebsiella oxytoca was investigated under different batch and fed-batch strategies. The glucose-feedback fed-batch strategy was proved to be
not effective for economical 2,3-BD production for the inability of timely feeding, leading that the bacteria reused 2,3-BD
as carbon source for cell growth. Based on the phenomena that the byproducing acids caused the pH declining and the requirement
of maintaining the pH at a proper level for both cell growth and 2,3-BD accumulation, an improved strategy of pH-stat fed-batch
culture with glucose and sodium hydrate fed at the same time was established. Thus, the residual glucose concentration could
be controlled through the adjustment of pH automatically. At last, efficient 2,3-BD production was fulfilled under this fed-batch
strategy, and the highest 2,3-BD concentration, productivity, and yield were 127.9 g/l, 1.78 g/(l•h), and 0.48 g/g (2,3-BD/glucose),
respectively, compared to 98.5 g/l, 1.37 g/(l•h), and 0.43 g/g obtained in glucose-feedback fed-batch strategy. This feeding
strategy was simple and easy to operate and could be feasible for industrial 2,3-BD production in the future. 相似文献
10.
The presence of high strength fats and oils in dairy industry wastewaters poses serious challenges for biological treatment
systems, and, therefore, its pretreatment is necessary in order to remove them. In the present study, synthetic dairy wastewater
prepared in the laboratory was pretreated using the sophorolipid-producing yeast Candida bombicola in a laboratory-scale bioreactor under batch, fed-batch, and continuous modes of operation. To support the yeast growth,
the wastewater was supplemented with sugarcane molasses (1% w/ v) and yeast extract (0.1% w/ v). Results from the batch operated fermentor revealed complete utilization of fats present in the wastewater within 96 h with
more than 93% COD removal efficiency. The yeast was, however, able to pretreat the wastewater more quickly and efficiently
under fed-batch mode of operation than under batch operated condition in the same fermentor. Continuous experiments were carried
out with a wastewater retention time of 28 h in the reactor; results showed very good performance of the system in complete
utilization of fats and COD removal efficiency of more than 90%. The study proved the excellent potential of the biosurfactant-producing
yeast in pretreating high-fat- and oil-containing dairy industry wastewater. 相似文献
11.
Steam explosion pretreatment of potato for the efficient production of alcohol was experimentally studied. The amount of water-soluble
starch increased with the increase of steam pressure, but the amounts of methanol-soluble material and Klason lignin remained
insignificant, regardless of steam pressure. The potatoes exploded at high pressure were hydrolyzed into a low molecular liquid
starch, and then easily converted into ethanol by simultaneous saccharification and fermentation using mixed microorganisms:
an amylolytic microorganism, Aspergillus awamori, and a fermentation microorganism, Saccharomyces cerevisiae. The maximal ethanol concentration was 4.2 g/L in a batch culture at 15 g/L starch concentration, and 3.6 g/L in a continuous
culture fed the same starch concentration. In the fed-batch culture, the maximal ethanol concentration increased more than
twofold, compared to the batch culture. 相似文献
12.
An investigation was performed regarding the application of a mechanically stirred anaerobic sequencing batch biofilm reactor containing immobilized biomass on inert polyurethane foam (AnSBBR) to the treatment of soluble metalworking fluids to remove organic matter and produce methane. The effect of increasing organic matter and reactor fill time, as well as shock load, on reactor stability and efficiency have been analyzed. The 5-L AnSBBR was operated at 30?°C in 8-h cycles, agitation of 400 rpm, and treated 2.0 L effluent per cycle. Organic matter was increased by increasing the influent concentration (500, 1,000, 2,000, and 3,000 mg chemical oxygen demand (COD)/L). Fill times investigated were in the batch mode (fill time 10 min) and fed-batch followed by batch (fill time 4 h). In the batch mode, organic matter removal efficiencies were 87%, 86%, and 80% for influent concentrations of 500, 1,000, and 2,000 mgCOD/L (1.50, 3.12, and 6.08 gCOD/L.d), respectively. At 3,000 mgCOD/L (9.38 gCOD/L.d), operational stability could not be achieved. The reactor managed to maintain stability when a shock load twice as high the feed concentration was applied, evidencing the robustness of the reactor to potential concentration variations in the wastewater being treated. Increasing the fill time to 4 h did not improve removal efficiency, which was 72% for 2,000 mgCOD/L. Thus, gradual feeding did not improve organic matter removal. The concentration of methane formed at 6.08 gCOD/L was 5.20 mmolCH 4, which corresponded to 78% of the biogas composition. The behavior of the reactor during batch and fed-batch feeding could be explained by a kinetic model that considers organic matter consumption, production, and consumption of total volatile acids and methane production. 相似文献
13.
While many kinetic models have been developed for the enzymatic hydrolysis of cellulose, few have been extensively applied
for process design, optimization, or control. High-solids operation of the enzymatic hydrolysis of lignocellulose is motivated
by both its operation decreasing capital costs and increasing product concentration and hence separation costs. This work
utilizes both insights obtained from experimental work and kinetic modeling to develop an optimization strategy for cellulose
saccharification at insoluble solids levels greater than 15% ( w/ w), where mixing in stirred tank reactors (STRs) becomes problematic. A previously developed model for batch enzymatic hydrolysis
of cellulose was modified to consider the effects of feeding in the context of fed-batch operation. By solving the set of
model differential equations, a feeding profile was developed to maintain the insoluble solids concentration at a constant
or manageable level throughout the course of the reaction. Using this approach, a stream of relatively concentrated solids
(and cellulase enzymes) can be used to increase the final sugar concentration within the reactor without requiring the high
initial levels of insoluble solids that would be required if the operation were performed in batch mode. Experimental application
in bench-scale STRs using a feed stream of dilute acid-pretreated corn stover solids and cellulase enzymes resulted in similar
cellulose conversion profiles to those achieved in batch shake-flask reactors where temperature control issues are mitigated.
Final cellulose conversions reached approximately 80% of theoretical for fed-batch STRs fed to reach a cumulative solids level
of 25% ( w/ w) initial insoluble solids. 相似文献
14.
The logistic growth model combined with the Luedeking-Piret equation was adopted in this study to model the batch production
of CoQ 10 in the cultivation of Rhodobacter sphaeroides. The simulation results indicated that CoQ 10 production was a primary metabolite. As being a primary metabolite, a longer cell growing stage would tend to accumulate
more biomass and lead to a higher CoQ 10 concentration being produced. In this context, a fed-batch operation by molasses feeding was performed to increase the biomass
and subsequent CoQ 10 production. Three different molasses feeding strategies were operated in this study. Results suggested that the fed-batch
operation with molasses controlled at 10 ± 1 g/l could increase the cell mass and CoQ 10 concentration to reach their maximum values of 18.6 g/l and 83.8 mg/l, respectively, nearly 2.2 times and 1.9 times their
respective values obtained in the batch cultivation. 相似文献
15.
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
16.
An operable batch model of simultaneous saccharification and fermentation (SSF) for ethanol production from cellulose has been developed. The model includes four ordinary differential equations that describe the changes of cellobiose, glucose, yeast, and ethanol concentrations with respect to time. These equations were used to simulate the experimental data of the four main components in the SSF process of ethanol production from microcrystalline cellulose (Avicel PH101). The model parameters at 95% confidence intervals were determined by a MATLAB program based on the batch experimental data of the SSF. Both experimental data and model simulations showed that the cell growth was the rate-controlling step at the initial period in a series of reactions of cellulose to ethanol, and later, the conversion of cellulose to cellobiose controlled the process. The batch model was extended to the continuous and fed-batch operating models. For the continuous operation in the SSF, the ethanol productivities increased with increasing dilution rate, until a maximum value was attained, and rapidly decreased as the dilution rate approached the washout point. The model also predicted a relatively high ethanol mass for the fed-batch operation than the batch operation. 相似文献
17.
The endoglucanase I (EGI) from fungus Trichoderma reesei was cloned, expressed, and secreted from Yarrowia lipolytica using the XPR2 promoter. The signal sequence of EGI transferred from T. reesei was efficiently processed in the Y. lipolytica secretory pathway and directed the secretion of active EGI into the culture medium. However, the recombinant EGI produced
from YLCSIn strain was hyperglycosylated and significantly larger than the native enzyme produced by the parent strain. The
expression of EGI using XPR2 preproregion has caused secretion of modified proteins that still retained cellulase activity. This resulted from imprecise
processing of the N-terminus of recombinant protein. While the batch culture produced 5 mg EGI/L from YLCSIn strain, the EGI
yield was increased approx 20-fold when the fed-batch fermentation process strategy in combination with the high-cell density
cultivation technique was employed. These results showed that the Y. lipolytica is a useful host organism for production of a large amount of large size heterologous proteins, especially when used in combination
with high-cell density and fed-batch culture techniques. 相似文献
18.
Many lab-scale studies have been carried out regarding the effect of feed strategy on the performance of anaerobic sequencing
batch reactors (ASBR); however, more detailed pilot-scale studies should be performed to assess the real applicability of
this type of operation. Therefore, the objective of this work was to assess the effect of feed strategy or fill time in a
1-m 3 mechanically stirred pilot-scale sequencing batch reactor, treating 0.65 m 3 sanitary wastewater in 8-h cycles at ambient temperature. Two reactor configurations were used: one containing granular biomass
(denominated ASBR) and the other immobilized biomass on polyurethane foam as inert support (denominated anaerobic sequencing
batch biofilm reactor (AnSBBR)). The reactors were operated under five distinct feed strategies, namely: typical batch and
fed-batch for 25%, 50%, 75%, and 100% of the cycle length. Stirring frequency in the ASBR was 40 rpm with two flat-blade turbine
impellers and 80 rpm in the AnSBBR with two helix impellers. The results showed that both the ASBR and AnSBBR when operated
under typical batch, fed-batch for 50% and 75% of the cycle length, presented improved organic matter removal efficiencies,
without significant differences in performance, thus showing important operational flexibility. In addition, the reactors
presented operation stability under all conditions. 相似文献
19.
A fermentation strategy, based on the controlled feeding of growthlimiting nutrients in order to maintain metabolic activity
for extended periods, has been examined in the case of the production of a hybrid antibiotic by a transformed strain of Streptomyces lividans TK21. The fed-batch operation did not improve the results obtained with batch operation. Continuous cultures on defined medium
showed stable levels of biomass concentration, but antibiotic production ceased when continuous operation was started. The
results obtained indicate the critical influence that morphology of the cell aggregates has on metabolic activity. The antibiotic
is produced only in culture conditions providing growth in compact mycelial pellets. 相似文献
20.
During the fermentative production of 1, 3-propanediol (1,3-PD), the multiple product inhibitions cannot be negligible to accurately describe the kinetics of fermentation process. A kinetic model for fermentative production of 1,3-PD by Klebsiella pneumoniae HR526 with glycerol as carbon source under aerobic condition was proposed. The inhibitions of multiple products including 1,3-PD, 2, 3-butanediol (2,3-BD), acetate, and succinate were considered in the model. It was found that 1,3-PD, 2,3-BD, and acetate showed strong inhibitions to cell growth depending on their concentrations. The kinetic model was relatively accurate to predict the experimental data of batch, fed-batch, and continuous fermentations. The model thus can serve as a tool for further controlling and optimizing the fermentation process. 相似文献
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