红豆杉细胞反应器悬浮培养氧传质系数的研究

氧传质系数是表征反应器操作性能的重要参数,是反应器优化设计和放大的关键,植物细胞培养液中的氧传质系数与纯水或模拟溶液有很大差异,必须在实际培养过程中在线进行氧传质系数的研究。为了快速、准确地测量实际培养液的氧传质系数,基于动态法恢复通气后的溶氧质量浓度-时间数据,提出了确定氧传质系数和饱和溶氧质量浓度的新方法,进而测定了10 L通气搅拌反应器中红豆杉细胞悬浮培养过程的氧传质系数,研究了氧传质系数、细胞的摄氧率和细胞的比耗氧速率的变化规律。结果表明:通气量对氧传质系数的影响大于搅拌转速对氧传质系数的影响;随着细胞生物量增加,氧传质系数减少、摄氧率增加,比耗氧速率先增加后缓慢下降;建立了氧传质系数kLa与单位体积的功率输入N3D2和空气表观线速度vS的关联式和氧传质系数kLa与细胞生物量X的关联式。     

新型气力搅拌式生物反应器的实验研究

为了研制培养微生物和动植物细胞或组织的生物反应器,采用微孔橡胶膜片装置使产生的搅拌剪切力较低,以满足溶氧需求较高、介质密度较高、同时具有较高黏度的液体介质的搅拌要求.实验过程中,对生物反应器进行了流动特性观察、压力损失、反应器内含气率及溶氧质量浓度的测量等实验,选取了综合性能较好的微孔橡胶膜片.结果表明:这种生物反应器...     

三相循环流化床中的气液相界面积和传质系数

采用溶氧法测量了三相循环流化床中液相溶氧浓度的轴向分布,并按轴向扩散模型处理实验数据,优化得到气液体积传质系数kLa,同时用光纤探头测量了体系中的气含率和气泡大小分布,计算得到了气液相界面积a和气液传质系数kL,并研究了主要操作条件(表观气速、表观液速和固含率)对气液传质系数的影响规律.     

共生菌系TSH06连续发酵生产丁醇

传统的产丁醇生产菌均为严格厌氧,本实验室分离出一株兼性厌氧共生菌系TSH06,可在微氧条件下发酵生产丁醇。本文研究了共生菌系TSH06微氧条件下的丁醇连续发酵,考察了稀释率对TSH06细胞生长及丁醇合成的影响。结果表明,低稀释率有利于丁醇的生成,高稀释率有利于酸的积累,丁醇浓度随着稀释率的增大而减小,而生产强度随稀释率的增大而增大。当稀释率大于0.2h~(–1)时,生产强度呈下降趋势。最优化的稀释率为0.2h~(–1),丁醇生产强度可达1.06g/(L·h)。研究结果可为微氧条件下丁醇连续发酵的进一步优化提供理论依据。     

高单体进料浓度下丙烯腈连续水相沉淀共聚的研究Ⅱ聚合物颗粒形态

以ＫＰＳ－ＮａＨＳＯ３－Ｆｅ２＋ 为引发体系,在５ 升ＣＳＴＲ 中进行了高单体进料浓度（＞ ２８％ ）的丙烯腈（ＡＮ）－丙烯酸甲酯（ＭＡ）－苯乙烯磺酸钠（ＳＳＳ）三元连续水相沉淀共聚,系统考察了搅拌条件、单体进料浓度、引发剂浓度及配比、ｐＨ 值、平均停留时间和聚合温度等工艺因素对聚合物颗粒形态的影响。结果表明,有利于提高聚合反应速率的因素,包括提高单体进料浓度、引发剂浓度、ｐＨ值和聚合温度等均有利于改善颗粒形态,其中搅拌强度和单体进料浓度影响最明显。适当延长平均停留时间也对颗粒形态稍有改善。     

溶析结晶法脱除钛白废酸中硫酸亚铁盐的研究

针对钛白粉工业的废酸,选用乙醇(Et OH)为溶析剂,研究了溶析结晶法脱除钛白废酸中硫酸亚铁盐的可行性。在5~30℃,采用激光检测法系统地测定了七水硫酸亚铁在水、硫酸溶液和醇酸混合水溶液中的溶解度,考察了溶析剂浓度、温度、硫酸浓度等因素对硫酸亚铁盐溶解度的影响。在此基础上,以钛白废酸(含硫酸20%(wt)、七水硫酸亚铁8%(wt)为对象,在搅拌结晶器中考察了溶析剂加入量、加入方式、搅拌速度、晶种和熟化时间等工艺操作条件对硫酸亚铁脱除率的影响。结果表明,以乙醇为溶析剂,可在常温下显著降低硫酸亚铁在硫酸溶液中的溶解度。在醇酸混合水溶液中,硫酸亚铁盐的溶解度主要受溶析剂浓度影响,与硫酸浓度无关。控制适宜的搅拌速度、溶析剂加入速度和熟化时间有助于提高硫酸亚铁的脱除率。适宜的溶析结晶条件为:温度为5~10℃,溶析剂与废酸的质量比1:1,溶析剂加料速度6 m L·min-1、熟化时间60 min。在此条件下,七水硫酸亚铁的脱除率可达到87%~91%。     

Al - Ferron逐时络合比色法在铝溶胶黏结剂聚合形态分析中的应用

将Al - Fenon逐时络合比色法应用于催化剂黏结剂铝溶胶的铝形态分布测定,研究不同特点铝溶胶样品的铝形态分布,考察实验温度、样品稀释浓度和稀释后放置时间等因素对测定结果的影响.结果表明,实验温度、样品稀释浓度、稀释后放置时间对A系列样品的测定结果有影响,而对B系列样品的测定结果几乎无影响.在原有方法基础上,规定了测...     

强化好氧颗粒污泥稳定性的研究进展

系统回顾了有关好氧颗粒污泥稳定性方面的研究进展,简要介绍了好氧颗粒污泥的形成机理,主要包括“丝状菌假说”、“胞外聚合物假说”、“选择压驱动假说”、“自凝聚假说”;着重分析了影响好氧颗粒污泥稳定性的主要因素有温度、pH值、有机负荷率与氨氮浓度、溶解氧与颗粒粒径、饱食-饥饿期、水力剪切力、污泥龄和有毒有害物质等;详细论述了抑制丝状膨胀、促进胞外聚合物的分泌、富集慢速增长的微生物和强化颗粒内核等措施可以强化好氧颗粒污泥的稳定性,并提出了对好氧颗粒污泥的形成机理以及功能菌群进行更深入的研究将会是今后的研究重点,进而为好氧颗粒污泥的工业化应用作铺垫。     

柠檬酸发酵罐内气泡流的数值模拟分析

运用气泡多相流MUSIG(multiple-size-group)数学模型,以100 m3的传统柠檬酸发酵罐内的搅拌、气泡运动过程为研究对象,针对直径为20、5、0.5 mm的3种典型气泡尺寸组,采用CFD技术数值模拟出罐内的湍流速度场、气泡体积组分空间分布场.探讨了不同的通气量对气泡体积分布的影响规律性,分析了发酵罐内溶氧浓度低的主要原因,为认识与改善发酵罐内的溶氧率提供了理论依据.     

微观混和问题的研究——(Ⅴ)混和对沉淀反应过程的影响

以硫酸钡沉淀反应为工作体系,研究了在搅拌釜中搅拌强度、粘度、加料时间、反应物初始浓度及反应物初始体积比等各种操作参数对产物晶体粒度分布的影响。发现:搅拌强度、粘度以及加料时间对粒度分布的影响不是单调的,均各自存在极小值点,在极小值临界点处平均粒径或方差(或变异系数)取值最小;平均粒径取值最小处的临界点与方差(或变异系数)取值最小处的临界点并不相重而稍有偏离,但在两个临界点所围的操作区内,粒子细而且分布均匀,所以此区为最佳操作区,这一结果对液相法超细粒子的制备而言显得极为重要。     

Effects of process parameters on heterologous protein production in Aspergillus niger fermentation

Filamentous fungi such as Aspergillus niger are attractive hosts for recombinant DNA technology because of their ability to secrete bioactive proteins with post‐translational processing such as glycosylation. Foreign genes can be incorporated into the chromosomes of the filamentous fungi, providing superior long‐term genetic stability. However, heterologous protein production is often severely hampered by fungal proteases. In this work, a recombinant Aspergillus niger strain AB4.1[pgpdAGLAGFP]#11 which carries a glucoamylase (GLA)‐green fluorescent protein (GFP) fusion gene was selected as a model system to study the effects of bioprocess parameters—agitation intensity, initial glucose concentration, initial yeast extract concentration, and dissolved oxygen tension (DO)—on extracellular protease inhibition and heterologous protein production. Based on previous experimental experience and results, a 2^4–1 fractional factorial design was applied to the experiments. Each parameter was tested at two levels. It was found that agitation affected the GFP production most significantly. Higher agitation rate resulted in higher GFP production. Protease activity was most influenced by initial glucose concentration and DO. Fungal morphology was also affected by these parameters. The effects of these parameters on pellet size and pellet porosity are discussed. Copyright © 2003 Society of Chemical Industry     

Regeneration of spent earth by wet oxidation

Regeneration of deoiled spent earth by wet oxidation has been investigated. Molecular oxygen was used as an oxidizing agent. Effects of operating parameters such as speed of agitation, temperature, oxygen partial pressure, slurry concentration, and cycle of regeneration have been studied. Kinetics of regeneration was found to be first order with substrate concentration and also with dissolved oxygen concentration. Decolorization capacity of regenerated earth was the same as that of its virgin bleaching earth. Adsorption isotherm data was fitted in Freundlich equation. The values of Freundlich constants of regenerated earth were comparable with the values of virgin bleaching earth.     

低溶解氧膨胀污泥沉降性能的恢复研究

溶解氧是影响丝状菌污泥膨胀的重要因素之一.以石化废水和啤酒废水为处理对象,对低溶解氧污泥膨胀进行了污泥沉降性能恢复的试验研究.结果表明,在较高的DO浓度下运行,能使膨胀污泥的沉降性能恢复到良好状态,且恢复时间及恢复速率均与污泥膨胀程度呈正相关关系.污泥负荷是影响膨胀污泥沉降性能恢复的因素,在一定低污泥负荷下,通过提高DO浓度并不能使低DO膨胀污泥的沉降性能得到有效恢复.     

溶解氧对一体式膜生物反应器(IMBR)的影响

针对溶解氧(DO)和气水比对IMBR工艺出水效果的影响及能耗问题,从气水比对DO的影响和DO对COD与NH3-N去除效果的影响着手,探讨研究气水比、溶解氧以及污水处理效果之间的最佳工作点。试验结果表明,在ρ(MLSS)分别为4.23,4.09,3.70g/L的运行条件下,MBR的最佳运行气水比相应为35∶1,25∶1,17∶1;溶解氧变化速率随污泥浓度的下降而升高;DO的变化对COD的去除效果并不显著;在高污泥浓度下,DO的质量浓度保持在2.63～4.85mg/L之间时,氨氮的去除率随溶解氧浓度的上升而下降,氨氮去除率达90%以上;但DO浓度过低时,氨氮去除效果不佳。     

人工肝生物反应器中溶解氧浓度动态分布的模型与数值分析

研究了人工肝生物反应器的结构特点,并在对反应器内部液体流动与气液传质规律进行分析的基础上,结合反应器的实际需要,建立了基于一维轴向扩散模型的人工肝专用生物反应器溶解氧浓度动态分布的数学机理模型. 利用有限差分方法对模型离散化求解,得到了流动速度、氧传质系数及细胞耗氧速率对反应器内部溶解氧浓度分布的影响规律. 通过对模型数值解的分析得到了特定条件下反应器内的优化参数为液体流速0.55 mm/s,传质系数0.31 s-1,扩散系数0.02 mm2/s. 最后,通过仿真数据与实测实验的对比验证了该模型的正确性,其平均误差在±5%以内. 本模型的建立在理论上验证了该专用生物反应器可以提供稳定且均匀的溶解氧浓度分布,同时也为下一代新型反应器的优化设计提供了参考数据和理论依据.     

Two-Step Wastewater Treatment: Sequential Ozonation - Aerobic Biodegradation

Ozonation of wastewater from olive related industries has been carried out after dilution with synthetic urban wastewater. The advantages of the application of different acidic and basic cycles during the ozonation process have been shown. Biodegradability of the final effluent measured as the biological oxygen demand to chemical oxygen demand ratio has significantly been increased (100–144% for table olive wastewater and 24–60% for olive oil wastewater). Aerobic biological experiments conducted by using non-acclimated microorganisms confirmed the suitability of the biodegradation after the chemical oxidation pre-treatment. A kinetic model based on a free radical mechanism has been used to simulate experimental results. Both chemical oxygen demand and dissolved ozone concentration profiles are well fitted by the model. The aerobic biodegradation process has been modeled by utilizing the Monod equation.     

Grafting of vinyl monomers by the xanthate method

The removal of oxygen from swollen pulp is very difficult. At least 1–2 h of purging with oxygen-free nitrogen or argon is required as well as efficient mixing and a low concentration of pulp (not higher than 1%). During the grafting reaction, in which the xanthate cellulose is a part of the redox system, the concentration of oxygen falls to zero and stabilizes at this level even if air is purged through the system or a higher rate of stirring is applied. Primary sulfur radicals created in the reaction of the xanthated groups with H₂O₂ are further oxidized by H₂O₂ or by particles of oxygen dissolved in the reaction mixture. The observed increase in reaction caused by an increase in stirring speed is due to the higher rate of diffusion of hydrophobic monomers as well as the diffusion of oxygen to active centers at high stirring speed. The low rate of grafting at lower agitation speeds is caused by agglomeration of monomer molecules to bigger particles and, as a result, decreased diffusion of monomer to active centers. Above 300 rpm, the effect of monomer diffusion diminishes and further increase in conversion is caused only by a higher rate of oxygen diffusion to active centers from reaction mixture or passing gas. However, above a certain level of oxygen, the effect of termination by oxygen prevails and the rate of reaction decreases. Additives increase the conversion in the lower range of agitation speed only. The application of additives and agitation are two equivalent methods, both of which lead to an increase in conversion in the lower range of stirring speed.     

Enhanced production of lovastatin in a bubble column by Aspergillus terreus using a two‐stage feeding strategy

A two‐stage feeding strategy is shown to improve the rate of production of lovastatin by Aspergillus terreus when compared with conventional batch fermentation. The feeding strategy consisted of an initial batch/fed‐batch phase and a semi‐continuous culture dilution phase with retention of pelleted biomass in a slurry bubble column reactor. The batch phase served only to build up the biomass for producing lovastatin, a secondary metabolite that inhibits its own synthesis in the producing microfungus. The semi‐continuous dilution phase provided nutrients to sustain the fungus, but prevented biomass growth by limiting the supply of essential nitrogen. (Synthesis of lovastatin does not require nitrogen.) The preferred pelleted growth morphology that favors lovastatin synthesis was readily obtained and maintained in the 20 L bubble column used. In contrast, a stirred tank fermentation had a substantially lower production of lovastatin because mechanical agitation damaged the fungal pellets. The two‐stage feeding method increased lovastatin production rate by more than 50% in comparison with the conventional batch operation. Rheological data for the fungal broth are presented. Copyright © 2007 Society of Chemical Industry