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1.
The dynamics of ethanol production/consumption in baker's yeast were studied under feed- rate controlled conditions. The yeast was grown on molasses in an 8-l fed-batch reactor and experiments were done at cell concentrations between 5 and 65 g l?1. Small changes in the feed rate were made around a feed rate corresponding to the critical growth rate, at which the yeast cell metabolism switches between ethanol consumption and production. A membrane gas sensor was used for on-line measurement of the ethanol concentration in the broth. The measured ethanol signal was used for control and the system was excited through changes in the regulator set-point. The closed-loop experiments ensured that feed variations were within the critical range, and thus facilitated reproducible experiments. Data were fitted to a second-order difference equation by statistical methods. Results were compared with a theoretically derived model. The process gain could be understood in terms of the underlying stoichiometry by using the “bottleneck” view of yeast glucose metabolism. The process time constant was found to be longer than is implied by a simple Monod relation between glucose uptake rate and concentration. 相似文献
2.
Kinetics of Growth and Enhanced Sophorolipids Production by Candida bombicola Using a Low-Cost Fermentative Medium 总被引:1,自引:0,他引:1
In this study, effect of various parameters on sophorolipid (SL) production by the yeast Candida bombicola was investigated for the enhancing of its production by employing L18 orthogonal array design of experiments. At optimum
conditions of sugarcane molasses 50 g l−1, soybean oil 50 g l−1, inoculum size 5% (v/v), temperature 30 °C, inoculum age 2 days, and agitation 200 rpm, the yeast produced almost equal amounts of the product in
batch shake flasks and in a 3-l fermentor without any pH control (45 and 47 g l−1, respectively). However, the yield increased to 60 g l−1 in the fermentor under controlled pH environment. Time course of SL production, yeast biomass growth, and utilization of
sugarcane molasses and soybean oil at these optimized conditions were fitted to existing kinetic models reported in the literature.
Estimated kinetic parameters from these models suggested that conventional medium containing glucose can very well be replaced
with the present low-cost fermentative medium. 相似文献
3.
Optimization of Surfactin Production by <Emphasis Type="Italic">Bacillus subtilis</Emphasis> Isolate BS5 总被引:1,自引:0,他引:1
Abdel-Mawgoud AM Aboulwafa MM Hassouna NA 《Applied biochemistry and biotechnology》2008,150(3):305-325
Bacillus subtilis BS5 is a soil isolate that produces promising yield of surfactin biosurfactant in mineral salts medium (MSM). It was found that cellular growth and surfactin production in MSM were greatly affected by the environmental fermentation conditions and the medium components (carbon and nitrogen sources and minerals). Optimum environmental conditions for high surfactin production on the shake flask level were found to be a slightly acidic initial pH (6.5-6.8), an incubation temperature of 30 degrees C, a 90% volumetric aeration percentage, and an inoculum size of 2% v/v. For media components, it was found that the optimum carbon source was molasses (160 ml/l), whereas the optimum nitrogen source was NaNO(3) (5 g/l) and the optimum trace elements were ZnSO(4).7H(2)O (0.16 g/l), FeCl(3).6H(2)O (0.27 g/l), and MnSO(4).H(2)O (0.017 g/l). A modified MSM (molasses MSM), combining the optimum medium components, was formulated and resulted in threefold increase in surfactin productivity that reached 1.12 g/l. No plasmid could be detected in the tested isolate, revealing that biosurfactant production by B. subtilis isolate BS5 is chromosomally mediated but not plasmid-mediated. 相似文献
4.
Yoshiharu Yamane Yozo Nakamura Hiroyuki Okamoto Hiroshi Ooshima Jyoji Kato 《Applied biochemistry and biotechnology》1995,50(3):317-322
Effects of pH and dissolved oxygen concentration on batchwise riboflavin production by a 5-fluorouracil (5-FU)-resistant mutant
ofArthrobacter sp. were investigated. The reaction was carried out in a jar fermentor. The optimal pH of culture medium was around 7.3.
Dissolved oxygen concentration was almost constant during fermentation at 600 rpm of agitation rate. Production of riboflavin
reached a maximum of 160 mg/L after 70 h fermentation under the agitation rate of 600 rpm, aeration rate of 1.0 L/min, and
pH 7.0. 相似文献
5.
Gamma-linolenic acid (GLA, C18:3Δ6,9,12) is an n-6 polyunsaturated fatty acid (PUFA) that has been used for the alleviation and treatment of a number of symptoms and diseases.
Increasing GLA demand has led to a search for alternative producers and potential strategies for GLA production. Based on
the successful performance of Hansenula polymorpha, a methylotrophic yeast, as a “cell factory” for the production of valuable bioproducts, a bioprocess development approach
was implemented for GLA production in the recombinant yeast carrying the mutated Δ6-desaturase gene of Mucor rouxii. Using a substrate-feeding strategy under glycerol-limited conditions, the physical-chemical variables during the fed-batch
fermentation of the recombinant H. polymorpha were optimised for GLA production through response surface methodology using a Box-Behnken design. The medium composition,
including yeast extract and trace elements, and dissolved oxygen tension (DOT) were targeted. We found that DOT was the most
effective variable for enhancing GLA yield. These results also suggest that the optimum conditions for GLA production are
28 % saturation of DOT, 1 g L−1 of yeast extract and 3.6 mL L−1 of the Pichia trace metals 1 (PTM1). 相似文献
6.
Senthilkumar Sivaprakasam Moira Monika Schuler Adel Hama Katie-Marie Hughes Ian W. Marison 《Journal of Thermal Analysis and Calorimetry》2011,104(1):75-85
Control of bioprocesses requires reliable and robust on- or in-line monitoring tools providing real-time information on process
dynamics. Heat generation related to metabolic activity of living systems is currently gaining importance in bioprocess industry
due to its non-invasive and essentially instantaneous characteristics. This study deals with monitoring and control of pure
aerobic fed-batch cultures of three Crabtree-negative yeast strains, Kluyveromyces marxianus, Candida utilis and Pichia pastoris, based on in-line measured, metabolic heat flow signals. A high resolution biocalorimeter (BioRC1) was developed from a standard
bench-scale heat flow calorimeter (RC1). The BioRC1 was equipped with in-line (dielectric spectroscopy, pH probe and dissolved
oxygen probe) and at-line (exit gas analyser) sensors to characterise the growth behaviour of the yeast cells. Both metabolic
heat flow and biomass profiles exhibited similar behaviour proving the significance of employing heat flow signal as a key-parameter
for the system under investigation. A simple estimator for biomass concentration and specific growth rate was formulated based
on heat flow values. In order to evaluate the potential of calorimetry as a reliable and powerful process monitoring tool,
the robustness, reliability as well as the broad applicability of the developed estimators was assessed through comparison
with off-line measurement techniques and showed promising results for general applicability with a wide range of bioprocesses. 相似文献
7.
Melissa L. E. Gutarra Elisa D. C. Cavalcanti Leda R. Castilho Denise M. G. Freire Geraldo L. Sant’Anna Jr. 《Applied biochemistry and biotechnology》2005,121(1-3):105-116
The production of lipase by Penicillium simplicissimum in solid-state fermentation was studied using babassu cake as the basal medium. Tray-type and packed-bed bioreactors were employed. In the former, the influence of temperature; content of the medium, and medium supplementation with olive oil, sugarcane molasses, corn steep liquor, and yeast hydrolysate was studied. For all combinations of supplements, a temperature of 30°C, a moisture content of 70%, and a concentration of carbon source of 6.25% (m/m, dry basis) provided optimum conditions for lipase production. When used as single supplements olive oil and molasses also were able to provide high lipase activities (20 U/g). Using packed-bed bioreactors and molasses-supplemented medium, optimum conditions for enzyme production were air superficial velocities above 55 cm/min and temperatures below 28°C. The lower temperature optimum found for these reactors is probably related to radial heat gradient formation inside the packed bed. Maximum lipase activities obtained in these bioreactors (26.4 U/g) were 30% higher than in tray-type reactors. 相似文献
8.
The 1,3-dihydroxyacetone (DHA)-overproducing mutant of Gluconobacter oxydans was screened via UV mutagenesis to enhance the DHA production, and the DHA fermentation condition was optimized using the dissolved oxygen (DO) control strategy. The stable mutant G. oxydans ZJB11001 exhibits high DHA productivity and can tolerate high DHA concentrations. The optimal condition for DHA production by G. oxydans ZJB11001 in a 15-L fermentor required an initial medium containing 5 g/L yeast extract, 20 g/L glycerol, 0.5 g/L K(2)HPO(4), 0.1 g/L MgSO(4)·7H(2)O. The glycerol feeding rate was manually controlled to maintain the glycerol concentration at 5-10 g/L range. The culture pH was maintained at 6.0 within the first 20 h, and then adjusted to 5.0 until the end of the fermentation. The DO concentration increased from 20% to 30% after 24 h of fermentation, and then to 40% after 60 h of fermentation. The maximum DHA concentration of 209.6 ± 6.8 g/L was achieved after 72 h of fed-batch fermentation at 30 °C. 相似文献
9.
Effects of pH and Temperature on Recombinant Manganese Peroxidase Production and Stability 总被引:1,自引:0,他引:1
Jiang F Kongsaeree P Schilke K Lajoie C Kelly C 《Applied biochemistry and biotechnology》2008,146(1-3):15-27
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
10.
Hong-Wei Yen Chang-Yu Feng Jia-Lin Kang 《Applied biochemistry and biotechnology》2010,160(5):1441-1449
The logistic growth model combined with the Luedeking-Piret equation was adopted in this study to model the batch production
of CoQ10 in the cultivation of Rhodobacter sphaeroides. The simulation results indicated that CoQ10 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 CoQ10 concentration being produced. In this context, a fed-batch operation by molasses feeding was performed to increase the biomass
and subsequent CoQ10 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 CoQ10 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
11.
Nie ZK Ji XJ Huang H Du J Li ZY Qu L Zhang Q Ouyang PK 《Applied biochemistry and biotechnology》2011,163(8):946-953
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
12.
The effects of temperature, dissolved oxygen level, and diethyl phthalate (DEP) concentration on the rates of DEP biodegradation
have been investigated in shake flask and fermenter experiments, using aerobic and facultatively aerobic microorganisms. The
aerobic strain followed Monod growth kinetics, and was negatively affected by temperatures lower than 25 °C and dissolved
oxygen levels lower than 0.8 mg/L, whereas the specific DEP-degrading activity of the facultative strain was substrate inhibited
under anaerobic conditions, higher at 15°C than 25°C under aerobic conditions, and unaffected by the dissolved oxygen level.
Studies were also carried out in soil columns to identify additional factors that might be important for modeling DEP biodegradation. 相似文献
13.
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
14.
The effects of aeration within the range of 0.2-0.5 vvm on transformed and high yielding cell cultures of Linum album were investigated in a 5-L stirred tank bioreactor equipped with low shear Setric impeller. The kinetics of cell growth, substrate utilization, and production of lignans, namely, podophyllotoxin and 6-methoxypodophyllotoxin, were established. Maximum biomass of 23.2 g/L and lignan accumulation levels of 176.3 mg/L podophyllotoxin and 10.86 mg/L 6-methoxypodophyllotoxin were obtained with initial air flow rate of 0.3 vvm. Specified oxygen demand of cells was estimated to be 1.35 g O(2)/g biomass. The optimum oxygen transfer coefficient was found to be 16.7 h(-1) (,) which corresponded to aeration rate of 0.3 vvm. The effect of minimum dissolved oxygen (DO) concentration was investigated with respect to biomass and lignan production by comparing identically aerated and agitated bioreactor cultivations at dissolved oxygen concentrations of 10%, 30%, and 50%. Cell growth and podophyllotoxin accumulation were not affected significantly at these DO levels, but 6-methoxypodophyllotoxin production was enhanced when cells were cultivated at 30% DO level. The maximum volumetric productivities of 18.2 mg/L day and 3.2 mg/L day for podophyllotoxin and 6-methoxypodophyllotoxin, respectively, were obtained. These results establish the key role of oxygen on mass scale production of anticancer lignans by cell cultures of L. album. It may serve as a suitable parameter for scale-up. 相似文献
15.
Teemu Näykki Mirja Leivuori Katarina Björklöf Ritva Väisänen Marko Laine Tero Väisänen Ivo Leito 《Accreditation and quality assurance》2014,19(4):259-268
In 2013, Proftest SYKE organised the first proficiency test (PT) in Finland for field measurements of temperature, conductivity, dissolved oxygen concentration, oxygen saturation and pH value in river water. The aim was to pilot the organisation of an in situ proficiency test—particularly, how to select the test location—and how to assess the homogeneity and stability of the measurement site and the water to be tested. The focus was also to evaluate the suitability of the common field sensors used for water analysis, as well as the comparability of the results between the instruments under field conditions. The overall application of quality assurance procedures was also surveyed. This paper deals with the results, findings and recommendations for the measurement of pH, conductivity and dissolved oxygen concentration. In total, nine participants with 16 sensors took part in the proficiency test. For the evaluation of the performance of each participant, z scores were calculated allowing 3 % to 8 % deviation from the assigned value. The standard deviation of the participant’s results was lower than organiser expected, and 80 % of the results for pH, 79 % for conductivity and 69 % for dissolved oxygen concentration were regarded as satisfactory. According to the results, the most challenging measurement was for dissolved oxygen with a Clark cell-type measurement principle based on electrochemical reaction. All sensors tested in the PT were less than 5 years, old and they were calibrated according to the manufacturer’s instructions. None of the participants had estimated measurement uncertainty for their sensor measurements. In addition, internal and external quality assurance protocols were usually lacking. 相似文献
16.
Nuttawut Kongklom Zhongping Shi Yusuf Chisti Sarote Sirisansaneeyakul 《Applied biochemistry and biotechnology》2017,182(3):990-999
Bacillus licheniformis TISTR 1010 was used for glutamic acid-independent production of poly-γ-glutamic acid (γ-PGA). A fed-batch production strategy was developed involving feedings of glucose, citric acid, and ammonium chloride at specified stages of the fermentation. With the dissolved oxygen concentration controlled at ≥50% of air saturation and the pH controlled at ~7.4, the fed-batch operation at 37 °C afforded a peak γ-PGA concentration of 39.9 ± 0.3 g L?1 with a productivity of 0.926 ± 0.006 g L?1 h?1. The observed productivity was nearly threefold greater than previously reported for glutamic acid-independent production using the strain TISTR 1010. The molecular weight of γ-PGA was in the approximate range of 60 to 135 kDa. 相似文献
17.
A MoO3-TiO2 nanocrystalline composite material was prepared by a simple solgel method.The synthesized material was charac-terized by X-ray diffraction,scanning electron microscopy with an electron dispersion spectroscopy,transmission electron microscopy,and Fourier transform infrared spectroscopy.Melanoidin is a dark brown pigment found in wastewater from the sugar industry and it pollutes water.This polluted water is generally referred to as molasses and it undergoes fermentation and is solely responsible for water,soil,and air pollution.The synthesized catalytic material was found to be effective in degrading molasses under UV-visible radiation.Analysis of treated and untreated molasses was carried out by measuring its color,chemical oxygen demand,biological oxygen demand,pH,and total dissolved solid.Results from these analyses indicate the effective photodegradation of the molasses.This methodology has several advantages such as high photocatalytic activity,non-toxicity,cleanliness,and reusability of the catalytic material. 相似文献
18.
Madhukar NAVGIRE Ajeet YELWANDE Deepak TAYDE Balasaheb ARBAD Machhindra LANDE 《催化学报》2012,(2):261-266
A MoO3-TiO2 nanocrystalline composite material was prepared by a simple solgel method.The synthesized material was charac-terized by X-ray diffraction,scanning electron microscopy with an electron dispersion spectroscopy,transmission electron microscopy,and Fourier transform infrared spectroscopy.Melanoidin is a dark brown pigment found in wastewater from the sugar industry and it pollutes water.This polluted water is generally referred to as molasses and it undergoes fermentation and is solely responsible for water,soil,and air pollution.The synthesized catalytic material was found to be effective in degrading molasses under UV-visible radiation.Analysis of treated and untreated molasses was carried out by measuring its color,chemical oxygen demand,biological oxygen demand,pH,and total dissolved solid.Results from these analyses indicate the effective photodegradation of the molasses.This methodology has several advantages such as high photocatalytic activity,non-toxicity,cleanliness,and reusability of the catalytic material. 相似文献
19.
Pryor SW Gibson DM Hay AG Gossett JM Walker LP 《Applied biochemistry and biotechnology》2007,143(1):63-79
Bacillus subtilis strain TrigoCor 1448 was grown on wheat middlings in 0.5-l solid-state fermentation (SSF) bioreactors for the production
of an antifungal biological control agent. Total antifungal activity was quantified using a 96-well microplate bioassay against
the plant pathogen Fusarium oxysporum f. sp. melonis. The experimental design for process optimization consisted of a 26−1 fractional factorial design followed by a central composite face-centered design. Initial SSF parameters included in the
optimization were aeration, fermentation length, pH buffering, peptone addition, nitrate addition, and incubator temperature.
Central composite face-centered design parameters included incubator temperature, aeration rate, and initial moisture content
(MC). Optimized fermentation conditions were determined with response surface models fitted for both spore concentration and
activity of biological control product extracts. Models showed that activity measurements and spore production were most sensitive
to substrate MC with highest levels of each response variable occurring at maximum moisture levels. Whereas maximum antifungal
activity was seen in a limited area of the design space, spore production was fairly robust with near maximum levels occurring
over a wider range of fermentation conditions. Optimization resulted in a 55% increase in inhibition and a 40% increase in
spore production over nonoptimized conditions. 相似文献
20.
In submerged culture of Ganoderma lucidum, the pH optimum for cell growth has been shown to be lower than that for exopolysaccharides (EPS) formation. Therefore, in
the present study, a two-stage pH-control strategy was employed to maximize the productions of mycelial biomass and EPS. When
compared, a batch culture without pH control had a maximum concentration of EPS and endopolysaccharides, which was much lower
than those with pH control. Maximum mycelial growth (12.5 g/L) and EPS production (4.7 g/L) were achieved by shifting the
controlled pH from 3.0 to 6.0 after day 4. The contrast between the controlled-pH process and uncontrolled pH was marked.
By using various two-stage culture processes, it was also observed that culture pH has a significant affect on the yield of
product, mycelial morphology, chemical composition, and molecular weight of EPS. A detailed observation of mycelial morphology
revealed that the productive morphological form for EPS production was a dispersed pellet (controlled pH shifting from 3.0
to 6.0) rather than a compact pellet with a dense core area (controlled pH 4.5) or a feather-like pellet (controlled pH shifting
from 6.0 to 3.0). Three different polysaccharides were obtained from each pH conditions, and their molecular weights and chemical
compositions were significantly different. 相似文献