Regulation of intracellular level of ATP and NADH in Escherichia coli to promote succinic acid production / 生物工程学报

Succinic acid is an important C4 platform chemical that is widely used in food, chemical, medicine sectors. The bottleneck of fermentative production of succinic acid by engineered Escherichia coli is the imbalance of intracellular cofactors, which often leads to accumulation of by-products, lower yield and low productivity. Stoichiometric analysis indicated that an efficient production of succinic acid by E. coli FMME-N-26 under micro-aeration conditions might be achieved when the TCA cycle provides enough ATP and NADH for the r-TCA pathway. In order to promote succinic acid production, a serial of metabolic engineering strategies include reducing ATP consumption, strengthening ATP synthesis, blocking NADH competitive pathway and constructing NADH complementary pathway were developed. As result, an engineered E. coli FW-17 capable of producing 139.52 g/L succinic acid and 1.40 g/L acetic acid in 5 L fermenter, which were 17.81% higher and 67.59% lower than that of the control strain, was developed. Further scale-up experiments were carried out in a 1 000 L fermenter, and the titer of succinic acid and acetic acid were 140.2 g/L and 1.38 g/L, respectively.

α-Tocopheryl Succinate Inhibits Osteolytic Bone Metastasis of Breast Cancer by Suppressing Migration of Cancer Cells and Receptor Activator of Nuclear Factor-κB Ligand Expression of Osteoblasts

BACKGROUND: Breast cancer is one of the most common cancers affecting women and has a high incidence of bone metastasis, causing osteolytic lesions. The elevated expression of receptor activator of nuclear factor-κB ligand (RANKL) in cancer activates osteoclasts, leading to bone destruction. We previously reported that α-tocopheryl succinate (αTP-suc) inhibited interleukin-1-induced RANKL expression in osteoblasts. Here, we examined the effect of αTP-suc on osteolytic bone metastasis in breast cancer. METHODS: To examine the effect of αTP-suc on the metastatic capacity of breast cancer, MDA-MB-231-FL cells were injected into the left cardiac ventricle of BALB/c nude mice along with intraperitoneal injection of αTP-suc. The mice were then analyzed by bioluminescence imaging. To investigate the effect of αTP-suc on osteolysis, 4T1 cells were directly injected into the femur of BALB/c mice along with intraperitoneal injection of αTP-suc. Microcomputed tomography analysis and histomorphometric analysis of the femora were performed. RESULTS: αTP-suc inhibited cell migration and cell growth of 4T1 cells. In line with these results, bone metastasis of MDA-MB-231-FL cells was reduced in mice injected with αTP-suc. In addition, αTP-suc decreased osteoclastogenesis by inhibiting 4T1-induced RANKL expression in osteoblasts. Consistent with these results, 4T1-induced bone destruction was ameliorated by αTP-suc, with in vivo analysis showing reduced tumor burden and osteoclast numbers. CONCLUSIONS: Our findings suggest that αTP-suc may be efficiently utilized to prevent and treat osteolytic bone metastasis of breast cancer with dual effects.

Effect of Thermoresponsive Poly(L-lactic acid)-poly (ethylene glycol) Gel Injection on Left Ventricular Remodeling in a Rat Myocardial Infarction Model

Some gel types have been reported to prevent left ventricular (LV) remodeling in myocardial infarction (MI) animal models. In this study, we tested biodegradable thermoresponsive gels. Poly(L-lactic acid)-poly(ethylene glycol) (PLLA-PEG) and poly(D-lactic acid)-poly(ethylene glycol) (PDLA-PEG) were synthesized by the polycondensation of Land D-lactic acids in the presence of PEG and succinic acid. Each of these block copolymers was used to prepare particles dispersed in an aqueous medium and mixed together to obtain a PLLA-PEG/PDLA-PEG suspension, which was found to show a sol-to-gel transition around the body temperature by the stereocomplex formation of enantiomeric PLLA and PDLA sequences. In the present study, the G' of the PLLA-PEG/PDLA-PEG suspension in the rheological measurement remained as low as 1 Pa at 20 ℃ and increased 2 kPa at 37 ℃. The sol-gel systems of PLLA-PEG/PDLA-PEG might be applicable to gel therapy. The effect of the PLLA-PEG/PDLA-PEG gel injection was compared with that of a calciumcrosslinked alginate gel and saline in a rat MI model. The percent fractional shortening improved in the PLLA-PEG/ PDLA-PEG (20.8 ± 4.1%) and alginate gel (21.1 ± 4.8%) compared with the saline (14.2 ± 2.8%) with regard to the echocardiograph 4 weeks after the injection (p<0.05). There were reduced infarct sizes in both PLLA-PEG/PDLA-PEG gel and alginate gel compared with the saline injection (p<0.05). Moreover, a greater reduction in LV cavity area was observed with the PLLA-PEG/PDLA-PEG gel than with the alginate gel (p = 0.06). These results suggest that the PLLA- PEG/PDLA-PEG gel should have high therapeutic potential in gel therapy for LV remodeling after MI.

Improved in vitro and in vivo performance of carbamazepine enabled by using a succinic acid cocrystal in a stable suspension formulation

Currently cocrystals are considered as an established approach for making crystalline solids with overall improved physico-chemical properties. However, some otherwise well behaving cocrystals undergo rapid dissociation during dissolution, with ultimate conversion to parent drug and thus apparent loss of improved solubility. The polymeric carriers are long known to manipulate this conversion during dissolution to parent crystalline drug, which may hinder or accelerate the dissolution process if used in a dosage form. The goal of this study was to deliver in vivo a more soluble carbamazepine-succinic acid [CBZ-SUC] cocrystal in suspension formulation utilizing Hydroxypropyl methyl cellulose [HPMC-AS] as a crystallization inhibitor and Polyvinyl carpolactam-polyvinyl acetate-polyethylene glycol graft co-polymer® as solubilizer. The concentration of these polymers were systemically varied during in vitro dissolution studies, while selected formulations from dissolution studies were tested in vivo. Pharmacokinetic studies [PK] in rabbits demonstrated that formulation F-X [1% cocrystal, 1% HPMC-AS and 2% Polyvinyl carpolactam-polyvinyl acetate-polyethylene glycol graft co-polymer caused almost 6fold improvement in AUCo-72 as well as much higher C[MAX] of 4.73microg.mL[+1] to that of l.OTmicrog.mL[+1] of unformulated 'neat' cocrystal given orally. When reference formulation of CBZ [F5-X] with similar composition to F-X were given to rabbits, cocrystal formulation gave 1.37fold bioavailability than CBZ reference formulation. C[MAX] of reference formulation observed was 3.9microg.mL

Immediate-type hypersensitivity response to systemic hydrocortisone sodium succinate

Immediate-type hypersensitivity responses to systemic corticosteroids are rare despite their widespread use. It is still controversial whether the responses rarely occur or are underdiagnosed in clinical settings. Many cases probably remain underdiagnosed because the symptoms often mimic symptoms of underlying diseases. This case report describes a 73-year-old man who had immediate hypersensitivity reactions after intravenous administration of hydrocortisone, which was primarily intended to prevent hypersensitivity reactions to contrast media. Whole body rash with pruritus developed shortly after the steroid injection. Since the patient already experienced rash and itching sense after contrast media and antihistamine injection, we conducted skin testing to figure out which drug triggered the hypersensitivity reactions. Intradermal skin tests revealed a positive response to hydrocortisone sodium succinate, which suggested his hypersensitivity reactions were developed by hydrocortisone. Being a common therapy for allergic reaction, corticosteroids themselves are rarely suspected of causing hypersensitivity reactions. Considering there is no typical symptom or standard diagnostic test, awareness of corticosteroid hypersensitivity reactions is of importance to make the diagnosis.

Current status of bio-based materials industry in China / 生物工程学报

In recent years, bio-based materials are becoming a new dominant industry leading the scientific and technological innovation, and economic development of the world. We reviewed the new development of bio-based materials industry in China, analyzed the entire market of bio-based materials products comprehensively, and also stated the industry status of bio-based chemicals, such as lactic acid, 1,3-propanediol, and succinic acid; biodegradable bio-based polymers, such as co-polyester of diacid and diol, polylactic acid, carbon dioxide based copolymer, polyhydroxyalknoates, polycaprolactone, and thermoplastic bio-based plastics; non-biodegradable bio-based polymers, such as bio-based polyamide, polytrimethylene terephthalate, bio-based polyurethane, and bio-based fibers.

Protective effect of succinic acid on cerebellar Purkinje cells of neonatal rats with convulsion / 中国当代儿科杂志

<p><b>OBJECTIVE</b>To investigate the protective effect of succinic acid (SA) on the cerebellar Purkinje cells (PCs) of neonatal rats with convulsion.</p><p><b>METHODS</b>A total of 120 healthy neonatal Sprague-Dawley rats aged 7 days were randomly divided into a neonatal period group and a developmental period group. Each of the two groups were further divided into 6 sub-groups: normal control, convulsion model, low-dose phenobarbital (PB) (30 mg/kg), high-dose PB (120 mg/kg), low-dose SA (30 mg/kg), and high-dose SA (120 mg/kg). Intraperitoneal injection of pentylenetetrazole was performed to establish the convulsion model. The normal control group was treated with normal saline instead. The rats in the neonatal group were sacrificed at 30 minutes after the injection of PB, SA, or normal saline, and the cerebellum was obtained. Those in the developmental group were sacrificed 30 days after the injection of PB, SA, or normal saline, and the cerebellum was obtained. Whole cell patch clamp technique was used to record the action potential (AP) of PCs in the cerebellar slices of neonatal rats; the parallel fibers (PF) were stimulated at a low frequency to induce excitatory postsynaptic current (EPSC). The effect of SA on long-term depression (LTD) of PCs was observed.</p><p><b>RESULTS</b>Compared with the normal control groups, the neonatal and developmental rats with convulsion had a significantly higher AP frequency of PCs (P<0.05), and the developmental rats with convulsion had a significantly decreased threshold stimulus (P<0.01) and a significantly greater inhibition of the amplitude of EPSC in PCs (P<0.05). Compared with the normal control groups, the neonatal and developmental rats with convulsion in the high-dose PB groups had a significantly decreased threshold stimulus (P<0.01), a significantly higher AP frequency of PCs (P<0.05), and a significantly greater inhibition of EPSC in PCs (P<0.05). Compared with the neonatal and developmental rats in the convulsion model groups, those in the high-dose SA groups had a significantly decreased AP frequency of PCs (P<0.05). The developmental rats in the low- and high-dose SA groups had a significantly higher AP threshold than those in the convulsion model group (P<0.05).</p><p><b>CONCLUSIONS</b>The high excitability of PCs and the abnormal PF-PC synaptic plasticity caused by convulsion in neonatal rats may last to the developmental period, which can be aggravated by PB, while SA can reduce the excitability of PCs in neonatal rats with convulsion and repair the short- and long-term abnormalities of LTD of PCs caused by convulsion.</p>

Research and industrialization of biobased materials in China / 生物工程学报

This paper reviews the research and commercialization progresses of biobased polymeric materials including polyhydroxyalkanoates (PHA), polylactides (PLA), poly (butylene succinate) (PBS) and its monomer succinate, and CO2 copolymer poly (propylene carbonate), especially these efforts made in China.

Succinic acid production from sucrose and sugarcane molasses by metabolically engineered Escherichia coli / 生物工程学报

Sugarcane molasses containing large amounts of sucrose is an economical substrate for succinic acid production. However, Escherichia coli AFP111 cannot metabolize sucrose although it is a promising candidate for succinic acid production. To achieve sucrose utilizing ability, we cloned and expressed cscBKA genes encoding sucrose permease, fructokinase and invertase of non-PTS sucrose-utilization system from E. coli W in E. coli AFP111 to generate a recombinant strain AFP111/pMD19T-cscBKA. After 72 h of anaerobic fermentation of the recombinant in serum bottles, 20 g/L sucrose was consumed and 12 g/L succinic acid was produced. During dual-phase fermentation comprised of initial aerobic growth phase followed by anaerobic fermentation phase, the concentration of succinic acid from sucrose and sugarcane molasses was 34 g/L and 30 g/L, respectively, at 30 h of anaerobic phase in a 3 L fermentor. The results show that the introduction of non-PTS sucrose-utilization system has sucrose-metabolizing capability for cell growth and succinic acid production, and can use cheap sugarcane molasses to produce succinic acid.

Health impact assessment of decreases in PM10 and ozone concentrations in the Mexico City Metropolitan Area: A basis for a new air quality management program / Evaluación de impacto en salud ante reducciones de PM10 y ozono en la Zona Metropolitana del Valle de México: Base para un nuevo programa de calidad del aire

Objective. To conduct a health impact assessment (HIA) to quantify health benefits for several PM and O3 air pollution reduction scenarios in the Mexico City Metropolitan Area (MCMA). Results from this HIA will contribute to the scientific support of the MCMA air quality management plan (PROAIRE) for the period 2011-2020. Materials and methods. The HIA methodology consisted of four steps: 1) selection of the air pollution reduction scenarios, 2) identification of the at-risk population and health outcomes for the 2005 baseline scenario, 3) selection of concentration-response functions and 4) estimation of health impacts. Results. Reductions of PM10 levels to 20 μg/m³ and O3 levels to 0.050ppm (98 µg/m³) would prevent 2300 and 400 annual deaths respectively. The greatest health impact was seen in the over-65 age group and in mortality due to cardiopulmonary and cardiovascular disease. Conclusion. Improved air quality in the MCMA could provide significant health benefits through focusing interventions by exposure zones.

Objetivo. Realizar una evaluación de impacto en salud (EIS) que documente los beneficios en salud ante diversos escenarios de reducción de PM10 y O3 en el aire de la Zona Metropolitana del Valle de México (ZMVM). Los resultados contribuyen al sustento científico del plan de gestión de calidad del aire (PROAIRE 2011-2020). Material y métodos. La metodología de EIS comprende cuatro pasos: 1) selección de los escenarios de reducción, 2) identificación de la población en riesgo y de los eventos en salud para el año basal 2005, 3) selección de las funciones de concentración-respuesta y 4) estimación del impacto en la salud. Resultados. Reducciones de PM10 a 20μg/m³ y de O3 a 0.050ppm (98 µg/m³) evitarían, respectivamente, cerca de 2 300 y 400 muertes por año. El mayor impacto se observa en el grupo de más de 65 años y en la mortalidad por causas cardiopulmonares y cardiovasculares. Conclusiones. Mejorar la calidad del aire en la ZMVM podría reflejar importantes beneficios para la salud focalizados por zonas o áreas de exposición.

Temporomandibular Disorders in a Sample Population of the Brazilian Northeast

Temporomandibular disorder (TMD) is a common condition. This study is part of a research group and it investigated the prevalence of TMD and myofascial pain and its association with gender, age and socioeconomic class. The sample comprised 100 subjects, aged 15 to 70, users of the Family Health Units' services, in the city of Recife, PE, Brazil. The TMD degree was evaluated using the Research Diagnostic Criteria for TMD and socioeconomic class by the Economic Classification Criteria Brazil. Categorical variables were analyzed by chi-square test for proportions and Fisher's exact test for 2x2 tables, and binary logistic analysis to track the relationship between the independent and dependent variables. According to the results, 42% of the subjects had TMD and 14% myofascial pain. No statistically significant association could be found between TMD and gender or socioeconomic class, but it was found to have statistically significant association with age, and myofascial pain was associated with socioeconomic class. Considering that the results of the present study should be confirmed by further studies and the fact that this was a pilot study, the prevalence must be analyzed with caution.

Disfunção temporomandibular (DTM) é uma condição comum. Este estudo é parte de um grupo de pesquisa e investigou a prevalência de DTM e dor miofascial e suas associações com sexo, idade e classe socioeconômica. A amostra foi composta por 100 indivíduos, com idades entre 15 e 70 anos, usuários das Unidades de Saúde da Família, na cidade de Recife, PE. O grau de DTM foi avaliado usando os Critérios de Diagnósticos Científicos em DTM, e classe socioeconômica com o Critério de Classificação Econômica Brasil. As variáveis categóricas foram analisadas pelo teste do qui-quadrado para proporções e teste exato de Fisher para tabelas 2x2, e a análise logística binária para traçar a relação entre as variáveis independentes e dependentes. De acordo com os resultados, 42% dos indivíduos tinham DTM e 14% dor miofascial. Não houve associação estatisticamente significativa entre DTM e sexo ou classe socioeconômica, mas houve associação estatisticamente significativa com a idade e a dor miofascial foi associada com a classe socioeconômica. Considerando-se que os resultados do presente estudo devam ser confirmados em outros estudos e por causa de sua natureza piloto, a prevalência deve ser analisada com cautela.

Alcohol-induced Hyperlipidemia Is Ameliorated by Orally Administered DWP208, a Sodium Succinate Form of ZYM201

DWP208 is a sodium succinate form of ZYM-201 which is a triterpenoid glycoside isolated from Sanguisorba officinalis, a medicinal plant prescribed for various diseases, such as duodenal ulcers and bleeding in East Asian counties. We demonstrated that this compound is able to normalize the altered lipid metabolism induced by hyperglycemia and a high fat diet. In this study, we determined whether hyperlipidemic conditions induced with chronically treated alcohol can also be restored by DWP208. Similar to our previous results, orally administered DWP208 (1 to 10 mg/kg) also ameliorated the hyperlipidemia that was induced by alcohol. This compound reversed the alcohol-induced hyperlipidemia including (i) up-regulated hyperlipidemic parameters such as low-density lipoprotein (LDL), very low-density lipoprotein (VLDL), atherosclerotic index (AI), triglyceride, and total cholesterol, and (ii) down-regulated hyperlipidemic parameters such as absolute body weight, superoxide dismutase (SOD) activity, and high-density lipoprotein (HDL) in serum and liver. According to our data, the ameliorative activity of DWP208 is due to its indirect anti-oxidative activity as a result of which lipid peroxide and hydroxyl radical levels were reduced and the activity of SOD was enhanced. Therefore, our data strongly suggest that DWP208 can be used as a remedy against alcohol-induced hyperlipidemia.

Metabolomics approach to serum biomarker for loperamide-induced constipation in SD rats / 한국실험동물학회지

Loperamide has long been known as an opioid-receptor agonist useful as a drug for treatment of diarrhea resulting from gastroenteritis or inflammatory bowel disease as well as to induce constipation. To determine and characterize putative biomarkers that can predict constipation induced by loperamide treatment, alteration of endogenous metabolites was measured in the serum of Sprague Dawley (SD) rats treated with loperamide for 3 days using 1H nuclear magnetic resonance (1H NMR) spectral data. The amounts and weights of stool and urine excretion were significantly lower in the loperamide-treated group than the No-treated group, while the thickness of the villus, crypt layer, and muscle layer was decreased in the transverse colon of the same group. The concentrations of aspartate aminotransferase (AST), lactate dehydrogenase (LDH) and creatinine (Cr) were also slightly changed in the loperamide-treated group, although most of the serum components were maintained at a constant level. Furthermore, pattern recognition of endogenous metabolites showed completely separate clustering of the serum analysis parameters between the No-treated group and loperamide-treated group. Among 35 endogenous metabolites, four amino acids (alanine, glutamate, glutamine and glycine) and six endogenous metabolites (acetate, glucose, glycerol, lactate, succinate and taurine) were dramatically decreased in loperamide-treated SD rats. These results provide the first data pertaining to metabolic changes in SD rats with loperamide-induced constipation. Additionally, these findings correlate the changes in 10 metabolites with constipation.

Metabolic shift of Corynebacterium acetoacidophilum-deltaldh under oxygen deprivation conditions / 生物工程学报

Lactate and succinate were produced by Corynebacterium acetoacidophilum from glucose under oxygen deprivation conditions. To construct knockout mutant, lactate dehydrogenase gene (ldh) of C. acetoacidophilum was deleted by double-crossover chromosome replacement with sacB gene. Comparing with the wild strain ATCC13870, ldhA-deficent mutant produced no lactate with glucose consumption rate decreased by 29.3%, while succinate and acetate concentrations were increased by 45.6% and 182%, respectively. Moreover, the NADH/NAD+ rate was less than 1 (about 0.7), and the activities of phosphoenolpyruvate carboxylase and acetate kinase of the ldhA-deficent mutant were enhanced by 84% and 12 times, respectively. Our studies show that succinicate and acetate production pathways are strengthened by blocking lactate synthesis. It also suggests that improving NADH supply and eliminating acetate generation are alternative strategies to get high succinate-producer.

NMR-based analysis of water soluble extracts of different Astragali Radix / 药学学报

Water soluble extract (WSE) is an important index for the quality evaluation of Astragali Radix (AR). In this study, the WSE of the wild AR from Shanxi province (SX) and the cultivated AR from Gansu Province (GS) were compared. The WSEs of two types of AR were determined according to the appendix of Chinese pharmacopoeia. Then the WSEs were subjected to NMR analysis, and the obtained data were analyzed using HCA, PCA, OPLS-DA, microarray analysis, and Spearman rank analysis. In addition, the Pearson correlation of differential metabolites were also calculated. The results showed that the WSE content of GS-AR (37.80%) was higher than that of SX-AR (32.13%). The main constituent of WSE was sucrose, and other 18 compounds, including amino acids, organic acids, were also detected. Multivariate analysis revealed that SX-AR contained more choline, succinic acid, citric acid, glutamate, taurine and aspartate, while GS samples contained more sucrose, arginine and fumaric acid. In addition, the Pearson correlations between different metabolites of the two types of AR also showed apparent differences. The results suggested that the WSE of two types of AR differs not only in the content, but also in the chemical compositions. Thus, the cultivation way is important to the quality of AR. This study supplied a new method for the comparison of extract of herbal drugs.

Microbiological Characteristics of Wild Yeast Strain Pichia anomala Y197-13 for Brewing Makgeolli

Makgeolli is a traditional cloudy-white Korean rice wine with an alcohol content of 6~7%. The present study investigated the morphological characteristics, carbon-utilizing ability, fatty acid composition, alcohol resistance, glucose tolerance, and flocculence of Saccharomyces cerevisiae Y98-5 and Pichia anomala Y197-13, non-S. cerevisiae isolated from Nuruk, which is used in brewing Makgeolli. Similar morphological characteristics were observed for both isolated wild yeast strains; and the carbon source assimilation of Y197-13 differed from that of other P. anomala strains. Strain Y197-13 was negative for D-trehalose, mannitol, arbutin, I-erythritol, and succinic acid. The major cellular fatty acids of strain Y197-13 included C18:2n6c (33.94%), C18:1n9c (26.97%) and C16:0 (20.57%). Strain Y197-13 was Crabtree-negative, with 60% cell viability at 12% (v/v) ethanol. The flocculation level of strain Y197-13 was 8.38%, resulting in its classification as a non-flocculent yeast.

Urine metabonomic study of intervention effects of Morinda officinalis how. on 'kidney-yang deficiency syndrome' / 药学学报

To investigate the intervention effects of Morinda officinalis How. on 'Kidney-yang deficiency syndrome' induced by hydrocortisone in rats, the metabolic profiles of rat urine were characterized using proton nuclear magnetic resonance and principal component analysis (PCA) was applied to study the trajectory of urinary metabolic phenotype of rats with 'Kidney-yang deficiency syndrome' under administration of M. officinalis at different time points. Meanwhile, the intervention effects of M. officinalis on urinary metabolic potential biomarkers associated with 'Kidney-yang deficiency syndrome' were also discussed. The experimental results showed that in accordance to the increased time of administration, an obvious tendency was observed that clustering of the treatment group moved gradually closed to that of the control group. Eight potential biomarkers including citrate, succinate, alpha-ketoglutarate, lactate, betaine, sarcosine, alanine and taurine were definitely up- or down-regulated. In conclusion, the effectiveness of M. oficinalis on 'Kidney-yang deficiency syndrome' is proved using the established metabonomic method and the regulated metabolic pathways involve energy metabolism, transmethylation and transportation of amine. Meanwhile, the administration of M. officinalis can alleviate the kidney impairment induced by 'Kidney-yang deficiency syndrome'.

Effect of overexpressing isocitrate lyase on succinate production in ldh(-1) Corynebacterium glutamicum / 生物工程学报

Corynebacterium glutamicum SA001 is a mutant with lactate dehydrogenase (ldhA) deletion. In order to increase metabolic flux from isocitrate to succinate, and to improve the production of succinate under anaerobic conditions,we transducted the gene aceA coding isocitrate lyase (ICL) from Escherichia coli K12 into Corynebacterium glutamicum SA001 (SA001/pXMJ19-aceA). After 12 h aerobic induction by adding 0.8 mmol/L of IPTG, the recombinant strain was transferred to anaerobic fermentation for 16 h. Succinate reached 14.84 g/L, with a productivity of 0.83 g/(L x h). Compared to C. glutamicum SA001, the activity of ICL of the recombinant strain was increased 5.8-fold, and the succinate productivity was increased 48%. Overexpression of isocitrate lyase will increase the metabolic flux of glyoxylate bypass flowing to succinate.

Mutating Escherichia coli by atmospheric and room temperature plasmas for succinic acid production from xylose / 生物工程学报

Escherichia coli AFP111 is a spontaneous mutant with mutations in the glucose specific phosphotransferase system (ptsG) in NZN111 (delta pflAB deltaldhA). In AFP111, conversion of xylose to succinic acid generates 1.67 molecule of ATP per xylose. However, the strain needs 2.67 molecule ATP for xylose metabolism. Therefore, AFP111 cannot use xylose due to insufficient ATP under anaerobic condition. Through an atmospheric and room temperature plasma (ARTP) jet, we got a mutant strain named DC111 that could use xylose under anaerobic condition in M9 medium to produce succinic acid. After 72 h, DC111 consumed 10.52 g/L xylose to produce 6.46 g/L succinic acid, and the yield was 0.78 mol/mol. Furthermore, the reaction catalyzed by the ATP-generating PEP-carboxykinase (PCK) was enhanced. The specific activity of PCK was 19.33-fold higher in DC111 than that in AFP111, which made the strain have enough ATP to converse xylose to succinic acid.

Succinic acid production with Escherichia coli AFP111 recovered from fermentation / 生物工程学报

During the anaerobic fermentation by Escherichia coli AFP111 for succinic acid production, the viable cell concentration and productivity were decreased with the raising of succinic acid concentration. In order to restore cellular succinic acid productivity and prolong fermentation time, we collected strains and refreshed medium for repetitive succinic acid production. However, productivity is lower than that in the anaerobic fermentation before reusing strains. To enhance the productivity, strains were aerobically cultivated for 3 h in pure water before anaerobic fermentation. The activities of key enzymes were enhanced for better performance in producing succinic acid at anaerobic stage. After three rounds of repetitive fermentations, succinic acid concentration and yield reached to 56.50 g/L and 90% respectively. The succinic acid productivity was 0.81 g/(L x h), which was 13% higher than the repetitive fermentations without aerobic activation of the strains.