运用试验设计方法提高胞外杂合b-葡聚糖酶在重组大肠杆菌中的表达

A genetically engineered Escherichia coli JM109 harboring pLF3 was used to produce a hybrid extracellular β-glucanase. Starting with enzyme production medium, glycerol and yeast extract combined with NaNO3 were screened to be the most suitable carbon and nitrogen source, respectively. Analysis of six components of the enzyme production medium by employing statistical optimization methods such as Plackett-Burman design and steepest ascent showed that yeast extract was the only significant variable and its best concentration for enzyme production was 12g·L^-1. After optimization of the medium, 297.71U·ml^-1 of β-glucanase activity in the medium and 352350U·g^-1 of β-glucanase selectivity could be obtained, which were 14 and 72 folds higher than those obtained from original medium, respectively. Even higher enzyme activities were achieved by batch cultivations in a conventional stirred bioreactor on the optimized medium.     

运用试验读者设计方法提高胞外杂合β-葡聚糖酶在重组大肠杆菌中的表达

A genetically engineered Escherichia coli JM109 harboring pLF3 was used to produce a hybrid extracellular β-glucanase. Starting with enzyme production medium, glycerol and yeast extract combined with NaNO3 were screened to be the most suitable carbon and nitrogen source, respectively. Analysis of six components of the enzyme production medium by employing statistical optimization methods such as Plackett-Burman design and steepest ascent showed that yeast extract was the only significant variable and its best concentration for enzyme production was 12g·L-1. After optimization of the medium, 297.71U·ml-1 of β-glucanase activity in the medium and 352350U·g-1 of β-glucanase selectivity could be obtained, which were 14 and 72 folds higher than those obtained from original medium, respectively. Even higher enzyme activities were achieved by batch cultivations in a conventional stirred bioreactor on the optimized medium.     

原位氮饥饿发酵工艺中梯度补氮对谷氨酰胺合成酶的调控

The effects of uniform and gradient fed nitrogen on glutamine synthetase (GS), glutamate dehydrogenase(GDH) and glutamate synthase ((K)GAT)were investigated in glutamine production by fermentation of Corynebacterium glutamicum NS611 after 3 h of in-situ nitrogen starvation. It was shown that the strain in the later growth phase entered naturally into in-situ nitrogen starvation by controlling the initial concentration of urea and the biomass was slightly decreased. The pH value reached 6.5 again in the culture system, which confirmed the beginning of nitrogen starvation in the culture system. After 3 h nitrogen starvation the activity of GS was increased over two folds and the time of high activity of GS persisted three folds longer in the gradient fed nitrogen system than that in the normal fed batch. The higher activity of GDH was also maintained. The glutamine production increased by 72 % than the original technology of nitrogen starvation and the time of fermentation was shortened by above 12 h.     

添加剂EDTA对氢氧化镁反应结晶过程的影响(英文)

The effects of additive ethylenediaminetetraacetic acid (EDTA) on crystallization process were investigated by the induc-tion time of MgSO4-NaOH system. Nucleation and growth rates, growth mechanism and particle size distribution of magne-sium hydroxide precipitation were involved with. The induction time in unseeded and seeded precipitation of magnesium hydroxide with and without additive EDTA was measured. The conductivity method was used to determine the induction period. Theoretical relations of the induction time and supersaturation ratio for different growth mechanisms and a combined analysis on the induction time were applied to determine nucleation and growth rates. The growth mechanism of magnesium hydroxide precipitation was dis-closed by analyzing the experimental data with and without additive. The analysis on induction time indicated that additive EDTA had a significant influence on both nucleation and growth of magnesium hydroxide precipitation. The mechanism underlying the effect of EDTA on crystal growth was 2-dimension nucleation-mediated growth model.     

废轮胎二氧化碳活化借助析因设计的系统分析(英文)

In this study,waste tire was used as raw material for the production of activated carbons through pyrolysis.Tire char was first produced by carbonization at 550℃ under nitrogen.A two factorial design was used to optimize the production of activated carbon from tire char.The effects of several factors controlling the activation process,such as temperature(850-950 ℃),time(2-6 h) and percentage of carbon dioxide(70%-100%) were investigated.The production was described mathematically as a function of these three factors.First order modeling equations were developed for surface area,yield and mesopore volume.It was concluded that the yield,BET surface area and mesopore volume of activated carbon were most sensitive to activation temperature and time while percentage of carbon dioxide in the activation gas was a less significant factor.     

The development of Fructus corni quality standard considering the effects of processing

The quality standards for Fructus Comi have been established based on the effects of the manufacturing processes.Three critical process parameters(CPPs) of extraction,filtration,and concentration to prepare Fructus Comi concentrate were identified by Plackett-Burman design with a single batch of Fructus Corni,which were heating medium temperature,extraction time,and water addition.Morroniside yield,loganin yield,and dry matter yield were process critical quality attributes(CQAs).CPPs arranged with a Box-Behnken design were applied to treat different batches of Fructus Comi After constructing a model that included CPPs,material propertie s,and process CQAs,loganin content was found to be the critical material attribute(CMA).The design space was calculated with a probability method.According to the limits of process CQAs,the minimum content of loganin in Fructus Corni was calculated with an error propagation method,which was 6.92 mg·g~(-1).When the content of loganin in Fructus Corni reaches up to 6.92 mg·g~(-1), the material is considered high-quality and is most suitable for the process.High-quality material can be used for production of Fructus Comi concentrate.This method can also be used to set material quality standards for other Chinese medicines.     

累托石吸附分离水中金霉素(英文)

The removal of antibiotics from water by clay minerals has become the focus of research due to their strong adsorptive ability. In this study, adsorption of chlortetracycline (CTC) onto rectories was conducted and the effects of time, concentration, temperature and pH were investigated. Experimental results showed that adsorption equilibrium was reached in 8 h. Based on the Langmuir model, the maximum adsorption capacity of CTC on rectories was 177.7 mg·g 1 at room temperature. By the study on adsorption dynamics, it is found that the kinetic date fit the pseudo-second-order model well. The adsorption of CTC by rectories is endothermic and the free energy is in the range of 10 to 30 kJ·mol 1 . The pH value of solution has significant effects on adsorption and the optimal pH is at acidity (pH 2-6). At concentration of 2500 mg·L 1 , the intercalated CTC produces an interlayer space with a height of 1.38 nm, which is 1.12 nm in raw rectories, suggesting that the adsorption occurs between layers of rectories.     

Production of biodiesel from palm fatty acid distillate using sulfonated-glucose solid acid catalyst:Characterization and optimization

A palm fatty acid distillate (PFAD) has been used for biodiesel production. An efficient sulfonated-glucose acid catalyst (SGAC) was prepared by sulfonation to catalyze the esterification reaction. The effect of three variables i.e. methanol-to-PFAD molar ratio, catalyst amount and reaction time, on the yield of PFAD esters was studied by the response surface methodology (RSM). The optimum reaction conditions were:12.2:1 methanol-to-PFAD molar ratio, 2.9%catalyst concentration and 134 min of time as predicted by the RSM. The reaction under the optimum conditions resulted in 94.5%of the free fatty acid (FFA) conversion with 92.4%of the FAME yield. The properties of the PFAD esters were determined according to biodiesel standards.     

Anaerobic hydrogen production of molasses from mixed microbial communities immobilized by activated granular carbon

Molasses wastewater was evaluated as substrate for biohydrogen production by anaerobic fermentation in a novel continuous mixed attached growth reactor ( CMAGR ) with aeration pretreated sludge attached onto granular activated carbon under continuous flow condition.It was indicated that the CMAGR system was operated at the conditions of influent COD of 2000～6000mg / L , hydraulic retention time ( HRT ) of 6hand temperature of 35 ℃ , when the pH value and oxidation-reduction potential ( ORP ) ranged from 4.16and-434 mV respectively , stable ethanol-type fermentation was formed with the sum of ethanol and acetate concentration ratio of 89.3%to the total liquid products after 40days operation.The H 2 content in biogas and chemical oxygen demand ( COD ) removal were estimated to be 46.6% and 13% , respectively.It was also investigated that the effects of organic loading rates ( OLRs ) on CMAGR hydrogen production system.It was found that hydrogen production yield increased from 3.72 mmol / hL to 12.51 mmol / hL as OLRs increased from 8 kg / m 3 d to 32 kg / m 3 d.The maximum hydrogen production rate of 12.51mmol / hL at a OLR of 32kg / m 3 d and the maximum hydrogen yield by substrate consumed was 130.57 mmol / mol happened at OLR of 16 kg / m 3 d.Greater pHs appeared to be favour to butyrate production and the maximum of 0.51mol / mol was obtained at pH of 4.14.However , ethanol / acetate ratio was greater than 1.1at pH fluctuated between 3.4 - 3.6and 4.1 - 4.4which indicated that these pHs were favour to ethanol type fermentation.Therefore , the continuous mixed attached growth reactor ( CMAGR ) could be a promising attached growth system for biohydrogen fermentation.     

补料分批培养耐乙酸大肠杆菌生产人表皮生长因子

An acetate-tolerant mutant of Escherichia coli DH5α, DA19, was used for secretory production of human epidermal growth factor （hEGF） whose expression was under the control of phoA promoter. The recombinant cells were cultured in a chemically defined medium, and glucose was added at different specific provision rates during the growth and expression phases. It was found that pH had a significant effect on the extracellular hEGF production. The extracellular hEGF concentration was 75.5mg·L^-1, 5.2-fold of the level reached at pH 7.0, even though more acetate was produced. Nitrogen source was limited in the later growth phase. Supplementation of ammonium promoted the consumption of phosphate and reduced the time to exhaust phosphate, but the extracellular hEGF production was similar to that without supplementation of ammonium.     

ENZYME-MEDIATED PRODUCTION OF SUGARS FROM SAGO STARCH: STATISTICAL PROCESS OPTIMIZATION

Glucoamylase (γ-amylase, EC 3.2.1.3) from Aspergillus niger was used to hydrolyze the soluble sago starch to reducing sugars without any major pretreatment of the substrate. A 2 L stirred tank reactor was used for the hydrolysis. The effects of pH, temperature, agitation speed, substrate concentration, and enzyme concentration on the reaction were investigated in order to maximize both the initial reaction velocity v and the final product yield Y_p/s. A response surface methodology central composite design was used for the optimization. A maximum Y_p/s of 0.58 g · g^?1 and a high v of 0.50 mmoles · L^?1 · min^?1 were predicted by the response surface at the identified optimal conditions (61°C, a substrate concentration of 0.1% (w/v, g/100 mL), an enzyme concentration of 0.2 U · mL^?1). The pH and agitation speed did not significantly affect the production of sugars. The subsequent validation experiments under the above-specified optimal conditions confirmed a maximum conversion rate and yield combination of 0.51 ± 0.07 mmoles · L^?1 · min^?1 and 0.60 ± 0.08 g · g^?1.     

Statistical optimization of fermentation conditions for the improved production of poly-β-hydroxybutyrate from Bacillus subtilis

Poly-β-hydroxybutyrate (PHB) has been an effective biodegradable plastic obtained by microbial fermentation. Batch fermentation of Bacillus subtilis features an attractive system for the production of PHB. Identification of appropriate media components and cultivation conditions are extremely important for the optimal production of biomass and/or PHB production. Statistical media design was utilized for the optimization of different fermentation variables (glucose, peptone, sodium chloride, K₂HPO₄, KH₂PO₄, ammonium sulfate, ammonium chloride, sodium sulfate, temperature, inoculum size, and pH). The optimized media predicted the optimal dry cell weight of 7.54?g?L^?1 and PHB production of 77.2?mg?L^?1 at 1?g?L^?1 of peptone, 1.46?g?L^?1 sodium sulfate, and pH 6.8 in 24?h. Glucose utilization, batch growth, and PHB production kinetics of B. subtilis were determined experimentally. The effect of substrate inhibition on specific growth rate was also determined experimentally for B. subtilis. The values of kinetic and substrate inhibition parameters obtained from this study shall be utilized to develop a mathematical model for PHB production for further improving the production of PHB.     

Selective Competitive Biosorption of Au(III) and Cu(II) in Binary Systems by Magnetospirillum gryphiswaldense

The biosorption of Au(III) and Cu(II) ions in both single and binary systems by Magnetospirillum gryphiswaldense (MSR-1) was investigated. For comparison with the selective reinforced competitive biosorption process in a binary system, the experimental research first explored the biosorption of Au(III) and Cu(II) in a single system under various conditions. The biomass exhibited the highest single Au(III) and Cu(II) ion adsorption yields at room temperature (25°C), pH values of 2.5 and 5.0, respectively, and a biomass concentration of 10 g · L^?1 (3.83 g · L^?1, dry basis). The experimental data from the single component system for the two metallic ions fitted well to a Langmuir isotherm and a pseudo second-order kinetic models. In the Au(III)-Cu(II) binary system, the coexistence of Cu(II) cations promoted the adsorption of Au(III) within a certain range of ratios. A new sigmoidal Cu(II) biosorption isotherm was determined specifically to reveal the Cu(II) adsorption behavior in this case.     

响应面法优化甘露醇产丁醇的发酵条件

以褐藻的主要成分甘露醇为底物,利用丙酮丁醇梭菌ATCC824发酵生产丁醇。采用Plackett-Burman（P-B）和Box-Behnken优化发酵条件。在Plackett-Burman实验设计时,考察牛肉膏、酵母浸粉、胰蛋白胨、乙酸铵、 KH2PO4、MgSO4?7H2O、FeSO4?7H2O、接种量、发酵温度、初始pH值这10个因素对丁醇产量影响,筛选出影响丁醇发酵的重要参数是发酵温度、初始pH值、乙酸铵浓度,利用Box-Behnken设计确定最优发酵条件为发酵温度37.3 ℃、初始pH值6.38、乙酸铵浓度2.82 g/L。数学模型分析预测最大丁醇产量为8.47 g/L。经实验验证表明,在优化条件下的丁醇产量平均值达到8.52±0.55 g/L。这说明利用统计学方法优化甘露醇的丁醇发酵条件是有效的。     

Application of Doehlert experimental design for the optimization of cadmium biosorption in an aqueous solution by marine yeast biomass of Yarrowia lipolytica

A cadmium biosorption process was optimized by varying three independent variables pH (4.5–7.5), initial cadmium ion concentration (10–30 mg L^?1), and Yarrowia lipolytica dosage (3–5 g L^?1) by using a Doehlert experimental design (DD) involving response surface methodology (RSM). For the maximum biosorption of cadmium ion in an aqueous solution by Y. lipolytica, a total of fifteen experimental runs were set and the experimental data fitted to the empirical second-order polynomial model of a suitable degree. The analysis of variance of the quadratic model demonstrates that the model was highly significant. Three-dimensional plots demonstrate relationships between the cadmium ion uptake with the paired variables (when other variable was kept at its optimal level), describing the behavior of biosorption system in a batch process. The model showed that cadmium uptake in aqueous solution was affected by all the three variables studied. The optimum values of the variables were found to be 6.43, 17.56 mg L^?1 and 3.63 g L^?1 for pH, initial cadmium ion concentration and biomass dosage, respectively, at a contact time of 40 min. At these optimal conditions, the maximum percentage biosorption of cadmium was predicted to be 48.89. The experimental values were in good agreement with predicted values and the correlation coefficient was found to be 0.9985. It showed that both monolayer adsorption and intra-particle diffusion mechanisms were effective in the cadmium biosorption process. Therefore, it is apparent that the DD involving RSM not only gives valuable information on interactions between the variables but also leads to identification of feasible optimum values of the studied variables.     

重组柠檬酸杆菌合成紫色杆菌素的工艺条件优化

以L-色氨酸为前体物,对弗氏柠檬酸杆菌(Citrobacter freundii)基因工程菌株生产紫色杆菌素的工艺条件进行了优化。通过单因素实验研究了培养基种类、培养温度、碳源、溶氧、种子液的状态、接种量、诱导时机、诱导剂的浓度及初始pH对细胞生长和紫色杆菌素产量的影响,通过正交实验研究了这些因素中可能存在交互作用的4个因素(种子液OD660、接种量、诱导时机、诱导剂浓度)的影响主次,确定了这些因素、水平的最佳搭配方案。结果表明,重组柠檬酸杆菌合成紫色杆菌素的最优培养条件为:种子液培养至OD660=3.6时,以3%的接种量接种于以甘油为碳源、初始pH为6.5的磷酸盐发酵培养基E2(25μg.ml-1卡那霉素),先在37℃、200r.min-1下培养至OD660=1.4,然后加入0.5μl.ml-1的诱导剂正辛烷,同时转入20℃,在150r.min-1下诱导培养31h。在此最优条件下,紫色杆菌素粗提物(紫色杆菌素及脱氧紫色杆菌素的混合物)产量可达1.809g.L-1,比优化前(0.514g.L-1)提高了252%,是目前国际上其他研究小组报道的最高摇瓶产量(0.43g.L-1)的4.2倍。质粒稳定性实验结果表明重组柠檬酸杆菌在抗生素选择压力条件下具有良好的遗传稳定性。     

Efficiency and Mechanism of Ciprofloxacin Hydrochloride Degradation in Wastewater by Fe3o4/Na2S2O8

ABSTRACT

The nanosized Fe₃O₄ catalyst was synthesized via a modified reverse coprecipitation method and characterized by means of a scanning electron microscope (SEM) and an X-ray diffraction (XRD) analysis instrument. The degradation efficiency and reaction rate of Fe₃O₄ in activating sodium persulfate used to degrade ciprofloxacin were determined from the catalyst dosage, oxidant concentration, and initial pH. The results showed that under the optimum conditions of a catalyst dosage of 2.0 g·L^?1, a sodium persulfate concentration of 1.0 g·L^?1, and an initial pH of 7, the degradation rate of ciprofloxacin was 93.73%, the removal rate of total organic carbon was 78%, and the first-order reaction constant was 0.06907 min^?1 within 40 min. It was also demonstrated that the reactive oxygen species in the Fe₃O₄/sodium persulfate catalytic system were mainly composed of SO₄^– and supplemented by OH· and HO₂· using probe compounds such as ethanol, tertiary butanol, and benzoquinone.     

Reductive removal of hexavalent chromium from aqueous solution using sepiolite-stabilized zero-valent iron nanoparticles: Process optimization and kinetic studies

We studied the optimization of hexavalent chromium (Cr(VI)) removal from aqueous solution using the synthesized zero-valent iron nanoparticles stabilized with sepiolite clay (S-ZVIN), under various parameters such as reaction time (min), initial solution pH and concentration of S-ZVIN (g·L^?1) using response surface methodology (RSM). The kinetic study of Cr(VI) was conducted using three types of the most commonly used kinetic models including pseudo zero-order, pseudo first-order, and pseudo second-order models. The rate of reduction reaction showed the best fit with the pseudo first-order kinetic model. The process optimization results revealed a high agreement between the experimental and the predicted data (R²=0.945, Adj-R²=0.890). The results of statistical analyses showed that reaction time was the most impressive factor influencing the efficiency of removal process. The optimum conditions for maximum response (98.15%) were achieved at the initial pH of 4.7, S-ZVIN concentration of 1.3 g·L^?1 and the reaction time of 75 min.     

Sequential optimization of culture medium composition for extracellular lipase production by Bacillus sphaericus using statistical methods

A sequential optimization strategy with the aid of statistical design of experiments was used to enhance the lipase (triacylglycerol acylhydrolases, EC 3.1.1.3) production by Bacillus sphaericus in submerged cultivation. A Plackett–Burman experimental design was used to evaluate the twelve medium components. Various vegetable oil inducers were tested for lipase production in the second step and the third step was to identify the optimal values of the significant medium components with sesame oil as the inducer using response surface methodology. A predictive model of the combined effects of the independent variables using response surface methodology and an artificial neural network was proposed. Unstructured kinetic models, a logistic model and a Luedeking–Piret model, were used to describe the cell mass and lipase production respectively. The significant variables affecting lipase production were found to be glucose, olive oil, peptone, NaCl and MnSO₄.H₂O. Sesame oil was found to be the best inducer for lipase production by Bacillus sphaericus. The maximum lipase activity of 4.45 U mL^?1, which was 1.5 times the maximum activity obtained in the Plackett–Burman experimental trials, was obtained at the optimum combination of medium constituents containing 12.695 g L^?1 glucose, 13.161 mL L^?1 sesame oil, 9.947 g L^?1 peptone, 3.25 g L^?1 NaCl, 0.5917 g L^?1 MnSO₄.H₂O and other insignificant components at the fixed level. The statistical design of experiments offers an efficient methodology to identify the significant variables and to optimize the factors with a minimum number of experiments for lipase production by Bacillus sphaericus. Copyright © 2007 Society of Chemical Industry     

Efficient production of <Emphasis Type="SmallCaps">d</Emphasis>-1,2,4-butanetriol from <Emphasis Type="SmallCaps">d</Emphasis>-xylose by engineered <Emphasis Type="Italic">Escherichia coli</Emphasis> whole-cell biocatalysts

We have developed a whole-cell bioconversion system for the production of d-1,2,4-butanetriol (BT) from renewable biomass. A plasmid pETduet-xylB-yjhG-T7-adhP-T7-mdlC was constructed and transformed to Escherichia coli BL21(DE3) to obtain the whole cells of E. coli BL21-XYMA capable of bioconversion d-xylose to BT. Then, the factors including carbon sources, nitrogen sources, metal ions, and culture conditions (pH, temperature, IPTG) were identified, and their effects on the whole-cell activity for BT production were investigated. To obtain the highest whole-cell activity, the optimal cultivation parameters are: 15 g·L^–1 yeast extract, 5 g·L^–1 sucrose, 3 g·L^–1 KH₂PO₄, 5 g·L^–1 NaCl, 3 g·L^–1 NH₄Cl, 0.25 g·L^–1 MgSO₄·7H₂O and 1 mL·L^–1 the mixture of trace elements. With the optimized whole cells of E. coli BL21-XYMA, 60 g·L^–1 of xylose was converted to 28 g·L^–1 BT with a molar yield of 66 %, which is higher than those reported in the biotechnological system.

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