Effect of cell volume on disintegration by ultrasonics

Wide variations in resistance to ultrasonic disintegration of continuously cultivated Bacillus cereus, Saccharomyces cerevisiae and Escherichia coli could be achieved by corresponding variations in fermenter impeller speed (agitation rate). In all cases examined, the relationship between disintegration constant and impeller speed was found to be linear. Although changes in relative strengths of E. coli were observed with changes in limiting nutrient (nitrogen-limited cells being weaker than carbon-limited cells for any one impeller speed), this was compensated for by the increased volumes of nitrogen-limited cells, and the relationship between disintegration constant and mean cell volume was linear, irrespective of nutrient limitation. Comparisons with other published data confirmed the view that for any one micro-organism, irrespective of cultural conditions, the principal determinand of susceptibility to ultrasonic disintegration was mean cell volume.     

Effects of changes in agitation rate on steady-state penicillinase titres in continuously-cultivated Bacillus cereus

Increases in agitation rates at a constant dilution rate in aerobic continuous culture of Bacillus cereus furnished corresponding increases in extracellular penicillinase titres. The ratio of titre to biomass supported by the apparatus increased when the agitation rate was raised, even if the medium was diluted to half its original concentration. Potential causes of the phenomenon are discussed.     

过硫酸钠和过硫酸钾的热稳定性分析

本文用绝热加速量热仪研究了过硫酸钠和过硫酸钾的热稳定性,得到了过硫酸钠和过硫酸钾的分解温度、压力随时间变化的曲线,分析了这两种物质的热分解过程,采用了速率常数法计算拟合了两种样品热分解过程的表观活化能Ea和指前因子A,并修正了实验结果,得出绝热条件下过硫酸钠的初始放热温度为156.38 ℃,最终放热温度为 293.01 ℃,最高温升速率为1451.88 ℃•min-1,到达最高温升速率的时间为358.13 mins,表观活化能为 227.11 kJ•mol-1; 而过硫酸钾的初始放热温度为139.07 ℃,最终温度为 289.74 ℃,最高温升速率为202.57 ℃•min-1,到达最高温升速率的时间为386.92 mins,表观活化能为170.68 kJ•mol-1。结果表明过硫酸钾更容易发生反应,热稳定性更差,但是过硫酸钠的反应更为剧烈。     

机械搅拌反应器中挡板的结构设计

研究了内径为0．786m的搅拌釜中挡板尺寸及结构对圆盘透平桨RT和翼型桨k5及其组合在气液两相中的气体分散与混合特性的影响。对不同形式的挡板的搅拌功率、气含率及气液混合特性进行了对比分析。研究结果表明：挡板尺寸结构应根据搅拌特性需要进行优化设计;挡板系数为0．12时,组合浆的功率输入已与同一转速下的全挡板系数时的功率输入相近,它同时可改善微观混合、提高混合效率：采用开槽挡板可提高复杂快反应的选择性,混合效率提高20％～25％。     

Determination of correlations to predict the minimum agitation speed for complete solid suspension in agitated vessels

Experiments were conducted to determine the effects of impeller clearance, impeller diameter, and other operating variables on the minimum agitation speed for off-bottom solid suspension in agitated vessels, N_js, for disc turbines (DTs) and flat-blade turbines (FBTs). Only data for which the impellers produced recirculation flows above and below the impeller (the so-called “double-eight” flow pattern) were considered. Regression equations for N_js were obtained, in which explicit terms for impeller clearance and vessel diameter-to-impeller diameter ratio (T/D) were included. Modified Zwietering equations (Zwietering, 1958) were also obtained, in which Zwietering's parameter S was mathematically expressed as a function of vessel diameter-to-impeller clearance ratio and T/D ratio. When used together with the correlations of Armenante and Uehara Nagamine (1998) for impellers close to the vessel bottom, the equations presented here can be used to calculate N_js for DTs and FBTs for any typical impeller clearance.     

Studies on para‐selectivity and yield enhancement in zeolite catalyzed toluene nitration

The nitration of toluene using solid acid catalyst is carried out in batch and semi‐batch reactors with or without continuous water withdrawal. The effect of process parameters viz., nature of catalyst, agitation speed, nitric acid‐toluene dispersion morphology, catalyst to toluene ratio, temperature, nitric acid dosing and boil‐up rates (BRs) on overall conversions, and para‐selectivity is investigated. The micro‐reaction environment around the catalyst particle and its influence on lattice aluminum transformation to achieve improved para‐selectivity has received special attention. These studies have established the importance of dispersion morphology of reactants and microenvironment around catalyst particles for achieving preferred conversion and para‐selectivity in toluene nitration.     

The effect of sodium dodecyl sulfate on mean drop size in a horizontal mixer–settler extractor

The effects of surfactant concentration, impeller speed, and holdup on mean drop diameter, D₃₂, during emulsification have been studied in a mixer–settler. Two well‐defined regions for the dependence of D₃₂ on surfactant concentration were observed. At low surfactant concentrations, D₃₂ decreased significantly with an increase in surfactant concentration, whereas D₃₂ did not depend on surfactant concentration at high surfactant concentrations. The decreasing rate of change of D₃₂ with impeller speed and the increasing rate of change of D₃₂ with holdup both decreased when a surfactant was added to the system. Moreover, an empirical correlation has been derived to predict D₃₂.     

Review on Mixing Characteristics in Solid‐Liquid and Solid‐Liquid‐Gas Reactor Vessels

Mechanically agitated reactors with single and multiple impeller systems are used in the industry for the various three‐phase mixing processes such as crystallization, fermentation, and hydrogenation, etc. The paper reviews the experimental work reported in the literature along with different techniques used for the measurement of the specific quantities such as minimum or critical impeller speed for solid suspension. The work critically surveys the literature and makes specific recommendations for the use of appropriate correlations and conditions to be used for the success of such equipment. This assessment will put all the relevant literature on a common footing and will help to validate work reported earlier.     

Influence of impeller type on hydrodynamics and gas‐liquid mass‐transfer in stirred airlift bioreactor

The influence of impeller type in a mechanically stirred airlift bioreactor was analyzed in relation to the non‐Newtonian viscous fluids. The agitation was carried out through a marine impeller (axial impeller) and a paddle impeller (radial impeller) located along with the gas sparger in the region comprised by the riser. The bioreactor was sparged with air under different velocities (0.036–0.060 m s^?1). Carboxymethylcellulose 1.94% and xanthan 1.80% were used as a fluid model. The gas holdup and volumetric mass‐transfer coefficient increased in up to five and three times, respectively, when compared to a conventional airlift bioreactor; however, better results were obtained when the straight paddle impeller type was used. The results suggest that the studied bioreactor can be used successfully in viscous fluid, and it can be more efficient than conventional airlift bioreactors. The results obtained suggest the use of radial impellers. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3159–3171, 2015     

不同碳源及通气条件下lpdA基因敲除对大肠杆菌代谢的影响

lpdA基因编码的lipoamide dehydrogenase是丙酮酸脱氢酶复合体、α-酮戊二酸脱氢酶复合体和甘氨酸裂解多酶体系的组成亚基之一.比较了不同碳源及通气条件下,lpdA基因敲除突变E. coli与野生E. coli的发酵特性,并通过对一些主要的酶活和胞内代谢产物浓度的测量,考察了lpdA基因敲除对E. coli代谢的影响.结果表明：葡萄糖为碳源的有氧条件下,lpdA基因的敲除导致丙酮酸、D-乳酸、L-谷氨酸的积累,TCA循环的抑制,乙醛酸途径和磷酸戊糖途径中的磷酸葡萄糖脱氢酶的激活.乙酸或丙酮酸为碳源的有氧发酵及葡萄糖为碳源的微氧发酵实验补充了以上的结论.     

大肠杆菌耐热元器件的构建及其应用

以提高大肠杆菌耐热性为目的,基于腾冲嗜热菌（Thermoanaerobacter tengcongensis MB4）热激蛋白基因 T.te-HSP20 构建了诱导型耐热元器件T7-T.te-HSP20 和组成型耐热元器件gapA-T.te-HSP20,转入大肠杆菌（Escherichia coli）获得工程菌 E. coli-TH 和 E. coli-GH。工程菌E. coli-TH在30℃和IPTG诱导下,目标蛋白呈可溶性表达,经50℃热激30 min后,存活率提高了3.2倍。高温发酵表明gapA-T.te-HSP20扩宽了工程菌E. coli-GH的最适生长温度的范围（37～43℃）,较大程度提高了大肠杆菌的耐热性。抗逆性分析还发现工程菌E. coli-GH具备了耐热与耐丁醇的双重功能,并有一定的抗乙酸和乙醇能力。为工业梯度升温发酵生产生物基产品的高效制造、节省成本提供了新思路。     

Changes in the structure of flax cellulose induced by solutions of lithium,sodium, and potassium hydroxides

In the reaction of cellulose-containing flax material with aqueous solutions of LiOH, NaOH, and KOH, the degree of swelling, sorption of water and alkali, parameters of the crystal lattice formed by alkali cellulose, degree of removal of lignin, and change in the degree of polymerization are a function of the type of cation. For the sorption characteristics and crystal lattice parameters of alkali cellulose, this dependence is determined by the change in the structure of the first and second hydrate shells of the cations. Despite the important differences in the degree of swelling, crystal lattice parameters of alkali cellulose, and degree of removal of lignin, the changes in the crystal structure of the cellulose related to the transition from crystalline modification I to modification II under the effect of the three different bases are similar and take place in approximately the same concentration region.Translated from Khimicheskie Volokna, No. 6, pp. 15–19, November–December, 2004.     

Facile, reagentless and in situ release of Escherichia coli intracellular enzymes by heat-inducible autolytic vector for high-throughput screening

In an effect to broaden the application of the heat-inducible autolytic vector pUC18-cI857/p(R)-SRRz-rrnB previously developed, a new vector pUC18-cI857/p(R)(T41C)-SRRz-rrnB (pEAS-1b) was quantitatively characterized under various growth temperatures, heat induction temperatures and durations, and IPTG (isopropyl beta-d-thiogalactoside) induction times, after resolving its erratic lysis profile found previously. Escherichia coli BL21 cells harboring this vector grew well at temperatures <36 degrees C, and lysed efficiently (97.0 +/- 0.8%) just 0.5 h after heat induction at 42 degrees C for 30 min when cell growth was performed at 35 degrees C. Application of this autolytic vector either in 96-well plates, or on nitrocellulose membranes, or on agar plates led to facile, efficient and consistent release of intracellular recombinant enzymes (e.g., a lysis efficiency of 91.8 +/- 1.1% was obtained in 96-well plates). Further application in directed evolution was illustrated by improving the thermostability of amadoriase using this vector. This reagentless and in situ cell lysis method has the potentials for lysis of miniaturized samples in clinical diagnosis and bioanalytical detection, and even for lysis of cells in the microarray format.     

Deactivation kinetics of Escherichia coli cells correlated with intracellular superoxide dismutase activity in photoreaction with titanium dioxide particles

In the photoreaction of Escherichia coli IM303 (superoxide dismutase (SOD)‐deficient mutant) and MM294 (wild‐type strain) with TiO₂ particles, the viability of strain IM303 decreased linearly with photoreaction time, while the time profile of the viability of strain MM294 exhibited a curved form. Using strain MM294 with varied initial SOD activities, the TiO₂ photoreaction tests were conducted at incident light intensities of I₀ = 4,8 and 14 W m^?2, and the time profiles of bacterial viabilities were analyzed on the basis of the series‐event model. The value of n (corresponding to the step number in the series reaction kinetics described by the model) increased with an increase in initial SOD activity (A_SOD,0), giving a mean value of A_SOD,0/n = 7.1 × 10^?9 U cell^?1 under the conditions examined. SOD activities in the cells of strain MM294 with A_SOD,0 = 1.9 × 10^?8 and 4.0 × 10^?8 U cell^?1 decreased with the progress of photoreaction conducted at I₀ = 14 W m^?2. The transition of intracellular SOD activities expressed was in agreement with the observed data by considering the changes in bacterial cell populations with varied SOD activities based on the proposed model. © 2002 Society of Chemical Industry     

Oxidation of intracellular and extracellular fatty acids in skeletal muscle

Fatty acids are a major fuel for many tissues, and abnormal utilization is implicated in diseases. However, tissue fatty acid oxidation has not been determined reliably in vivo. Furthermore, fatty acid oxidation has not been partitioned into intracellular and extracellular components. In this report, a one‐pool model is described that enables direct quantitation of fluxes of intracellular and plasma fatty acids to mitochondria in skeletal muscle using dual stable isotopes and liquid chromatography/electrospray ionization ion‐trap tandem mass spectrometry technology. It is validated by the determination of palmitate oxidation by skeletal muscle in lean and obese rats and the regulation by insulin. Resting postabsorptive intramyocellular and plasma palmitate oxidation by the gastrocnemius muscle was determined to be 3.47 ± 0.8 and 2.06 ± 0.5 nmol/g/min in lean and 6.96 ± 1.8 and 1.34 ± 0.2 nmol/g/min in obese rats, respectively. In obese rats, hyperinsulinemia (1 nmol/L) suppressed intramyocellular (by 59 ± 5% to 2.88 ± 0.3 nmol/g/min; p <0.05) but not plasma (1.41 ± 0.14 nmol/g/min; p >0.05) palmitate oxidation. The fractional turnover rate of palmitoylcarnitine (0.34 ± 0.1/min vs. 0.83 ± 0.2/min; p <0.05) was also suppressed by insulin in obese rats. In obese and lean rats, 83 and 51%, respectively (p = 0.08), of plasma fatty acids traverse the triacylglycerol pool before being oxidized. The results demonstrated that the methodology is feasible and sensitive to metabolic alterations and thus can be used to study fatty acid utilization at tissue level in vivo in a compartmentalized manner for the first time.     

甘油连续生物歧化过程的过渡行为及其数学模拟

用肺炎杆菌将甘油转化为１,３－丙二醇过程对稀释速率和底物进料浓度变化的过渡行为反映了细胞生长和胞内物质代谢在不同条件下存在着显著的差异。体系的过渡响应取决于操作条件变化前后系统所处的状态,当底物浓度由限制状态向剩余状态过渡时,甘油的残余浓度不断上升,而乙醇的浓度则逐渐下降,同时生物量、１,３－丙二醇和乙酸的浓度呈现先增后降的趋势。本文用“甘油浓度变化速率”的概念修正了菌体生长模型,并对甘油歧化过程     

工业三相浆态反应器内的混合与操作

根据搅拌糟中气－液－固三相混合性能的研究，论述了工业三相浆态反应器内对气体、液体和固体的分散（混合）要求，据此对工业三相浆态反应器中叶轮的结构和搅拌浆的启动进行了讨论。     

重组大肠杆菌高密度发酵生产类人胶原蛋白的过程控制研究

Recombinant E. coli BL 21 was cultivated in high cell density to produce human-like collagen. The effects of the feeding of nitrogen source, controlled by an auto on/off-feeding mode with two different cycles of 0.5min and 4min intervals, oxygen-enrichment methods and inducement strength on the cell yield and human-like collagen production were investigated. The studies showed that nitrogen source feeding in fast cycle could result in higher human-like collagen production than that in slow cycle; and the feedback regulation of glucose, increase of the pressure of fermentation bioreactor, and supply of oxygen-enriched air could all increase cell yield and human-like collagen production. The effects of inducement strength on protein expression were found important. When OD600 reached 90-100, the cultivation temperature was increased to 42℃ to begin induction for 2-3 h, and then shifted to 39℃ for 5-6h induction, the cell density and human-like collagen production could reach 96g·L-1 [DCW (dry cell mass)