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A Simple Substrate Feeding Strategy using a pH Control Trigger in Fed-Batch Fermentation 总被引:1,自引:0,他引:1
Tiong-Ee Ting Gregory J. Thoma Robert R. BeitleJr. Ralph K. Davis Rugkiat Perkins Khursheed Karim Hui-Min Liu 《Applied biochemistry and biotechnology》2008,149(1):89-98
A simple automated glucose feeding strategy based on pH control was developed to produce high-cell-density fed-batch fermentation.
In this strategy, the pH control scheme utilized an acidified concentrated glucose solution to lower the pH. The frequency
of glucose addition to the fermentor is determined by the culture’s growth kinetics. To demonstrate the effectiveness of the
coupled pH and glucose control strategy in biomass and/or secondary metabolite production, several fed-batch fermentations
of indigenous Escherichia coli and recombinant E. coli were carried out. Both strains produced biomass with optical density of greater than 40 at 600 nm. We also tested the glucose
control strategy using two types of pH controller: a less sophisticated portable pH controller and a more sophisticated online
proportional-integral-derivative (PID) controller. Our control strategy was successfully applied with both controllers, although
better control was observed using the PID controller. We have successfully demonstrated that a glucose feeding strategy based
on a simple pH control scheme to indirectly control the glucose concentration can be easily achieved and adapted to conventional
bioreactors in the absence of online glucose measurement and control. 相似文献
4.
Kim In S. Barrow Kevin D. Rogers Peter L. 《Applied biochemistry and biotechnology》2000,84(1-9):357-370
The fermentation characteristics and effects of lignocelulosic toxic compounds on recombinant Zymomonas mobilis ZM4(pZB5), which is capable of converting both glucose and xylose to ethanol, and its parental strain, ZM4, were characterized
using 13C and 31P nuclear magnetic resonance (NMR) in vivo. From the 31P NMR data, the levels of nucleoside triphosphates (NTP) of ZM(pZB5) using xylose were lower than those of glucose. This can
be related to the intrinsically slower assimilation and/or metabolism of xylose compared to glucose and is evidence of a less
energized state of ZM4(pZB5) cells during xylose fermentation. Acetic acid was shown to be strongly inhibitory to ZM4(pZB5)
on xylose medium, with xylose utilization being completely inhibited at pH 5.0 or lower in the presence of 10.9 g/L of sodium
acetate. From the 31P NMR results, the addition of sodium acetate caused decreased NTP and sugar phosphates, together with acidification of the
cytoplasm. Intracellular deenergization and acidification appear to be the major mechanisms by which acetic acid exerts its
toxic effects on this recombinant strain. 相似文献
5.
Biosilicification takes place at or very close pH 7.0 and under ambient conditions of temperature and pressure in vivo. The silicic acid transporters and the proteins facilitating biosilicification in diatoms have been identified. Silica synthesis under mild conditions in vitro has been demonstrated using synthetic polymers with control over the resulting silica morphology. The results presented herein show that the silica synthesis in vitro is not specific to particular enzymes/polypeptides due to their particular chemical structure and activity but that many other synthetic macromolecules are also capable of facilitating silica formation at neutral pH. We also report the synthesis of organic-inorganic hybrid materials that have potential in optoelectronic applications. 相似文献
6.
The economics of large-scale production of fuel ethanol from biomass and wastes requires the efficient utilization of all
the sugars derived from the hydrolysis of the heteropolymeric hemicellulose component of lignocellulosic feedstocks. Glucuronic
and 4-0-methyl-glucuronic acids are major side chains in xylans of the grasses and hardwoods that have been targeted as potential
feedstocks for the production of cellulosic ethanol. The amount of these acids is similar to that of arabinose, which is now
being viewed as another potential substrate in the production of biomass-derived ethanol.
This study compared the end-product distribution associated with the fermentation of D-glucose (Glc) and D-glucuronic acid
(GlcUA) (as sole carbon and energy sources) byEscherichia coli B (ATCC 11303) and two different ethanologenic recombinants—a strain in whichpet expression was via a multicopy plasmid (pLOI297) and a chromosomally integrated construct, strain KO11. pH-stat batch fermentations
were conducted using a modified LB medium with 2% (w/v) Glc or GlcUA with the set-point for pH control at either 6.3 or 7.0.
The nontransformed host culture produced only lactic acid from glucose, but fermentation of GlcUA yielded a mixture of ethanol,
acetic, and lactic acids, with acetic acid being the predominant end-product. The ethanol yield associated with GlcUA fermentation
by both recombinants was similar, but acetic acid was a significant by-product. Increasing the pH from 6.3 to 7.0 increased
the rate of glucuronate fermentation, but it also decreased the ethanol mass yield from 0.22 to 0.19 g/g primarily because
of an increase in acetic acid production. In all fermentations there was good closure of the carbon mass balance, the exception
being the recombinant bearing plasmid pLOI297 that produced an unidentified product from GlcUA. The metabolism of GlcUA by
this metabolically engineered construct remains unresolved. The results offered insights into metabolic fluxes and the regulation
of pyruvate catabolism in the wild-type and engineered strains. End-product distribution for metabolism of glucuronic acid
by the nontransformed, wild-typeE. coli B and recombinant strain KO11 suggests that the enzyme pyruvate-formate lyase is not solely responsible for the production
of acetylCoA from pyruvate and that derepressed pyruvate dehydrogenase may play a significant role in the metabolism of GlcUA. 相似文献
7.
This study documents the similar pH-dependent shift in pyruvate metabolism exhibited byZymomonas mobilis ATCC 29191 and ATCC 39676 in response to controlled changes in their steady-state growth environment. The usual high degree
of ethanol selectivity associated with glucose fermentation by Z.mobilis is associated with conditions that promote rapid and robust growth, with about 95% of the substrate (5% w/v glucose) being
converted to ethanol and CO2, and the remaining 5% being used for the synthesis of cell mass. Conditions that promote energetic uncoupling cause the conversion
efficiency to increase to 98% as a result of the reduction in growth yield (cell mass production). Under conditions of glucose-limited
growth in a chemostat, with the pH controlled at 6.0, the conversion efficiency was observed to decrease from 95% at a specific
growth rate of 0.2/h to only 80% at 0.042/h. The decrease in ethanol yield was solely attributable to the pH-dependent shift
in pyruvate metabolism, resulting in the production of lactic acid as a fermentation byproduct. At a dilution rate (D) of
0.042/h, decreasing from pH 6.0 to 5.5 resulted in a decrease in lactic acid from 10.8 to 7.5 g/L. Lactic acid synthesis depended
on the presence of yeast extract (YE) or tryptone in the 5% (w/v) glucose-mineral salts medium. At D = 0.15/h, reduction in
the level of YE from 3 to 1 g/L caused a threefold decrease in the steady-state concentration of lactic acid at pH 6. No lactic
acid was produced with the same mineral salts medium, with ammonium chloride as the sole source of assimilable nitrogen. With
the defined salts medium, the conversion efficiency was 98% of theoretical maximum. When chemostat cultures were used as seed
for pH-stat batch fermentations, the amount of lactic acid produced correlated well with the activity of the chemostat culture;
however, the mechanism of this prolonged induction 相似文献
8.
Lactic acid production from cellulosic biomass by cellulase andLactobacillus delbrueckii was studied in a fermenter-extractor employing a microporous hollow fiber membrane (MHF). This bioreactor system was operated
under a fed-batch mode with continuous removal of lactic acid by anin situ extraction. A tertiary amine (Alamine 336) was used as an extractant for lactic acid. The extraction capacity of Alamine
336 is greatly enhanced by addition of alcohol. Long-chain alcohols serve well for this purpose since they are less toxic
to micro-organism. Addition of kerosene, a diluent, was necessary to reduce the solvent viscosity. A solvent mixture of 20%
Alamine 336, 40% oleyl alcohol, and 40% kerosene was found to be most effective in the extraction of lactic acid. Progressive
change of pH from an initial value of 5.0 down to 4.3 has significantly improved the overall performance of the simultaneous
saccharification and extractive fermentation over that of constant pH operation. The change of pH was applied to promote cell
growth in the early phase, and extraction in the latter phase. 相似文献
9.
Chuanbin Liu Bo Hu Yan Liu Shulin Chen 《Applied biochemistry and biotechnology》1996,131(1-3):751-761
The production of nisin, a natural food preservative, by Lactococcus lactis subsp. lactis (ATCC 11454) is associated with the simultaneous formation of lactic acid during fermentation in a whey-based medium. As
a result of the low concentration and high separation cost of lactic acid, recovering lactic acid as a product may not be
economical, but its removal from the fermentation broth is important because the accumulation of lactic acid inhibits nisin
biosynthesis. In this study, lactic acid removal was accomplished by biological means. A mixed culture of L. lactis and Saccharomyces cerevisiae was established in order to stimulate the production of nisin via the in situ consumption of lactic acid by the yeast strain, which is capable of utilizing lactic acid as carbon source. The S. cerevisiae in the mixed culture did not compete with the nisin-producing bacteria because the yeast does not utilize lactose, the major
carbohydrate in whey for bacterial growth and nisin production. The results showed that lactic acid produced by the bacteria
was almost totally utilized by the yeast and the pH of the mixed culture could be maintained at around 6.0. Nisin production
by the mixed culture system reached 150.3 mg/L, which was 0.85 times higher than that by a pure culture of L. lactis. 相似文献
10.
Mycelial pellet formation by Rhizopus oryzae ATCC 20344 总被引:2,自引:0,他引:2
Factors in a cultivation medium affecting fungal growth morphology and funmaric acid production by Rhizopus oryzae ATCC 20344 were investigated. These factors included the initial pH value and trace metals such as zinc, magnesium, iron,
and manganese in the cultivation medium. It was found that a significant change in the growth morphology of R. oryzae ATCC 20344 occurs when the initial pH value is varied. A lower initial pH value in the cultivation medium was inhibitory
to fungal growth, and fast growth in the cultivation medium at a higher initial pH value promoted, the formation of large
pellets or filamentous forms. Trace metals in the cultivation media also had significant effects on pellet formation and fumaric
acid fermentation. 相似文献
11.
On-line monitoring of continuous beer fermentation process using automatic membrane inlet mass spectrometric system 总被引:1,自引:0,他引:1
A fully automatic membrane inlet mass spectrometric (MIMS) on-line instrumentation for the analysis of aroma compounds in continuous beer fermentation processes was constructed and tested. The instrumentation includes automatic filtration of the sample stream, flushing of all tubing between samples and pH control. The calibration standards can be measured periodically. The instrumentation has also an extra sample line that can be used for off-line sample collection or it can be connected to another on-line method. Detection limits for ethanol, acetic acid and eight organic beer aroma compounds were from μg l−1 to low mg l−1 levels and the standard deviations were less than 3.4%. The method has a good repeatability and linearity in the measurement range. Response times are shorter than or equal to 3 min for all compounds except for ethyl caproate, which has a response time of 8 min. In beer aroma compound analysis a good agreement between MIMS and static headspace gas chromatographic (HSGC) measurements was found. The effects of different matrix compounds commonly present in the fermentation media on the MIMS response to acetaldehyde, ethyl acetate and ethanol were studied. Addition of yeast did not have any effect on the MIMS response of ethanol or ethyl acetate. Sugars, glucose and xylose, increased the MIMS response of all studied analytes only slightly, whereas salts, ammonium chloride, ammonium nitrate and sodium chloride, increased the MIMS response of all three studied compounds prominently. The system was used for on-line monitoring of continuous beer fermentation with immobilised yeast. The results show that with MIMS it is possible to monitor the changes in the continuous process as well as delays in the two-phase process. 相似文献
12.
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
13.
In this technoeconomic evaluation of the manufacture of acetic acid by fermentation, the use of the bacterium:Acetobacter suboxydans from the old vinegar process was compared with expected performance of the newerClostridium thermoaceticum bacterium. Both systems were projected to operate as immobilized cells in a continuous, fluidized bed bioreactor, using solvent
extraction to recover the product.
Acetobacter metabolizes ethanol aerobically to produce acid at 100 g/L in a low pH medium. This ensures that the product is in the form
of a concentrated extractable free acid, rather than as an unextractable salt. Unfortunately, yields from glucose by way of
the ethanol fermentation are poor, but near the biological limits of the organisms involved. 相似文献
14.
The production of propionic acid by Propionibacterium freudenreichii CCTCC M207015 was investigated in a 7.5-l stirred-tank fermentor. Batch fermentations by P. freudenreichii CCTCC M207015 at various pH values ranging from 5.5 to 7.0 were studied. Based on the analysis of the time course of specific
cell growth rate (μ
x) and specific propionic acid formation rate (μ
p), a two-stage pH-shift control strategy was proposed. At first 48 h, pH was controlled at 6.5 to obtain the maximal μ
x, subsequently pH 6.0 was used to maintain high μ
p to enhance the production of propionic acid. By applying this pH-shift control strategy in propionic acid fermentation, the
maximal propionic acid and glucose conversion efficiency had a significant improvement and reached 19.21 g/l and 48.03%, respectively,
compared with those of constant pH operation (14.58 g/l and 36.45%). Fed-batch fermentation with pH-shift control strategy
was also applied to produce propionic acid; the maximal propionic acid yield and glucose conversion efficiency reached 25.23 g/l
and 47.76%, respectively. 相似文献
15.
This work represents a continuation of our investigation into environmental conditions that promote lactic acid synthesis
by Zymomonas mobilis. The characteristic near theoretical yield of ethanol from glucose by Z. mobilis can be compromised by the synthesis of d- and l-lactic acid. The production of lactic acid is exacerbated by the following conditions: pH 6.0, yeast extract, and reduced
growth rate. At a specific growth rate of 0.048/h, the average yield of dl-lactate from glucose in a yeast extract-based medium at pH 6.0 was 0.15 g/g. This represents a reduction in ethanol yield
of about 10% relative to the yield at a growth rate of 0.15/h. Very little lactic acid was produced at pH 5.0 or using a defined
salts medium (without yeast extract) Under permissive and comparable culture conditions, a tetracycline-resistant, d-ldh negative mutant produced about 50% less lactic acid than its parent strain Zm ATCC 39676. d-lactic acid was detected in the cell-free spent fermentation medium of the mutant, but this could be owing to the presence
of a racemase enzyme. Under the steady-state growth conditions provided by the chemostat, the specific rate of glucose consumption
was altered at a constant growth rate of 0.075/h. Shifting from glucose-limited to nitrogen-limited growth, or increasing
the temperature, caused an increase in the specific rate of glucose catabolism. There was good correlation between an increase
in glycolytic flux and a decrease in lactic acid yield from glucose. This study points to a mechanistic link between the glycolytic
flux and the control of end-product glucose metabolism. Implications of reduced glycolytic flux in pentose-fermenting recombinant
Z. mobilis strains, relative to increased byproduct synthesis, is discussed. 相似文献
16.
The microbiological production of organic acids by fermentation processes is growing in commercial importance. However, the removal of product and pH control are two main issues that limit the technical and commercial viability of such processes. A laboratory scale bioreactor combining conventional electrodialysis and bipolar membrane electrodialysis has been developed for in situ product removal and pH control in lactic acid fermentation. The electrokinetic process enabled removal of the biocatalytic product (lactic acid) directly from the bioreactor system, in a concentrated form, as well as enabling good pH control without generation of troublesome salts. Moreover, end-product inhibition of glucose catabolism was reduced, resulting in a greater generation of the end-product lactic acid. An automatic pH sensor and current application system was developed and successfully implemented for lactic acid fermentation in the electrokinetic bioreactor. 相似文献
17.
Yoshihiro Yamauchi Takanori Okamoto Hiroshi Murayama Akira Nagara Tadashi Kashihara Masasi Yoshida Tetsuji Yasui Koichi Nakanishi 《Applied biochemistry and biotechnology》1995,53(3):245-259
A multistage bioreactor system for rapid beer fermentation was developed. The main fermentation process, which conventionally
requires 7 d, could be shortened to 2 d by this system. The concentration of esters and higher alcohols are major factors
in brewery fermentation, their production being closely related to the yeast growth phase. Yeast metabolism was successfully
subdivided into a growth and a restricted phase through a combination of a continuous stirredtank reactor (CSTR) and an immobilized
yeast packed-bed reactor (PBR). Production of higher alcohols was high in the CSTR because of its association with the level
of biosynthetic activityde novo. A small amount was also produced in the PBR, however, possibly a result of an overflow in carbohydrate metabolism. Ester
formation mainly occurred in the PBR, a linear increase in the level of ester being observed with flow through the PBR. The
reactor system control strategy was to maximize the level of both higher alcohol and ester formation. The CSTR/PBR control
range, based on extract consumption, was varied between 1:1 and 1:2. A ratio of 1:1 tended to create a flat beer, whereas
a ratio 1:2 gave a beer of richer quality. Amino acid uptake by the yeast directly contributed to a reduction in the wort
pH, whereas no relation could be observed between the level of organic acid production and pH. 相似文献
18.
Actinobacillus succinogenes 130 Z was used to produce succinic acid from cheese whey in this study. At the presence of external CO2 supply, the effects of initial cheese whey concentration, pH, and inoculum size on the succinic acid production were studied.
The by-product formation during the fermentation process was also analyzed. The highest succinic acid yield of 0.57 was obtained
at initial cheese whey concentration of 50 g/L, while the highest succinic acid productivity of 0.58 g h−1 L−1 was obtained at initial cheese whey concentration of 100 g/L. Increase in pH and inoculum size caused higher succinic acid
yield and productivity. At the preferred fermentation condition of pH 6.8, inoculum size of 5% and initial cheese whey concentration
of 50 g/L, succinic acid yield of 0.57, and productivity of 0.44 g h−1 L−1 were obtained. Acetic acid and formic acid were the main by-products throughout the fermentation run of 48 h. It is feasible
to produce succinic acid using lactose from cheese whey as carbon resource by A. succinogenes 130 Z. 相似文献
19.
Eliana V. Canettieri João B. Almeida E. Silva Maria G. A. Felipe 《Applied biochemistry and biotechnology》2001,94(2):159-168
This study deals with the bioconversion of xylose into xylitol by Candida guilliermondii FTI 20037 using eucalyptus hemicellulosic hydrolysate obtained by acid hydrolysis. The influence of various parameters (ammonium
sulfate, rice bran, pH, and xylose concentration) on the production of xylitol was evaluated. The experiments were based on
multivariate statistical concepts, with the application of factorial design techniques to identify the most important variables
in the process. The levels of these variables were quantified by the response surface methodology, which permitted the establishment
of a significant mathematical model with a coefficient determination of R
2=0.92. The best results (xylitol=10.0 g/L, yield factor=0.2 g/g, and productivity=0.1 g/[L·h]) were attained with hydrolysate
containing ammonium sulfate (1.1 g/L), rice bran (5.0 g/L), and xylose (initial concentration of 60.0 g/L), after 72 h of
fermentation. The pH of fermentation was adjusted to 8.0 and the inoculum level utilized was 3 g/L. 相似文献
20.
Jian Zhang Ying Zhang Shan-na Liu Ye Han Zhi-jiang Zhou 《Applied biochemistry and biotechnology》2012,166(6):1388-1400
To investigate the effect of pH and temperature on the cell growth and bacteriocin production of Pediococcus acidilactici PA003, a lactic acid bacterium isolated from traditionally fermented cabbage, the kinetic behaviour of P. acidilactici PA003 was simulated in vitro during laboratory fermentations by making use of MRS broth. Firstly, primary models were developed
for cell growth, glucose consumption, lactic acid and bacteriocin production for a given set of environmental conditions.
Based on primary models, further study was undertaken to fit secondary models to describe the influence of temperature and
pH on microbial behaviour. The models were validated successfully for all components. The results from the cell yield coefficient
for lactic acid production reflected the homofermentative nature of P. acidilactici PA003. Both cell growth and bacteriocin production were very much influenced by changes in temperature and pH. The optimal
condition for specific growth rate and biomass concentration was almost the same at pH 6.5 and 35 °C. At 35 °C and pH 6.1,
the maximal bacteriocin activity was also achieved. The kinetic models provide useful tools for elucidating the mechanisms
of temperature and pH on the kinetic behaviour of P. acidilactici PA003. The information obtained in this paper may be very useful for the selection of suitable starter cultures for a particular
fermentation process and is a first step in the optimization of food fermentation processes and technology as well. 相似文献