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To acquire high-quality electrocardiogram (ECG) signals, traditional Ag/AgCl wet electrodes used together with conductive gel can effectively reduce electrode-skin interface impedance (EII) in a short term. However, their weaknesses of poor flexibility and instability can no longer meet the long-term monitoring requirements of intelligent wearable devices. Owing to the flexible dry electrode without conductive gel, it is a good choice to solve the critical problem on drying-out of conductive gel. Therefore, we develop a flexible microneedle array electrode (FMAE) based on polydimethylsiloxane (PDMS) substrate, which obtains reliable bioelectrical signals by way of penetrating into the stratum corneum (SC) of the skin. The fabrication process, including silicon mold, twice PDMS shape-transferring and encapsulation, has advantages of low cost, repeatable production and good biocompatibility. Afterwards, by comparing the performance with different electrodes, impedance test results indicate that the impedance of FMAE are smaller and more stable, and ECG tests in long term and at resting/jogging states also verify that FMAE can obtain durable, stable and reliable signals. In conclusion, FMAE is promising in long-term ECG monitoring.

In recent years, with the rapid development of the automotive industry, a large amount of electronic equipment was installed into the car. Due to the space constraints, lots of complex electromagnetic compatibility problems occur caused by the electromagnetic interference between different instruments. Therefore, for GPS navigation equipment installed inside the vehicle, a good electromagnetic compatibility and anti-jamming performance is significant. This paper describes the electromagnetic interference sources that affects the vehicle GPS navigation equipment, analysis the main interference propagation path, as well as this paper provides some of the optimization method to reduce the electromagnetic compatibility problems that may be encountered in the real work, which is critical for the safety and reliable operation of the GPS navigation equipment.

The objective of this research was to understand how the initial glucose concentration influences adenosine (AR) production and metabolic flux shift on the cultivation of Bacillus subtilis CGMCC 4484. Experiments confirmed that initial glucose concentration affects cell growth, AR production and metabolites, significantly. The flux distribution at the key nodes of glucose-6-phosphate (G6P), pyruvate (PYR) and acetyl coenzyme-A (AcCoA) could be affected by changing the glucose concentration. Based on kinetic analysis of specific rates, the low-glucose concentration was better for both cell growth and AR production during the first 12 h. However, the high-glucose concentration was more favorable for AR formation after 18 h. Furthermore, different simplified feeding strategies were designed to achieve higher AR accumulation. The final AR concentration of 15.60 g L(-1) was achieved when an optimized constant-feeding strategy was used, which was 21.02 % higher than batch fermentation. This was the first time to investigate the regulation of the glucose metabolism of AR-producing B. subtilis.

Removal of biobutanol from acetone-butanolethanol (ABE) fermentation broth can be achieved by fixed-bed sorption by means of KA-I resin, and the relevant breakthrough curves would provide much valuable information to help design a continuous fixed-bed sorption process in field application. In the present study, the effects of several important design parameters, i.e., initial butanol concentration (C f: 3.0 ∼ 30.0 g/L), inlet flow rate (Q f: 0.5 ∼ 5.5 mL/min) and adsorbent bed height (Z: 4.2 ∼ 18.0 cm), on the adsorption breakthrough curves of KA-I resin in a fixed-bed column were investigated. It was found that the amount of adsorbed butanol at breakthrough point was increased with an increase in the value of C f and Z; and with decrease in the value of Q f. However, the maximum sorption capacities of butanol at saturated point were basically unchanged. Three well-established fixed-bed adsorption models, namely Thomas, Yoon-Nelson and Adams-Bohart, were applied to predict the breakthrough curves and to determine the characteristic parameters of fixed-bed column, which are the basis for the process design at a real scale. Good agreement between the theoretical breakthrough curves and the experimental result were observed using Thomas and Yoon-Nelson models.

Adenylate cyclase (EC 4.6.1.1) catalyzes the formation of cyclic adenosine-3′,5′-monophosphate (cAMP) from adenosine 5′-triphosphate (ATP). Recombinant Escherichia coli overexpressing adenylate cyclase was used to synthesize cAMP by whole cell catalysis. Some key parameters were examined during the catalytic process, while pH and Mg2+ were found to influence cAMP production significantly. Optimum conditions were pH 8.52 and 30 °C with 77.2 mM Mg2+ in 100 mM Tris-HCl buffer, including 0.25% Triton-X 100 as detergent and 30 mM pyruvate sodium as enzyme activator for 6 h. 14.93 g/L of cAMP was produced with a conversion rate of 91.5%. The current work provided a potential way for the industrial production of cAMP.

Computational modeling is a useful approach for the characterization, development, and validation of desorption chromatography. Batch and dynamic desorption experimental results are helpful for the selection of an appropriate desorbent and the design of a desorption processes. In this study, we used an aqueous HCl solution ranging from 0.030 mol/L to 0.060 mol/L to desorb cAMP (adenosine 3′,5′-cyclic monophosphate) from a presaturated anion exchange resin (D-13). Good results were obtained in terms of the desorption rate and cAMP recovery. Subsequently, general rate model (GRM) that incorporated counter-ion flux was used to describe the desorption kinetics of the batch experiments. The superficial rate constant, K d , of the cAMP/HCl reaction on activated ion exchange sites inside the resin was estimated as 0.130 L/(mol/s) using the least squares fitting method, which was then applied for predicting the dynamic desorption processes. The pore diffusion coefficients for Cl − and cAMP were estimated as 1.57×10 −9 and 5.71×10 −10 m 2 /s, respectively. We verified the applicability of this GRM model to a column desorption process by experimentally investigating the effects of the HCl concentration, flow rate, and column aspect ratio on column desorption. The experimental results could be predicted successfully using the GRM model. The validated GRM may provide an important basis for future scale-up of the cAMP desorption process.

Most reductases which belong to the short chain dehydrogenase/reductase (SDR) superfamily require NAD (P) H for activity. Addition of this cofactor was still necessary for the production of ethyl (S)-4-chloro-3-hydroxybutanoate by Escherichia coli even when a cofactor regeneration system was constructed by co-expressing carbonyl reductase from Pichia stipitis (PsCRI) and glucose dehydrogenase from Bacillus megaterium (BmGDH). In an attempt to reduce dependence on the expensive cofactor, compounds directly or indirectly involved in NADP synthesis were added to the medium. Only glutamine and xylose enhanced the content of intracellular NADP (H) and the concentration of product. The concentration and yield of (S)-CHBE reached 730 mM and 48.7%, with 30 g/L of glutamine and 40 g/L of xylose, a 2.6-fold increase over the control without the addition of the two compounds.

A novel polar macroporous adsorption resin (AX-1) has been applied for separation of d -lactic acid (DLA) from aqueous solutions in a fixed-bed chromatographic column. The adsorption equilibrium and kinetics were investigated experimentally. A column model was subsequently established and validated by comparison of the simulation results to the experimental data obtained at different operating conditions in terms of feed flow rates and initial concentrations as well as bed heights. At the end of this work, the recycling studies were carried out. It was found that the saturated resin could be washed out DLA completely and repeated use by 353 K hot water. The results show that the AX-1 resin has a high adsorption capacity to DLA while no retention to sulfate ion. Based on this kind of resin, a green-production refining process could be established since only water is added in the entire separation process.

Computational and theoretical modeling has become an important tool for the characterization, development and validation of packed beds. Relevant breakthrough curves would provide much valuable information on designing a fixed bed adsorption process in field applications. In this study, the hydrodynamic properties involved in the Navier–Stokes flow equation, such as velocity, pressure and permeability, in a packed bed were investigated. A two dimensional (2D) model based on the convection/diffusion approach theory and the Nernst–Planck model was adopted to describe the breakthrough curves of adenosine 3′,5′-cyclic monophosphate (cAMP) adsorption onto a porous resin adsorbent, SD-13, from an aqueous solution. The relevant ordinary partial equations were solved in COMSOL Multiphysics Software friendly and efficiently. Column experiments were performed at different conditions to verify the model, and the results indicated that the model describes well the breakthrough curves. The behaviors of exchanged counter-ion (Cl − ) in cAMP adsorption experiments were also predicted well.

Microbial nuclease P1 from Penicllium citrinum was immobilized on macroporous absorbent resins: strong polar poly (styrene-co-DVB) resin (SPPSD), polymethacrylic ester resin and poly (styrene-co-DVB)-Br resin. The results showed that SPPSD was the best carrier. Three methods of glutaraldehyde cross-linking were used and simultaneous immobilization and cross-linking (CIS) was demonstrated to be the best method. The functional properties of immobilized nuclease P1 were studied and compared to those of the free enzyme. The highest enzyme activities of free and immobilized nuclease P1 were obtained in 0.2 M acetate buffer at pH 4.5 and a temperature of 70 °C. An increase in Km (from 3.165 to 18.125 mg mL−1) and a decrease in Vmax (from 1667.18 to 443.95 U min−1 mL−1) were recorded after immobilization. SPPSD-glutaraldehyde-nuclease P1 exhibited better thermal stability than the free enzyme. The apparent activation energy (Ea) of the free and immobilized nuclease P1 was 137.04 kJ mol−1 and 98.43 kJ mol−1, respectively, implying that the catalytic efficiency of the immobilized enzyme was restricted by mass-transfer rather than kinetic limit.

Experiments confirmed dissolved oxygen (DO) definitely affects cyclic adenosine monophosphate (cAMP) production by Arthrobacter A302. Production of cAMP by batch fermentation was investigated under various DO conditions. A two-stage DO control strategy was proposed to achieve optimal production of cAMP based on the kinetic analysis: the DO level was controlled at 40% during the first 18 h and then switched to 30%. Relatively high cAMP production (9.9 g L(-1)) was achieved by applying this strategy. The cAMP productivity (0.14 g L(-1) h(-1)) was also successfully improved by 85.1, 59.3, 15.1 and 28.0%, compared to cases in which DO was uncontrolled or DO levels were held at 20, 30 and 40%, respectively. This is the first report of the use of a two-stage DO control strategy in cAMP production, and it was verified to be an effective method for enhancing the cAMP yield via this strain.

The solubility of l -phenylalanine in water and binary mixtures (methanol + water and ethanol + water) at temperatures ranging from 288.15 to 318.15 K was investigated. The results obtained from these measurements were correlated with the temperature and the molar fraction of water by the combined nearly ideal binary solvent (CNIBS)/Redlich–Kister(R–K) model and the semiempirical Apelblat model. Both of the models demonstrated good fitting with the experimental data, while the CNIBS/R–K model gave a more accurate prediction. In addition, the thermodynamic properties of the solution process, including the Gibbs energy, enthalpy, and entropy, were obtained using the van’t Hoff equation and the Gibbs equation. The experimental results showed that water was a better solvent for l -phenylalanine than methanol and ethanol, which could thus be used as effective anti-solvents in the crystallization process. For all the cases studied, the values of both the standard molar enthalpy change and standard molar Gibbs energy change of solution were positive, which indicated that the process was endothermic and not spontaneous.

The cya gene encoding adenylate cyclase was cloned from Arthrobacter sp. CGMCC 3584 by thermal asymmetric interlaced PCR for the first time. It exhibited an open reading frame containing 1,125 bp and encoding 374 amino acids. Amino acid sequence analysis showed that this enzyme was a class III adenylate cyclase. Expression of the cya gene was carried out in Escherichia coli Rosetta, and purification was performed via Ni2+-NTA agarose gel column. SDS-PAGE indicated that the molecular mass of the recombinant adenylate cyclase was 45 kDa. The V max and K m were determined to be 5.06 μmol/min/mg and 7.56 mM, respectively. The optimum pH and temperature were 8.0 and 35 °C. Several divalent metal ions were found to activate the enzyme to different extents, and the maximal specific activity reached 3.04 μmol/min/mg when 50 mM Mg2+ was added. This was the first report of the cloning of an adenylate cyclase gene from Arthrobacter sp.

BACKGROUND: Owing to the rapid depletion of petroleum fuel, the production of bio-butanol has attracted much attention. However, low butanol productivity severely limits its potential industrial application. It is important to establish an approach for recovering low-concentration butanol from fermentation broth. Experiments were conducted using batch adsorption mode under different conditions of initial butanol concentration and temperature. Batch adsorption data were fitted to Langmuir and Freundlich isotherms and the macropore diffusion, pseudo-first- and second-order models for kinetic study. RESULTS: The maximum adsorption capacity of butanol onto KA-I resin increase with increasing temperature, ranged from 139.836 to 304.397 mg g−1. The equilibrium adsorption data were well fitted by the Langmuir isotherm. The adsorption kinetics was more accurately represented by the macropore diffusion model, which also clearly predicted the intraparticle distribution of the concentration. The effective pore diffusivity (Dp) was dependent upon temperature, but independent of initial butanol concentration, and was 0.251 × 10−10, 0.73 × 10−10, 1.32 × 10−10 and 4.31 × 10−10 m2 s−1 at 283.13, 293.13, 303.13 and 310.13 K, respectively. CONCLUSION: This work demonstrates that KA-I resin is an efficient adsorbent for the removal of butanol from aqueous solutions and available for practical applications for future in situ product recovery of butanol from ABE fermentation broth. Copyright © 2012 Society of Chemical Industry

A whole-cell biocatalytic process for uridine 5'-monophosphate (UMP) production from orotic acid by Saccharomyces cerevisiae was developed. To rationally redistribute the metabolic flux between glycolysis and pentose phosphate pathway, statistical methods were employed first to find out the critical factors in the process. NaH(2)PO(4), MgCl(2) and pH were found to be the important factors affecting UMP production significantly. The levels of these three factors required for the maximum production of UMP were determined: NaH(2)PO(4) 22.1 g/L; MgCl(2) 2.55 g/L; pH 8.15. An enhancement of UMP production from 6.12 to 8.13 g/L was achieved. A significant redistribution of metabolic fluxes was observed and the underlying mechanism was discussed.

The experiments were based on multivariate statistical concepts, and response surface methodology (RSM) was applied to optimize the fermentation medium for the production of ribonucleic acid (RNA) by Candida tropicalis no. 121. The process involved the individual adjustment and optimization of various medium components at shake flask level. The two-level Plackett-Burman (PB) design was used to screen the medium components, which significantly influenced RNA production. Among seven variables, the concentrations of molasses, ZnSO4, and H3PO4 were found to be the important factors that significantly affected RNA production (confidence levels above 95%). These factors were further optimized using a central composite design (CCD) and RSM. The optimum values for the critical components were as follows: molasses 47.21 g/L: ZnSO4 0.048 g/L; H3PO4 1.19 g/L. Under optimal conditions, RNA production was 2.56 g/L, which was in excellent agreement with the predicted value (2.561 g/L), and led to a 2.1-fold increase compare with that using the original medium in RNA production.

The adsorption behavior of uridine 5′-monophosphate (UMP) on a gel-type anion-exchange resin SD3 at different temperatures was investigated by the batch method. The dissociation equilibrium of UMP ...

A glucose utilizing strain, Arthrobacter A302 was used for cyclic adenosine monophosphate (cAMP) production in batch modes. The non-structured model in a 5 l stirred tank bioreactor for understanding, controlling, and optimizing the fermentation process was proposed using the logistic equation for microbial growth, the Luedeking-Piret equation for product formation and Luedeking-Piret-like equation for substrate uptake, respectively. The production of cAMP was a mixed-growth-associated pattern. Based on model prediction, a comparison of calculated value using the parameters evaluated above with another experimental data in 30 l bioreactor was used to test the model. The results predicted from the model were in good agreement with the experimental observations in 30 l bioreactor, which demonstrated that the model might be useful for the development and optimization of production of cAMP in industrial scale. Based on estimated kinetic parameters, three different fed-batch modes, constant rate and intermittent (once and repeated), were adopted in order to obtain more cAMP accumulation. Furthermore, the final production of cAMP reached 11.24 g l−1 after 72 h incubation using three stages feeding strategy. In particular, the cAMP productivity (0.156 g l−1 h−1) was successfully improved by 22.83, 11.43 and 9.86%, respectively, compared with the modes of the batch, constant rate fed-batch and intermittent fed-batch once.

The mutant strain designated as N409 was obtained with a high yield of nuclease p1. The activity of nuclease p1 was 421 U/mL from the mutant strain N409, which was increased by 86% compared with the control. The fermentation kinetics of nuclease p1 by the mutant strain N409 was studied in a 30 L external airlifting bioreactor. A model was proposed using the logistic equation for microbial growth, the Luedeking-Piret equation for product formation and a Luedeking-Piret-like equation for substrate uptake. The results predicted from the model were in good agreement with the experimental observations.

The molecular structure of cytidine 5′-diphosphocholine sodium (CDPC) grown from a mixture of ethanol and water was determined by X-ray diffraction (XRD). CDPC was found to have an orthorhombic structure with confirmed lattice parameters of a = 6.978 A, b = 12.406 A and c = 29.326 A. This nucleotide coenzyme was highly folded and net-like. Each crystallographic unit consisted of one sodium atom, one pyrophosphate group, one cytosine group, one coordinated water molecule, one pentose molecule, and three lattice water molecules. The interspaces of neighboring CDPC molecules were filled with water molecules and methyl groups. Although the coordinated water was connected to sodium atoms, the lattice water molecules formed chair-shaped water hexamers. The hydrogen bonds which played an important role in maintaining the structure included O H···O, N H···O and C H···O and ranged in length from 2.682 (17) to 3.349 (17) A. Fourier transform infrared spectroscopy (FTIR) showed a broad absorption in the 400–2000 cm−1 region characteristic of short hydrogen bonds. So for industrial crystallization, methods which could eliminate the influence of hydrogen bonds should be taken, and it would be beneficial for the process of crystallization.

In a batch equilibrium system, the maximum adsorption capacity of cAMP onto an anion-exchange resin reached 0.1718, 0.1956, 0.2764 and 0.3437 g g −1 at 283, 293, 303 and 313 K, respectively. The adsorption data obtained were well described by the Langmuir isotherm. In the batch kinetic system, Fick diffusion, pseudo first-order and pseudo second-order models were applied to simulate the experimental kinetic data. The results revealed that the Fick model best described the adsorption process, and clearly predicted the intraparticle distribution of the concentration. The effective diffusion coefficients ( D e ) for 283, 293, 303 and 313 K were 0.37 × 10 −10 , 0.51 × 10 −10 , 0.86 × 10 −10 and 1.41 × 10 −10 m 2 s −1 , respectively. The thermodynamic parameters such as Δ G 0 , which were all negative, indicated that the adsorption of cAMP onto the anion-exchange resin was spontaneous and the positive value of Δ H 0 (+8.66 kJ mol −1 ) showed that the adsorption was an endothermic reaction.

Statistical experimental designs were used to optimize the composition of culture media for the production of D-ribose by Bacillus subtilis. A fractional factorial design 2 (5-2) was used to determine medium components that sig- nificantly affected D-ribose production. The concentrations of glucose and (NH4)2SO4 were the significant factors. Cen- tral composite design and response surface methodology were then used to estimate the quadratic response surface and determine the factor levels for maximum production of D-ribose. Finally, the optimal medium composition was obtained (g/L): glucose, 172.75; (NH4) 2SO4, 13.2; yeast powder, 4; corn steep liquor, 8 and MnSO4, 0.5. This optimization strategy increased D-ribose production from 73.21 g/L to 88.57 g/L, an increase of 22% compared with the original conditions. The D-ribose production yield to glucose concentration was also enhanced from 0.37 g/g to 0.52 g/g. Con- firmatory experiments were also performed to demonstrate the accuracy of the model. Under the optimal medium using ammonia to control pH in a 5 L fermenter, the D-ribose yield was increased to 95.28 g/L after 3 days of cultivation at 37 o C.

To obtain a cyclic adenosine monophosphate (cAMP) high-yield production strain, Arthrobacter NG-1 was mutated by N + ion implantation with an energy level of 10 keV and dose of 7×10 15 ions/cm 2 . Combined with directed screening methods, a xanthine-defective and 8-azaguanine (8-AG)-resistant mutant Arthrobacter A302 was selected. The concentration of cAMP produced by this mutant was 41.7% higher than that of the original strain and reached 9.78 g/L. Through ten-generation investigation, the capability of cAMP production of A302 was found to be stable. Compared with the original strain, the special activities of key enzymes in A302, which influenced the cAMP biosynthesis, was analyzed. IMP dehydrogenase activity was defective, whereas PRPP amidotransferase, sAMP synthetase and adenylate cyclase activities were increased by 61.5%, 147% and 21.7%, respecitively, which might explain the mutagenesis mechanism by N + ions implantation under the enzymatic level.

A whole cell biocatalytic process for uridine 5'-monophosphate (UMP) production from orotic acid by Saccharomyces cerevisiae was developed. The concentration of UMP was increased by 23% when 1 g l(-1) sodium citrate was fed into the broth. Effects of citrate addition on UMP production were investigated. Glucose-6-phosphate pool was elevated by onefold, while FBP and pyruvate were decreased by 42% and 40%, respectively. Organic acid pools such as acetate and succinate were averagely decreased by 30% and 49%. The results demonstrated that manipulation of citrate levels could be used as a novel tool to regulate the metabolic fluxes distribution among glycolysis, pentose phosphate pathway, and TCA cycle.

An improved, simple gas chromatography –flame ionization detection (GC–FID) method was developed for measuring the products of acetone-butanol-ethanol (ABE) fermentation and the combined fermentation/separation processes. The analysis time per sample was reduced to less than 10 min compared to those of a conventional GC–FID (more than 20 min). The behavior of the compounds in temperature-programmed gas chromatographic runs was predicted using thermodynamic parameters derived from isothermal runs. The optimum temperature programming condition was achieved when the resolution for each peak met the analytical requirement and the analysis time was shortest. With the exception of acetic acid, the detection limits of the presented method for various products were below 10 mg/L. The repeatability and intermediate precision of the method were less than 10% (relative standard deviation). Validation and quantification results demonstrated that this method is a sensitive, reliable and fast alternative for conventional investigation of the adsorption-coupled ABE fermentation process.

Simultaneous determination of organic acids using ion-exclusion liquid chromatography and ultraviolet detection is described. The chromatographic conditions are optimized when an Aminex HPX-87H column (300 × 7.8 mm) is employed, with a solution of 3 mmol/L sulfuric acid as eluent, a flow rate of 0.4 mL/min and a column temperature of 60°C. Eight organic acids (including orotic acid, α-ketoglutaric acid, citric acid, pyruvic acid, malic acid, succinic acid, lactic acid and acetic acid) and one nucleotide are successfully quantified. The calibration curves for these analytes are linear, with correlation coefficients exceeding 0.999. The average recovery of organic acids is in the range of 97.6% ∼ 103.1%, and the relative standard deviation is in the range of 0.037% ∼ 0.38%. The method is subsequently applied to obtain organic acid profiles of uridine 5'-monophosphate culture broth fermented from orotic acid by Saccharomyces cerevisiae. These data demonstrate the quantitative accuracy for nucleotide fermentation mixtures, and suggest that the method may also be applicable to other biological samples.

The traditional distillation method for recovery of butanol from fermentation broth is an energy-intensive process. Separation of butanol based on adsorption methodology has advantages in terms of biocompatibility and stability, as well as economy, and therefore gains much attention. However, the application of the commercial adsorbents in the integrated acetone-butanol-ethanol (ABE) fermentation process is restricted due to the low recovery (less than 85%) and the weak capability of enrichment in the eluent (3-4 times). In this study, we investigated the sorption properties of butanol onto three kinds of adsorbents with different polarities developed in our laboratory, that is, XD-41, H-511, and KA-I resin. The sorption behaviors of single component and ABE ternary mixtures presented in the fermentation broths on KA-I resin were investigated. KA-I resin had higher affinity for butanol than for acetone, ethanol, glucose, acetic acid, and butyric acid. Multicomponent ABE sorption on KA-I resin was modeled using a single site extended Langmuir isotherm model. In a desorption study, all the adsorbed components were desorbed in one bed volume of methanol, and the recovery of butanol from KA-I resin was 99.7%. The concentration of butanol in the eluent was increased by a factor of 6.13. In addition, KA-I resin was successfully regenerated by two bed volumes of water. Because of its quick sorption, high sorption capacity, low cost, and ease of desorption and regeneration, KA-I resin exhibits good potential for compatibility with future ABE fermentation coupled with in situ recovery product removal techniques.

Exogenous addition of a low concentration of acetate (2 g/L sodium acetate) effectively decreased acetic acid excretion and lowered the ATP content in Sporolactobacillus sp. Y2-8 without any growth defect although the acetate could not be utilized at an initial glucose concentration of 150 g/L. This induced an enhanced glycolytic flux with increased specific activities of hexokinase and phosphofructokinase, probably to compensate for the lowered efficiency of ATP production. However, with increasing concentrations (5 g/L sodium acetate), acetate was utilized first before being produced again, causing a growth lag at the transition. Glucose consumption was also reduced at high acetate concentrations, resulting in decreased d-lactic acid production. These results demonstrate that acetate plays a significant role in regulating glycolysis and growth of Sporolactobacillus.

During ribonucleic acid fermentation, the fermentative processes were researched at pH controlled at 4.0 and under natural conditions. Unstructured models in a 50-L airlift fermentor were established for batch RNA production at pH 4.0 using the Verhulst equation for microbial growth, the Luedeking-Piret equation for product formation and a Luedeking-Piret-like equation for substrate uptake. Parameters of the kinetic models were determined using origin 7.5. Based on the models estimated above, another batch fermentation experiment was conducted in a 300-L airlift fermentor, which demonstrated that the models could be useful for RNA production on an industrial scale. Additionally, continuous fermentation based on kinetic models was proposed to make full use of substrates and reduce the cost of waste water treatment. As a result, although the DCW and RNA concentration were 11.5 and 1.68 g L(-1), which were lower than that of batch fermentation, the sugar utilization increased by 14.3%, while the waste water decreased by more than 90%.

The production of cyclic adenosine monophosphate (cAMP) by Arthrobacter sp. A302 was studied in a 5 L stirred tank fermentor under a range of pH values (6.5-8.0) and glucose feeding rates. In batch fermentation under a controlled pH, the optimum pH for cell growth was 7.5 with dry cell density (X) of 11.43 g L, and the optimum pH for cAMP accumulation was 7.0 with cAMP concentration of 7.41 g L. In order to achieve the high X and cAMP yield simultaneously, a pH-shift control strategy was proposed based on kinetic analysis of specific cell growth rate (μ) and specific cAMP formation rate (q ( s )). In this method, pH was controlled to 7.0 for the first 30 h of fermentation, and then subsequently shifted to 7.5 and maintained until the end of the process. Application of this approach significantly enhanced the cAMP concentration. Thereafter, cAMP production was further improved by combining the above-mentioned pH-control system and fed-batch process with glucose at a constant feeding rate of 1.0 g L(-1 )h(-1). Under optimum conditions, the final cAMP production was 10.87 g L, which is 110.0, 46.7, and 27.7% higher than that of the pH-uncontrolled, pH-controlled, and pH-shift controlled methods, respectively.

Cyclic adenosine monophosphate (cAMP) was synthesized through the purine salvage synthesis pathway by Arthrobacter A302. Results showed that hypoxanthine was the best of the precursors, and the cAMP concentration reached 4.06 g/L. For inhibition of the glycolytic pathway, sodium fluoride was found the optimal effector, which was further studied on cAMP production. With the addition of 0.4 g/L of sodium fluoride, the maximal cAMP concentration reached 11.04 g/L, and the concentrations of lactic acid, alpha-ketoglutarate and citric acid were decreased by 77%, 86% and 76%, respectively. Meanwhile, the specific activities of glyceraldehyde 3-phosphate dehydrogenase, phosphofructokinase and pyruvate kinase were decreased by 66%, 61%, and 46%, respectively. By contrast the activity of 6-phosphoglucose dehydrogenase was increased by 100%, which demonstrated the redistribution of metabolic flux. This is the first study to reveal the regulatory mechanisms of different effectors on cAMP production among the EMP pathway, HMP pathway and TCA cycle.

Uridine diphosphate N-acetylglucosamine (UDPAG) can be produced by chemical, enzymatic, chemoenzymatic, and fermentative methods. In this study, we used whole-cell catalysis method to produce UDPAG for the first time by Saccharomyces cerevisiae. In order to increase the ATP utilization efficiency and UDPAG conversion yield, the response surface methodology was applied to optimize the whole-cell catalytic conditions for UDPAG production. Firstly, effects of uridine 5'-monophosphate (5'-UMP), glucosamine, vitamin B1, glycerol, magnesium chloride, potassium chloride, temperature, sodium dihydrogen phosphate, sodium acetate, fructose, and pH on UDPAG production were evaluated by a fractional factorial design. Results showed that UDPAG production was mainly affected by sodium dihydrogen phosphate, temperature, and vitamin B1. Then, the concentrations of sodium dihydrogen phosphate and vitamin B1 and temperature were further investigated with a central composite design and response surface analysis. The cultivation conditions to obtain the optimal UDPAG production were determined: sodium dihydrogen phosphate, 31.2 g/L; temperature, 29 degrees C, and vitamin B1, 0.026 g/L. This optimization strategy led to an enhancement of UDPAG production from 2.51 to 4.25 g/L, yield from 44.6% to 75.6% based on the initial 5'-UMP concentration, and ATP utilization efficiency from 7.43% to 12.6%.

Both stimulation of ammonium ion on the glycolytic flux and regulation by glycerol of enzymes in Kennedy pathway for cytidine diphosphate choline production in S. cerevisiae were studied. The conventional transformation course featured four stages. Firstly, CMP and choline chloride were phosphorylated and CDP-choline was formed rapidly; secondly, the rate of CDP-choline formation declined and CMP was not detected in the mixture; thirdly, CMP was released and the CDP-choline concentration reached a peak; Fourthly, the compound concentrations did not practically changes eventually. Using the central composite design, the concentration, yield, and utilization efficiency of energy reached 24.7 mmol/L, 82.3% and 10.6%, with 30 mmol/L of ammonium ion and 1% (V/V) of glycerol, respectively. Ammonium ion not only strengthened the glycolytic pathway, but also coordinated the reaction rate between the glycolytic pathway and the Kennedy pathway. Glycerol alleviated the activity decrease of the key enzymes in the mixture.

Response surface methodology was employed to optimize medium composition for the production of cyclic adenosine 3',5'-monophosphate (cAMP) with Microbacterium sp. no. 205. A fractional factorial design (2(11-7)) was applied to evaluate the effects of different components in the medium. K(2)HPO(4), MgSO(4) and NaF were found to significantly influence on the cAMP production. The steepest ascent method was used to access the optimal region of the medium composition. The concentrations of the three factors were optimized subsequently using central composite design and response surface methodology. The optimal medium composition to achieve the optimal cAMP production was determined (g/L): K(2)HPO(4), 12.78; MgSO(4), 3.53 and NaF, 0.18. The corresponding cAMP concentration was 8.50 g/L, which was about 1.8-fold increase compared with that using the original medium. Validation experiments were also carried out to prove the adequacy and the accuracy of the model obtained. The cAMP fermentation in 5L fermenter reached 9.87 g/L.