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1.
Shiying Lu Mark A. Eiteman Elliot Altman 《Journal of industrial microbiology & biotechnology》2009,36(8):1101-1109
Succinate production was studied in Escherichia coli AFP111, which contains mutations in pyruvate formate lyase (pfl), lactate dehydrogenase (ldhA) and the phosphotransferase system glucosephosphotransferase enzyme II (ptsG). Two-phase fermentations using a defined medium at several controlled levels of pH were conducted in which an aerobic cell
growth phase was followed by an anaerobic succinate production phase using 100% (v/v) CO2. A pH of 6.4 yielded the highest specific succinate productivity. A metabolic flux analysis at a pH of 6.4 using 13C-labeled glucose showed that 61% of the PEP partitioned to oxaloacetate and 39% partitioned to pyruvate, while 93% of the
succinate was formed via the reductive arm of the TCA cycle. The flux distribution at a pH of 6.8 was also analyzed and was
not significantly different compared to that at a pH of 6.4. Ca(OH)2 was superior to NaOH or KOH as the base for controlling the pH. By maintaining the pH at 6.4 using 25% (w/v) Ca(OH)2, the process achieved an average succinate productivity of 1.42 g/l h with a yield of 0.61 g/g. 相似文献
2.
An Escherichia coli strain, JM109, was successfully engineered into an efficient hyaluronic acid (HA) producer by co-expressing the only known
class-II HA synthase from a Gram-negative bacterium (Pasteurella multocida) and uridine diphosphate-glucose dehydrogenase from E. coli K5 strain. The engineered strain produced about 0.5 g/L HA in shake flask culture and about 2.0–3.8 g/L in a fed-batch fermentation
process in a 1-L bioreactor. The sharp increase in viscosity associated with HA accumulation necessitated pure oxygen supplement
to maintain fermentation in aerobic regime. Precursor supply during HA synthesis was probed by glucosamine supplement, which
shortens biosynthesis pathway and eliminates one step requiring ATP. HA synthesis was increased with glucosamine supplement
from 2.7 to 3.7 g/L (37%), which was mirrored with a concomitant 42% decrease in pure oxygen input, suggesting a close connection
between energy metabolism and precursor supply. Decoupling HA synthesis from cell growth by using fosfomycin (an inhibitor
for cell wall synthesis) led to a 70% increase in HA synthesis, suggesting detrimental effects on HA synthesis from cell growth
via precursor competition. This study demonstrates a potentially viable process for HA based on a recombinant E. coli strain. In addition, the precursor supply limitation identified in this study suggests new engineering targets in subsequent
metabolic engineering efforts. 相似文献
3.
Succinate production in dual-phase Escherichia coli fermentations depends on the time of transition from aerobic to anaerobic conditions 总被引:1,自引:0,他引:1
Vemuri GN Eiteman MA Altman E 《Journal of industrial microbiology & biotechnology》2002,28(6):325-332
We examined succinic acid production in Escherichia coli AFP111 using dual-phase fermentations, which comprise an initial aerobic growth phase followed by an anaerobic production
phase. AFP111 has mutations in the pfl, ldhA, and ptsG genes, and we additionally transformed this strain with the pyc gene (AFP111/pTrc99A-pyc) to provide metabolic flexibility at the pyruvate node. Aerobic fermentations with these two strains were completed to catalog
physiological states during aerobic growth that might influence succinate generation in the anaerobic phase. Activities of
six key enzymes were also determined for these aerobic fermentations. From these results, six transition times based on physiological
states were selected for studying dual-phase fermentations. The final succinate yield and productivity depend greatly on the
physiological state of the cells at the time of transition. Using the best transition time, fermentations achieved a final
succinic acid concentration of 99.2 g/l with an overall yield of 110% and productivity of 1.3 g/l h. Journal of Industrial Microbiology & Biotechnology (2002) 28, 325–332 DOI: 10.1038/sj/jim/7000250
Received 01 October 2001/ Accepted in revised form 12 March 2002 相似文献
4.
Efficient utilization of pentose sugars (xylose and arabinose) is an essential requirement for economically viable ethanol
production from cellulosic biomass. The desirable pentose-fermenting ethanologenic biocatalysts are the native microorganisms
or the engineered derivatives without recruited exogenous gene(s). We have used a metabolic evolution (adaptive selection)
approach to improve a non-transgenic homoethanol Escherichia coli SZ420 (ldhA pflB ackA frdBC pdhR::pflBp6-aceEF-lpd) for xylose fermentation. An improved mutant, E. coli KC01, was evolved through a 3 month metabolic evolution process. This evolved mutant increased pyruvate dehydrogenase activity
by 100%, cell growth rate (h−1) by 23%, volumetric ethanol productivity by 65% and ethanol tolerance by 200%. These improvements enabled KC01 to complete
50 g xylose l−1 fermentations with an ethanol titer of 23 g l−1 and a yield of 90%. The improved cell growth and ethanol production of KC01 are likely attributed to its three fold increased
ethanol tolerance. 相似文献
5.
Liu R Liang L Chen K Ma J Jiang M Wei P Ouyang P 《Applied microbiology and biotechnology》2012,94(4):959-968
In Escherichia coli K12, succinate was not the dominant fermentation product from xylose. To reduce by-product formation and increase succinate
accumulation, pyruvate formate lyase and lactate dehydrogenase, encoded by pflB and ldhA genes, were inactivated. However, these mutations eliminated cell growth and xylose utilization. During anaerobic growth
of bacteria, organic intermediates, such as pyruvate, serve as electron acceptors to maintain the overall redox balance. Under
these conditions, the ATP needed for cell growth is derived from substrate level phosphorylation. In E. coli K12, conversion of xylose to pyruvate only yielded 0.67 net ATP per xylose during anaerobic fermentation. However, E. coli produces equimolar amounts of acetate and ethanol from two pyruvates, and these reactions generate one additional ATP. Conversion
of xylose to acetate and ethanol increases the net ATP yield from 0.67 to 1.5 per xylose, which could meet the ATP needed
for xylose metabolism. A pflB deletion strain cannot convert pyruvate to acetyl coenzyme A, the precursor for acetate and ethanol production, and could
not produce the additional ATP. Thus, the double mutations eliminated cell growth and xylose utilization. To supply the sufficient
ATPs, overexpression of ATP-forming phosphoenolpyruvate-carboxykinase from Bacillus subtilis 168 in an ldhA, pflB, and ppc deletion strain resulted in a significant increase in cell mass and succinate production. In addition, fermentation of corn
stalk hydrolysate containing a high percentage of xylose and glucose produced a final succinate concentration of 11.13 g l−1 with a yield of 1.02 g g−1 total sugars during anaerobic fermentation. 相似文献
6.
Amani Briki Karim Kabor Eric Olmos Sabine Bosselaar Fabrice Blanchard Michel Fick Emmanuel Guedon Frantz Fournier Stphane Delaunay 《Engineering in Life Science》2020,20(5-6):205-215
Corynebacterium glutamicum is well known as an important industrial amino acid producer. For a few years, its ability to produce organic acids, under micro‐aerobic or anaerobic conditions was demonstrated. This study is focused on the identification of the culture parameters influencing the organic acids production and, in particular, the succinate production, by this bacterium. Corynebacterium glutamicum 2262, used throughout this study, was a wild‐type strain, which was not genetically designed for the production of succinate. The oxygenation level and the residual glucose concentration appeared as two critical parameters for the organic acids production. The maximal succinate concentration (4.9 g L?1) corresponded to the lower kLa value of 5 h?1. Above 5 h?1, a transient accumulation of the succinate was observed. Interestingly, the stop in the succinate production was concomitant with a lower threshold glucose concentration of 9 g L?1. Taking into account this threshold, a fed‐batch culture was performed to optimize the succinate production with C. glutamicum 2262. The results showed that this wild‐type strain was able to produce 93.6 g L?1 of succinate, which is one of the highest concentration reported in the literature. 相似文献
7.
Bashir Sajo Mienda 《Journal of biomolecular structure & dynamics》2013,31(14):3680-3686
Genome-scale metabolic model (GEM) of Escherichia coli has been published with applications in predicting metabolic engineering capabilities on different carbon sources and directing biological discovery. The use of glycerol as an alternative carbon source is economically viable in biorefinery. The use of GEM for predicting metabolic gene deletion of lactate dehydrogenase (ldhA) for increasing succinate production in Escherichia coli from glycerol carbon source remained largely unexplored. Here, I hypothesized that metabolic gene knockout of ldhA in E. coli from glycerol could increase succinate production. A proof-of-principle strain was constructed and designated as E. coli BMS5 (ΔldhA), by predicting increased succinate production in E. coli GEM and confirmed the predicted outcomes using wet cell experiments. The mutant GEM (ΔldhA) predicted 11% increase in succinate production from glycerol compared to its wild-type model (iAF1260), and the E. coli BMS5 (ΔldhA) showed 1.05 g/l and its corresponding wild-type produced .05 g/l (23-fold increase). The proof-of-principle strain constructed in this study confirmed the aforementioned hypothesis and further elucidated the fact that E. coli GEM can prospectively and effectively predict metabolic engineering interventions using glycerol as substrate and could serve as platform for new strain design strategies and biological discovery. 相似文献
8.
Lu J Tang J Liu Y Zhu X Zhang T Zhang X 《Applied microbiology and biotechnology》2012,93(6):2455-2462
Phosphoenolpyruvate (PEP) is an important precursor for anaerobic production of succinate and malate. Although inactivating
PEP/carbohydrate phosphotransferase systems (PTS) could increase PEP supply, the resulting strain had a low glucose utilization
rate. In order to improve anaerobic glucose utilization rate for efficient production of succinate and malate, combinatorial
modulation of galactose permease (galP) and glucokinase (glk) gene expression was carried out in chromosome of an Escherichia coli strain with inactivated PTS. Libraries of artificial regulatory parts, including promoter and messenger RNA stabilizing region
(mRS), were firstly constructed in front of β-galactosidase gene (lacZ) in E. coli chromosome through λ-Red recombination. Most regulatory parts selected from mRS library had constitutive strengths under
different cultivation conditions. A convenient one-step recombination method was then used to modulate galP and glk gene expression with different regulatory parts. Glucose utilization rates of strains modulated with either galP or glk all increased, and the rates had a positive relation with expression strength of both genes. Combinatorial modulation had
a synergistic effect on glucose utilization rate. The highest rate (1.64 g/L h) was tenfold higher than PTS− strain and 39% higher than the wild-type E. coli. These modulated strains could be used for efficient anaerobic production of succinate and malate. 相似文献
9.
Ma JF Jiang M Chen KQ Xu B Liu SW Wei P Ying HJ Chang HN Ouyang PK 《Bioprocess and biosystems engineering》2011,34(4):411-418
Escherichia coli AFP111, a pflB, ldhA, ptsG triple mutant of E. coli W1485, can be recovered for additional succinate production in fresh medium after two-stage fermentation (an aerobic growth
stage followed by an anaerobic production stage). However, the specific productivity is lower than that of two-stage fermentation.
In this study, three strategies were compared for reusing the cells. It was found when cells were aerobically cultivated at
the end of two-stage fermentation without supplementing any carbon source, metabolites (mainly succinate and acetate) could
be consumed. As a result, enzyme activities involved in the reductive arm of tricarboxylic acid cycle and the glyoxylate shunt
were enhanced, yielding a succinate specific productivity above
1 2 5 \textmg \textgDCW - 1 \texth - 1 1 2 5\;{\text{mg}}\;{\text{g}}_{\rm DCW}^{ - 1} \,{\text{h}}^{ - 1} and a mass yield above 0.90 g g−1 in the subsequent anaerobic fermentation. In addition, the intracellular NADH of cells subjected to aerobic cultivation with
metabolites increased by more than 3.6 times and the ratio of NADH to NAD+ increased from 0.4 to 1.3, which were both favorable for driving the TCA branch to succinate. 相似文献
10.
Artificial amplification of gluconeogenic phosphoenolpyruvate carboxykinase (PCK) under glycolytic conditions enables Escherichia coli to maintain a greater intracellular ATP concentration during its growth phase. To demonstrate the biotechnological benefit
of E. coli harboring a high intracellular ATP concentration, we compared the recombinant protein synthesis of a soluble protein (enhanced
green fluorescence protein, GFP) with that of a secretory protein (alkaline protease, AP), under control of the T7 promoter
in E. coli BL21(DE3) overexpressing PCK. According to the batch fermentations, the strain overexpressing PCK produced more GFP and AP
with a lower increase in biomass than the control strain. In a chemostat culture (D = 0.7 h−1), the GFP production in the PCK overexpressing strain was 99.0 ± 4.31 mg/g cell, with a biomass of 0.22 g/L, while that of
the control strain was 53.5 ± 3.07 mg/g cell, with a biomass of 0.35 g/L. These results indicate that the PCK overexpressing
E. coli strain harboring high intracellular levels of ATP can be useful as a protein-synthesizing host. The potential uses of the
strain and associated rationale are discussed. 相似文献
11.
Succinate production from xylose‐glucose mixtures using a consortium of engineered Escherichia coli
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The conversion of variable sugar mixtures into biochemicals poses a challenge for a single microorganism. For example, succinate has not been effectively generated from mixtures of glucose and xylose. In this work, a consortium of two Escherichia coli strains converted xylose and glucose to succinate in a dual phase aerobic/anaerobic process. First, the optimal pathway from xylose or glucose to succinate was determined by expressing either heterologous pyruvate carboxylase or heterologous adenosine triphosphate‐forming phosphoenol pyruvate (PEP) carboxykinase. Expression of PEP carboxykinase (pck) resulted in higher yield (0.86 g/g) and specific productivity (155 mg/gh) for xylose conversion, while expression of pyruvate carboxylase (pyc) resulted in higher productivity (76 mg/gh) for glucose conversion. Then, processes using consortia of the two optimal xylose‐selective and glucose‐selective strains were designed for two different feed ratios of glucose/xylose. In each case the consortia generated over 40 g/L succinate efficiently with yields greater than 0.90 g succinate/g total sugar. This study demonstrates two advantages of microbial consortia for the conversion of sugar mixtures: each sugar‐to‐product pathway can be optimized independently, and the volumetric consumption rate for each sugar can be controlled independently, for example, by altering the biomass concentration of each consortium member strain. 相似文献
12.
Phloroglucinol is a valuable chemical which has been successfully produced by metabolically engineered Escherichia coli. However, the low productivity remains a bottleneck for large-scale application and cost-effective production. In the present
work, we cloned the key biosynthetic gene, phlD (a type III polyketide synthase), into a bacterial expression vector to produce phloroglucinol in E. coli and developed different strategies to re-engineer the recombinant strain for robust synthesis of phloroglucinol. Overexpression
of E. coli marA (multiple antibiotic resistance) gene enhanced phloroglucinol resistance and elevated phloroglucinol production to 0.27 g/g
dry cell weight. Augmentation of the intracellular malonyl coenzyme A (malonyl-CoA) level through coordinated expression of
four acetyl-CoA carboxylase (ACCase) subunits increased phloroglucinol production to around 0.27 g/g dry cell weight. Furthermore, the coexpression of ACCase and marA caused another marked improvement in phloroglucinol production 0.45 g/g dry cell weight, that is, 3.3-fold to the original
strain. Under fed-batch conditions, this finally engineered strain accumulated phloroglucinol up to 3.8 g/L in the culture
12 h after induction, corresponding to a volumetric productivity of 0.32 g/L/h. This result was the highest phloroglucinol
production to date and showed promising to make the bioprocess economically feasible. 相似文献
13.
In this study, the glucose 6-phosphate dehydrogenase gene (XOO2314) was inactivated in order to modulate the intracellular
glucose 6-phosphate, and its effects on xanthan production in a wild-type strain of Xanthomonas oryzae were evaluated. The intracellular glucose 6-phosphate was increased from 17.6 to 99.4 μmol g−1 (dry cell weight) in the gene-disrupted mutant strain. The concomitant increase in the glucose 6-phosphate was accompanied
by an increase in xanthan production of up to 2.23 g l−1 (culture medium). However, in defined medium supplemented with 0.4% glucose, the growth rate of the mutant strain was reduced
to 52.9% of the wild-type level. Subsequently, when a family B ATP-dependent phosphofructokinase from Escherichia coli was overexpressed in the mutant strain, the growth rate was increased to 142.9%, whereas the yields of xanthan per mole of
glucose remained approximately the same. 相似文献
14.
Jens Kastenhofer Lukas Rettenbacher Lukas Feuchtenhofer Juergen Mairhofer Oliver Spadiut 《Biotechnology journal》2021,16(3):2000274
With the growing interest in continuous cultivation of Escherichia coli, secretion of product to the medium is not only a benefit, but a necessity in future bioprocessing. In this study, it is shown that induced decoupling of growth and heterologous gene expression in the E. coli X-press strain (derived from BL21(DE3)) facilitates extracellular recombinant protein production. The effect of the process parameters temperature and specific glucose consumption rate (qS) on growth, productivity, lysis and leakiness, is investigated, to find the parameter space allowing extracellular protein production. Two model proteins are used, Protein A (SpA) and a heavy-chain single-domain antibody (VHH), and performance is compared to the industrial standard strain BL21(DE3). It is shown that inducible growth repression in the X-press strain greatly mitigates the effect of metabolic burden under different process conditions. Furthermore, temperature and qS are used to control productivity and leakiness. In the X-press strain, extracellular SpA and VHH titer reach up to 349 and 19.6 mg g−1, respectively, comprising up to 90% of the total soluble product, while keeping cell lysis at a minimum. The findings demonstrate that the X-press strain constitutes a valuable host for extracellular production of recombinant protein with E. coli. 相似文献
15.
Glycerol has become an ideal feedstock for the microbial production of bio-based chemicals due to its abundance, low cost, and high degree of reduction. We have previously reported the pathways and mechanisms for the utilization of glycerol by Escherichia coli in minimal salts medium under microaerobic conditions. Here we capitalize on such results to engineer E. coli for the production of value-added succinate from glycerol. Through metabolic engineering of E. coli metabolism, succinate production was greatly elevated by (1) blocking pathways for the synthesis of competing by-products lactate, ethanol, and acetate and (2) expressing Lactococcus lactis pyruvate carboxylase to drive the generation of succinate from the pyruvate node (as opposed to that of phosphoenolpyruvate). As such, these metabolic engineering strategies coupled cell growth to succinate production because the synthesis of succinate remained as the primary route of NAD+ regeneration. This feature enabled the operation of the succinate pathway in the absence of selective pressure (e.g. antibiotics). Our biocatalysts demonstrated a maximum specific productivity of ~400 mg succinate/gcell/h and a yield of 0.69 g succinate/g glycerol, on par with the use of glucose as a feedstock. 相似文献
16.
To understand the metabolic characteristics of Clostridium acetobutylicum and to examine the potential for enhanced butanol production, we reconstructed the genome-scale metabolic network from its
annotated genomic sequence and analyzed strategies to improve its butanol production. The generated reconstructed network
consists of 502 reactions and 479 metabolites and was used as the basis for an in silico model that could compute metabolic and growth performance for comparison with fermentation data. The in silico model successfully predicted metabolic fluxes during the acidogenic phase using classical flux balance analysis. Nonlinear
programming was used to predict metabolic fluxes during the solventogenic phase. In addition, essential genes were predicted
via single gene deletion studies. This genome-scale in silico metabolic model of C. acetobutylicum should be useful for genome-wide metabolic analysis as well as strain development for improving production of biochemicals,
including butanol.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
J. L. and H. Y. equally contributed to this work. 相似文献
17.
Succinate production under different concentrations of carbon dioxide (CO2) was studied in Escherichia coli AFP111, which contains mutations in pyruvate formate lyase (pfl), lactate dehydrogenase (ldhA) and the phosphotransferase system glucosephosphotransferase enzyme II (ptsG). A series of two-phase fermentations were conducted in which an aerobic cell growth phase was followed by an anaerobic succinate production phase using several constant concentrations of CO2. As the concentration of CO2 in the gas phase increased from 0% to 50%, the succinate specific productivity increased from 1.9 mg/g h to 225 mg/g h, and the succinate yield increased from 0.04 g/g to 0.75 g/g. Above 50% CO2, succinate production did not increase further. Intracellular fluxes were determined at three different CO2 concentrations (3%, 10%, and 50%) using 13C-label tracing coupled with LC–MS analysis. The fraction of carbon flux into the pentose phosphate pathway increased from 0.04 at 3% CO2 to 0.17 at 50% CO2. Also, the fractional flux through anaplerotic carboxylation at the phosphoenolpyruvate (PEP) node increased slightly from 0.53 at 3% CO2 to 0.63 at 50% CO2. The increased flux into the pentose phosphate pathway is attributed to an increased demand for reduced cofactors with elevated CO2. A four-process explicit model to describe the CO2 transfer and utilization was proposed. The model predicted that at CO2 concentrations below about 30–40% the system becomes limited by gas phase CO2, while at higher CO2 concentrations the system is limited by PEP carboxylase enzyme kinetics. 相似文献
18.
Ziyu Zhu Xiaoqian Chen Wenhao Li Yingping Zhuang Yuzheng Zhao Guan Wang 《Biotechnology progress》2023,39(4):e3352
The strategy of temperature downshift has been widely used in the biopharmaceutical industry to improve antibody production and cell-specific production rate (qp) with Chinese hamster ovary cells (CHO). However, the mechanism of temperature-induced metabolic rearrangement, especially important intracellular metabolic events, remains poorly understood. In this work, in order to explore the mechanisms of temperature-induced cell metabolism, we systematically assessed the differences in cell growth, antibody expression, and antibody quality between high-producing (HP) and low-producing (LP) CHO cell lines under both constant temperature (37°C) and temperature downshift (37°C→33°C) settings during fed-batch culture. Although the results showed that low-temperature culture during the late phase of exponential cell growth significantly reduced the maximum viable cell density (p < 0.05) and induced cell cycle arrest in the G0/G1 phase, this temperature downshift led to a higher cellular viability and increased antibody titer by 48% and 28% in HP and LP CHO cell cultures, respectively (p < 0.001), and favored antibody quality reflected in reduced charge heterogeneity and molecular size heterogeneity. Combined extra- and intra-cellular metabolomics analyses revealed that temperature downshift significantly downregulated intracellular glycolytic and lipid metabolic pathways while upregulated tricarboxylic acid (TCA) cycle, and particularly featured upregulated glutathione metabolic pathways. Interestingly, all these metabolic pathways were closely associated with the maintenance of intracellular redox state and oxidative stress-alleviating strategies. To experimentally address this, we developed two high-performance fluorescent biosensors, denoted SoNar and iNap1, for real-time monitoring of intracellular nicotinamide adenine dinucleotide/nicotinamide adenine dinucleotide + hydrogen (NAD+/NADH) ratio and nicotinamide adenine dinucleotide phosphate (NADPH) amount, respectively. Consistent with such metabolic rearrangements, the results showed that temperature downshift decreased the intracellular NAD+/NADH ratio, which might be ascribed to the re-consumption of lactate, and increased the intracellular NADPH amount (p < 0.01) to scavenge intracellular reactive oxygen species (ROS) induced by the increased metabolic requirements for high-level expression of antibody. Collectively, this study provides a metabolic map of cellular metabolic rearrangement induced by temperature downshift and demonstrates the feasibility of real-time fluorescent biosensors for biological processes, thus potentially providing a new strategy for dynamic optimization of antibody production processes. 相似文献
19.
Corynebacterium glutamicum is known to produce organic acids under anaerobic culture conditions, in particular, lactic, succinic, and acetic acids. Our study is focused on acetic and succinic acid production using a lactate dehydrogenase-deficient strain of C. glutamicum. Usually, with this bacterium, the organic acid production process is based on an initial aerobic growth phase, followed by a rapid deoxygenation and an anaerobic production phase. In our study, we demonstrated that this strategy was unfavorable for the production of organic acids. Conversely, we showed that applying the best transition strategy based on progressive deoxygenation significantly increased the concentration of organic acids up to 640%. This was observed either by applying controlled dissolved oxygen concentrations or by decreasing the steps of gas flow rates. Our results also showed that applying constant oxygen transfer flux throughout the culture, and thus in the absence of the anaerobic phase, promoted constant production yields (approximately 0.5 mol of succinate or acetate per mole of glucose). In this case, acetate production (120 mM) was favored over succinate production (132 mM), resulting in a decrease in the molar ratio of products (succinate/acetate) from 4.8 to 1.1 between progressive deoxygenation and constant OTR cultures. 相似文献
20.
Keita Fukui Kei Nanatani Yoshihiko Hara Suguru Yamakami Daiki Yahagi Akito Chinen 《Bioscience, biotechnology, and biochemistry》2017,81(9):1837-1844
Under anaerobic conditions, Escherichia coli produces succinate from glucose via the reductive tricarboxylic acid cycle. To date, however, no genes encoding succinate exporters have been established in E. coli. Therefore, we attempted to identify genes encoding succinate exporters by screening an E. coli MG1655 genome library. We identified the yjjPB genes as candidates encoding a succinate transporter, which enhanced succinate production in Pantoea ananatis under aerobic conditions. A complementation assay conducted in Corynebacterium glutamicum strain AJ110655ΔsucE1 demonstrated that both YjjP and YjjB are required for the restoration of succinate production. Furthermore, deletion of yjjPB decreased succinate production in E. coli by 70% under anaerobic conditions. Taken together, these results suggest that YjjPB constitutes a succinate transporter in E. coli and that the products of both genes are required for succinate export. 相似文献