三段式谷氨酸棒杆菌发酵生产生物絮凝剂的过程及动力学模拟(英文)

Fermentation of bioflocculant with Corynebacterium glutamicum was studied by way of kinetic modeling. Lorentzian modified Logistic model, time-corrected Luedeking–Piret and Luedeking–Piret type models were pro-posed and applied to describe the cell growth, bioflocculant synthesis and consumption of substrates, with the correlation of initial biomass concentration and initial glucose concentration, respectively. The results showed that these models could well characterize the batch culture process of C. glutamicum at various initial glucose con-centrations from 10.0 to 17.5 g·L?1. The initial biomass concentration could shorten the lag time of cel growth, while the maximum biomass concentration was achieved only at the optimal initial glucose concentration of 16.22 g·L?1. A novel three-stage fed-batch strategy for bioflocculant production was developed based on the model prediction, in which the lag phase, quick biomass growth and bioflocculant production stages were sequentially proceeded with the adjustment of glucose concentration and dissolved oxygen. Biomass of 2.23 g·L?1 was obtained and bioflocculant concentration was enhanced to 176.32 mg·L?1, 18.62% and 403.63%higher than those in the batch process, respectively, indicating an efficient fed-batch culture strategy for bioflocculant production.     

重组大肠杆菌流加发酵中短暂溶氧休克促进5-氨基乙酰丙酸生成(英文)

5-Aminolevulinic acid （ALA） is a common precursor for tetrapyrrole compounds in all kinds of organ isms and has wide applications in agriculture and medicines. In this study, a new strategy, i.e. short-term dissolved oxygen （DO） shock during aerobic fermentation, was introduced to produce 5-aminolevulinic acid with a recombi-nant E. coli. Effects of duration time of DO shock operation on plasmid concentration, intracellular ALA synthase （ALAS） activity and ALA production were investigated in Erlenmeyer shake flasks. The results indicated that both ALAS activity and ALA yield were enhanced in an anaerobic operation of 45 rain in the early exponential phase during fermentation, while they decreased when the anaerobic operation time was further increased to 60 rain. The DO shock protocol was confirmed with the fed-batch fermentation in a 15 L fermenter and the ALA production achieved 9.4 g.L-1 （72 mmol.L-1）, which is the highest yield in the fermentation broth reported up to now.     

Reduction of foaming and enhancement of ascomycin production in rational Streptomyces hygroscopicus fermentation

Foaming reduces the working volume and limits the biosynthesis of macrolide immunosuppressant ascomycin (FK520) in the batch fermentation process of Streptomyces hygroscopicus FS-35 in a 7.5 L bioreactor. To find the relation between FK520 production and foaming, effects of 10 fermentation parameters including organic acids and membrane permeability were investigated. The results suggest that acetate accumulation caused by short period oxygen deficiency and fast consumption of glucose is the reason for increased foaming and declined FK520 production. Therefore, a fed-batch fermentation strategy was developed to reduce the accumulation of ac-etate. After optimization, the maximum acetate concentration dropped from 320 mg·L?1 to 157 mg·L?1, de-creased by 50.8%, and the maximum foam height reduced from 5.32 cm to 3.74 cm, decreased by 29.7%, while the maximum FK520 production increased from 375 mg·L?1 to 421 mg·L?1, improved by 12%.     

Kinetics of Asymmetric Reduction of Phenylglyoxylic Acid to R-(－)-Mandelic Acid by Saccharomyces Cerevisiae FD11b

The kinetics of asymmetric production of R-(-)-mandelic acid (R-MA) from phenylglyoxylic acid (PGA)catalyzed by Saccharomyces cerevisiae sp. strain FD11b was studied by fed-batch cultures. The concentrations of glucose and PGA were controlled respectively with a dual feeding system. When the electron donor glucose was supplied at the rate of 0.0833mmol·gdw-1·h-1, the specific production rate (qp) and the enantiomeric excess of R-MAreached the maximum 0.353mmol·gdw-1·h-1 and 97.1％, respectively. The apparent reduction activity of yeast FD11b was obviously affected by both substrate PGA and product MA. The qp value reached the maximum 0.36-0.38mmol·gdw-1·h-1 when the PGA concentration was controlled between 25 and 35mmol·L-1. The obvious substrate inhibition of bioconversion was observed at the PGA concentrations higher than 40mmol· L-1. The accumulation of product MA also caused a severe feed-back inhibition for its production when the product concentration was above 60mmol· L-1. The kinetic model with the inhibition effect of both substrate and product was simulated by a computer-based least-square arithmatic. The established kinetic model was in good agreement with the experimental data.     

应用群能量恒定粒子群优化算法的批次流加发酵过程批次间优化(英文)

An iterative optimization strategy for fed-batch fermentation process is presented by combining a run-to-run optimization with swarm energy conservation particle swarm optimization (SEC-PSO). SEC-PSO, which is designed with the concept of energy conservation, can solve the problem of premature convergence frequently appeared in standard PSO algorithm by partitioning its population into several sub-swarms according to the energy of the swarm and is used in the optimization strategy for parameter iden-tification and operation condition optimization. The run-to-run optimization exploits the repetitive nature of fed-batch processes in order to deal with the optimal problems of fed-batch fermentation process with inaccurate process model and unsteady process state. The kinetic model parameters, used in the operation condition optimization of the next run, are adjusted by calculating time-series data obtained from real fed-batch process in the run-to-run optimization. The simulation results show that the strategy can adjust its kinetic model dynamically and overcome the instability of fed-batch process effectively. Run-to-run strategy with SEC-PSO provides an effective method for optimization of fed-batch fermentation process.     

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.     

Enhanced cold active lipase production by metagenomic library recombinant clone CALIP3 with a step-wise temperature and dissolved oxygen level control strategy

A metagenomic library recombinant clone CAPL3, an Escherichia coli strain generated by transformed with metagenomic library from deep-sea sediments, can efficiently produce cold active lipase. The effects of both temperature and dissolved oxygen(DO) on cold active lipase production by batch culture of metagenomic library recombinant clone(CAPL3) from deep-sea sediment were investigated. First, a two-stage temperature control strategy was developed, in which the temperature was kept at 34 °C for the first 15 h, and then switched to30 °C. The cold active lipase activity and productivity reached 315.2 U·ml~(-1)and 8.08 U·ml~(-1)·h~(-1), respectively,increased by both 14.5% compared to the results obtained with temperature controlled at 30°C. In addition, different DO control modes were conducted, based on the data obtained from the different DO control strategies and analysis of kinetics parameters at different DO levels. A step-wise temperature and DO control strategy were developed to improve lipase production, i.e., temperature and DO level were controlled at 34 °C, 30% during 0–15 h;30 °C, 30% during 15–18 h, and 30 °C, 20% during 18–39 h. With this strategy, the maximum lipase activity reached 354.6 U·ml~(-1)at 39 h, which was 28.8% higher than that achieved without temperature and DO control(275.3 U·ml~(-1)).     

一种新的生产计划与催化裂化装置过程操作集成的闭环策略

Production planning models generated by common modeling systems do not involve constraints for process operations, and a solution optimized by these models is called a quasi-optimal plan. The quasi-optimal plan cannot be executed in practice some time for no corresponding operating conditions. In order to determine a practi- cally feasible optimal plan and corresponding operating conditions of fluidized catalytic cracking unit （FCCU）, a novel close-loop integrated strategy, including determination of a quasi-optimal plan, search of operating conditions of FCCU and revision of the production planning model, was proposed in this article. In the strategy, a generalized genetic algorithm （GA） coupled with a sequential process simulator of FCCU was applied to search operating conditions implementing the quasi-optimal plan of FCCU and output the optimal individual in the GA search as a final genetic individual. When no corresponding operating conditions were found, the final genetic individual based correction （FGIC） method was presented to revise the production planning model, and then a new quasi-optimal production plan was determined. The above steps were repeated until a practically feasible optimal plan and corresponding operating conditions of FCCU were obtained. The close-loop integrated strategy was validated by two cases, and it was indicated that the strategy was efficient in determining a practically executed optimal plan and corresponding operating conditions of FCCU.     

L-半胱氨酸浓度对氧化还原电位和生物产氢过程的影响(英文)

The effects of L-cysteine concentration on biohydrogen production by Enterobacterium Bacterium M580 were investigated in batch cultivation.The experimental results showed that L-cysteine could enhance the cell growth,hydrogen production rate and hydrogen yield when its concentration was less than 500 mg·L-1,while it had negative effects when its concentration was higher than 500 mg·L-1.The hydrogen production was the highest 1.29 mol·mol-1(H2/glucose) when 300 mg·L-1L-cysteine was added into the culture,and the yield was 9.4% higher than that in the control.The oxidation-reduction potential(ORP) ,which was influenced by L-cysteine,also affected hydrogen production.The ORP values were in the range-300 mV to-150 mV when the L-cysteine concentration was higher than 500 mg·L-1.Although the ORP in this range was favorable for hydrogen production,it was not suitable for the biomass growth.Hence,less hydrogen was produced.When the L-cysteine concentration was lower than 500 mg·L-1,the ORP was more suitable for both biomass growth and hydrogen production.In addition,at least 91%glucose was consumed when L-cysteine was added to the culture media,compared to the 97.37% consumption without L-cysteine added.     

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.     

Adsorptive potential of Acacia nilotica based adsorbent for chromium(Ⅵ) from an aqueous phase

The objective of this research was to enhance adsorption capacity of Acacia nilotica(keekar) sawdust for the abatement of chromium bearing wastewater and to investigate the effect of process parameters on adsorption capacity. The sawdust was activated by acid wash and functionalized subsequently with formaldehyde.Functionalization of activated sawdust raised its chromium removal efficiency of almost 10% as compared to its adsorption removal efficiency of HCl treated sawdust in a batch adsorption study. Adsorption kinetic data provided better fitting with pseudo second order model. Maximum adsorption capacity calculated through the best fitting Langmuir model was 6.34 mg·g~(-1) and 8.2 mg·g~(-1) for HCl treated and formaldehyde functionalized sawdust adsorbents, respectively. The adsorption of Cr(Ⅵ) was endothermic when studied by varying temperature from 20 °C to 50 °C for both activated and functionalized adsorbents.     

限制曝气实现常温条件下生活污水短程硝化

The objective of this paper was to examine the feasibility of partial nitrification from raw domestic wastewater at ambient temperature by aeration control only. Airflow rate was selected as the sole operational parameter. A 14L sequencing batch reactor was operated at 23℃ for 8 months, with an input of domestic wastewater. There was a prolgrammed decrease of the airflow rate to 28L·h^-1, the corresponding average dissolved oxygen （DO） was 0.32mg·h^-1, and the average nitrite accumulation rate increased to 92.4% in 3 weeks. Subsequently, further increase in the airflow rate to 48L·h^-1 did not destroy the partial nitrification to nitrite, with average DO of 0.60mg·h^-1 and nitrite accumulating rate of 95.6%. The results showed that limited airflow rate to cause oxygen deficiency in the reactor would eventually induce only nitrification to nitrite and not further to nitrate and that this system showed relatively stability at higher airflow rate independent of pH and temperature. About 50% of influent total nitrogen was eliminated coupling with partial nitrification, taking the advantage of low DO during the reaction.     

Ralstonia eutropha批式流加培养生产羟基丁酸-丙酸混合聚酯中丙酸进料优化研究

The feeding method of propionic acid for production of poly (3-hydroxybutyrate-co-3-hydro xyvalerate)[P(3HB-co-3HV)]by fed-batch culture of Ralstonia eutropha was optimized to achieve high cell density and high 3HV yield,Effects of different feeding strategies of propionic acid on the production of P(3HB-co-3HV) were investigated,A decline of specific synthesis rate of copolymer and the yield of 3HV unit from propionic acid were observed due to the propionic acid accumulation in culture broth when the feeding solution with high P/G(ropionic acid to glucose) ration was employed,It was further confirmed by controlling propionic acid concentration at a low leve in the separate feeding of propionic acid.An optimed feeding strategy was demonstrated to reduce the propionic acid accumulation ,The cell concentration,P(3HB-co-3HV) productivity and 3HV unit fraction reached to 163.9 kg.m^-3,1.8kg.m^-3.h^-1,and 10.6%(by mass),respectively,resulting in a yield of 0.33g HV per g propionic acid.     

Optimization of Propionic Acid Feeding for Production of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) in Fed-Batch Culture of Ralstonia eutropha

The feeding method of propionic acid for production of poly(3-hydroxybutyrate-co-3-hydro xyvalerate) [P(3HB-co-3HV)] by fed-batch culture of Ralstonia eutropha was optimized to achieve high cell density and high 3HV yield. Effects of different feeding strategies of propionic acid on the production of P(3HB-co-3HV) were investigated. A decline of specific synthesis rate of copolymer and the yield of 3HV unit from propionic acid were observed due to the propionic acid accumulation in culture broth when the feeding solution with high P/G(propionic acid to glucose) ratio was employed. It was further confirmed by controlling propionic acid concentration at a low level in the separate feeding of propionic acid. An optimal feeding strategy was demonstrated to reduce the propionic acid accumulation. The cell concentration, P(3HB-co-3HV) productivity and 3HV unit fraction reached to 163.9kg.m-3, 1.8kg.m-3.h-1, and 10.6%(by mass), respectively, resulting in a yield of 0.33g HV per g propionic acid.     

黄孢原毛平革菌固态发酵木薯渣生产锰过氧化物酶及其脱色靛蓝(英文)

Bioconversion of lignocellulosic wastes to higher value products through fungal fermentation has economic and ecological benefits. In this study, to develop an effective strategy for production of manganese peroxidase (MnP) from cassava residue by Phanerochaete chrysosporium in solid state fermentation, the stimulators of MnP produc-tion were screened and their concentrations were optimized by one-at-a-time experiment and Box–Behnken design. The maximum MnP activity of 186.38 nkat·g?1 dry mass of the sample was achieved after 6 days of fer-mentation with the supplement of 79.5 mmol·L?1·kg?1 acetic acid, 3.21 ml·kg?1 soybean oil, and 28.5 g·kg?1 alkaline lignin, indicating that cassava residue is a promising substrate for MnP production in solid state fermen-tation. Meanwhile, in vitro decolorization of indigo carmine by the crude MnP was also carried out, attaining the ratio of 90.18%after 6 h of incubation. An oxidative mechanism of indigo carmine decolorization by MnP was pro-posed based on the analysis of intermediate metabolites with ultra-high performance liquid chromatography and gas chromatography tandem mass spectrometry. Using the crude MnP produced from cassava residue for indigo carmine decolorization gives an effective approach to treat dyeing effluents.     

重组大肠杆菌分批-补料高密度发酵生产类人胶原蛋白的动力学

The kinetics of batch and fed-batch cultures of recombinant Escherichia coli producing human-like collagen was investigated. In the batch culture, a kinetic model of a simple growth-association system was concluded without consideration of cell endogeneous metabolism. The cell lag time, the maximum specific growth rate and Yx/s were determined as 1.75h, 0.65h^-1 and 0.51g·g^-1, respectively. In the fed-batch culture, different specific growth rates were set at （0.15, 0.2, 0.25h^-1） by the method of pseudo-exponential feeding, and the expressions for the specific rate of substrate consumption, the growth kinetics and the product formation kinetics of each phase were obtained. The result shows that the concentrations of cell and product can reach 77.5g·L^-1 and 10.2g·L^-1 respectively. The modal predictions are in good agreement with the experimental data.     

Improvement of the riboflavin production by engineering the precursor biosynthesis pathways in Escherichia coli

3,4-Dihydroxy-2-butanone 4-phosphate (DHBP) and GTP are the precursors for riboflavin biosynthesis. In this research, improving the precursor supply for riboflavin production was attempted by overexpressing ribB and engineering purine pathway in a riboflavin-producing Escherichia coli strain. Initially, ribB gene was overexpressed to increase the flux from ribulose 5-phosphate (Ru-5-P) to DHBP. Then ndk and gmk genes were overexpressed to enhance GTP supply. Subsequently, a R419L mutation was introduced into purA to reduce the flux from IMP to AMP. Finally, co-overexpression of mutant purF and prs genes further increased riboflavin production. The final strain RF18S produced 387.6 mg riboflavin · L?1 with a yield of 44.8 mg riboflavin per gram glucose in shake-flask fermentations. The final titer and yield were 72.2%and 55.6%higher than those of RF01S, respectively. It was concluded that simultaneously engineering the DHBP synthase and GTP biosynthetic pathway by rational metabolic engineering can efficiently boost riboflavin production in E. coli.     

Effect of interlayer anions on chromium removal using Mg–Al layered double hydroxides:Kinetic,equilibrium and thermodynamic studies

The influence of interlayer anions such as NO3-, SO42-and Cl-on Mg–Al hydrotalcites for Cr(VI) removal from aqueous solution was studied. The structure of the prepared LDHs was characterized by XRD, SEM, FTIR, TGA, BET surface area and p Hzpc. The sorbent ability and sorption mechanisms were also investigated. The LDHs exhibit high removal for Cr(VI), and the sorbed amount depends on the nature of interlayer anion, which decreased in the following order: NO3-N Cl-N SO42-. Nitrate-containing LDH reached a Cr(VI) sorption equilibrium within only 30 min. The effects of operating conditions, including initial concentration, solution p H, agitation time and sorbent amount have been studied in batch mode. The optimum conditions were observed at an initial concentration of 100 mg·L-1, p H = 6, agitation time of 60 min and a sorbent dose of 2 g·L-1. The equilibrium data were fitted to the Langmuir, Freundlich and Dubinin–Radushkevich isotherm models. The Langmuir model was found to sufficiently describe the sorption process, offering a maximum sorption capacity of 71.91 mg·g-1. The sorption kinetic follows pseudo-second-order reaction with high accuracy. Thermodynamic parameters suggested that the sorption process is spontaneous and endothermic in nature.     

葡萄糖及磷酸盐对刺糖多孢菌多杀菌素发酵的影响

The effects of glucose and inorganic phosphate on mycelium growth and spinosad production with Saccharopolyspora spinosa were studied. The results showed that the increase of glucose concentration from 18.6g·L-1 to 58.8g·L-1 could promote the mycelium growth and spinosad production. And when the glucose concentration increased from 58.8g·L-1 to 79.6g·L-1, no obvious change was detected but a slight drop in spinosad production was observed, whereas, when the glucose concentration increased from 79.6g·L-1 to l15.3g·L-1, substantial decrease in both mycelium growth and spinosad production occurred. The increase of phosphate conccntration from 3.68mmol· L-1 to 29.41mmol·L-1 rendered corresponding increase in mycelium growth and spinosad production. When phosphate concentration increased from 29.41mmol· L-1 to 44.12mmol·L-1, mycelium growth slightly increased and spinosad production dropped, while when phosphate concentration increased from44.12mmol·L-1 to 57.62mmol·L-1, both mycelium growth and spinosad production decreased sharply. Conclusively,the optimal initial concentration of glucose and phosphate is 58.8g·L-1 and 29.41mmol·L-1, respectively. The spinosad fermentation in the production medium containing 58.8g·L-1 glucose and 29.41mmol·L-1 phosphate was scaled up in 5-L fermentation and the spinosad production reached 507mg·L-1, which was 28% higher than that in the flask fermentation.     

Production of 2,3-Butanediol by Klebsiella Pneumoniae Using Glucose and Ammonium Phosphate

The production of 2,3-butanediol by Klebsiella pneumoniae from glucose supplemented with different salts was studied. A suitable medium composition was defined by response surface experiments. In a medium containing glucose and （NH4）2HPO4, the strain could convert 137.0g of glucose into 52.4g of 2,3-butanediol and 8.4g of acetoin in shaking flasks. The diol yield amounted to 90% of its theoretical value and the productivity was 1-1.5g.L^-1.h^-1. In fed-batch fermentation, the yield and productivity of diol were further enhanced by maintaining the pH at 6.0. Up to 92.4g of 2,3-butanediol and 13.1g of acetoin per liter were obtained from 215.0g of glucose per liter. The diol yield reached 98% of its theoretical value and the productivity was up to 2.1g.L^-1.h^-1.