pH对L-天冬酰胺酶发酵的影响及其控制

pH对大肠杆菌L-天冬酰胺酶的产生有很大的影响.通过对不同缓冲体系试验和对摇瓶发酵过程pH变化的分析,了解摇瓶发酵过程中pH对L-天冬酰胺酶合成的影响.采用流加磷酸自控L-天冬酰胺酶发酵过程的pH,可延长发酵周期,有效地防止菌体的过早自溶,大大促进L-天冬酰胺酶的合成,较分批发酵提高产酶83%,达到110 u/mL.发酵动力学特性分析表明,该发酵方式L-天冬酰胺酶的合成与菌体生长不相关,控制比生长速率μ为0.15～0.30 h-1,均有利于L-天冬酰胺酶的合成,可使比产酶速率的最大值Qpmax达到3 922 u/(g h).     

厌氧及二级交互间歇曝气工艺条件下微生物生长动力学特性

在厌氧及二级交互间歇曝气工艺条件(CHBNR,Cui-Hong Biological Nutirents Removal Process)和厌氧-好氧工艺条件下(ASP,Activated Sludge Process)分别确定微生物生长动力学系数,并比较评价了厌氧及二级交互间歇曝气工艺的微生物生长动力学特性.通过试验得出在厌氧及二级交间歇曝气条件下Y(微生物增长系数)、Kd(微生物衰减系数)、K(微生物最大相对增长速度)、Ks(饱和常数)分别为0.200,0.055 d-1,3.12 d-1,38.3 mg/L.厌氧及好氧条件下Y,Kd,K,Ks分别为0.253,0.092 d-1,2.22 d-1,31.7 mg/L.这说明厌氧及二级交互间歇曝气工艺,虽然消耗很多的外部有机物质,但维持自身所需的能源少,相对增长速度小,污泥的生产量少,因而,废弃的污泥量会减少,处理污泥费用降低.     

京杭运河镇江-无锡段沉积物不同粒径颗粒物Cd的分布、吸附及影响因素

城市运河受水动力扰动强烈,沉积物再悬浮频繁并易于导致颗粒物发生粒径分选,从而影响各类污染物质的迁移转化过程。研究在京杭运河的镇江-无锡段设置3个采样点J1、J2和J3,对表层沉积物镉（Cd）的含量进行分析。以J2采样点为代表,采用湿沉降法对沉积物进行粒级分选,分离出50-150 μm、30?50 μm、10?30 μm、5-10 μm和<5 μm等5组不同粒径颗粒物,以此为基础对各粒径组颗粒物Cd的含量及相关理化指标有机质（OM）、铁（Fe）、铝（Al）进行了测定,并对它们的Cd的吸附动力学、等温吸附特征进行了研究,分析了理化性质对吸附特征参数的影响。结果表明：镇江-无锡段沉积物Cd的含量范围为0.61-0.95 mg/kg,为太湖背景值的2-3倍;J2采样点沉积物Cd含量随颗粒物粒径的减少有增加的趋势,其中<5 μm粒径颗粒物Cd的含量为1.67 mg/kg;Cd的吸附容量和吸附能力随着颗粒物粒径的减小而增加,OM、铁氧化物和铝氧化物在不同粒径颗粒物上的分异可能是导致它们Cd吸附性能差异的重要原因所在。     

Gas-solid reduction kinetic model of MgO-fluxed pellets

The reduction process of MgO-fluxed pellets was investigated and compared with traditional acidic pellets in this paper. Based on the piston flow concept and experimental data, a kinetic model fitting for the gas-solid phase reduction of pellets in tubular reactors (blast furnace, BF) was built up, and the equations of reduction reaction rate were given for pellets. A series of reduction experiments of pellets were carried out to verify the model. As a result, the experimental data and calculated result were fitted well. Therefore, this model can well describe the gas-solid phase reduction process and calculate the reduction reaction rate of pellets. Besides, it can give a better explanation that the reduction reaction rate (reducibility) of MgO-fluxed pellets is better than that of traditional acidic pellets in BF.     

He-Ne激光诱变选育产氢拜氏梭菌

采用He-Ne激光器对拜氏梭菌(Clostridium beijerinckii)进行激光诱变育种,对激光诱变参数进行优化,结果表明,随着照射剂量的变化,存活率随之变化,输出功率和辐射时间均由正突变率决定。在最佳照射条件(19 m W,16 min)下,得到稳定的阳性突变株BH4。在初始葡萄糖浓度为10 g/L的分批培养中,突变株每克葡萄糖的最终产氢量为260. 7 m L,比野生菌高出28. 9%。酶测定显示,诱变后氢化酶活性增加,这可能有助于提高产氢量。此外,研究了分批培养物中突变体BH4及其野生菌的动力学,其初始葡萄糖浓度为1～10 g/L。动力学参数还表明,突变菌比其野生菌具有更强的产氢能力。说明该He-Ne激光诱变育种技术可以在产氢微生物领域中应用。     

肠膜明串珠菌CICC-21725产右旋糖酐的发酵动力学

研究肠膜明串珠菌CICC-21725发酵产右旋糖酐过程。根据菌体生长量、蔗糖浓度和右旋糖酐产率与发酵时间的关系,采用Logistic Law方程和Luedeking-Piret方程,建立肠膜明串珠菌CICC-21725菌体生长动力学模型、产物合成动力学模型和底物消耗动力学模型。运用Matlab 7.0软件对实验数据拟合,获得模型参数。用红外光谱和核磁氢谱、碳谱对菌体发酵产物进行结构表征。结果表明:所建立的动力学模型的预测值与实验值吻合较好,拟合模型的相关系数分别为0.994 2、0.996 9和0.991 2,模型能较好的预测肠膜明串珠菌CICC-21725发酵产右旋糖酐的动力学过程。肠膜明串珠菌CICC-21725发酵过程中右旋糖酐的合成属于生长偶联型。红外光谱及核磁共振光谱结果表明肠膜明串珠菌的发酵产物是由为α-(1,6)糖苷键连接的直链α型右旋糖酐。     

β-环糊精交联聚合物吸附水中亚甲蓝的机理

以氧化镁为致孔剂,利用环氧氯丙烷交联β-环糊精,合成多孔β-环糊精交联聚合物(β-CDP).考察β-CDP对亚甲蓝(MB)的吸附动力学、热力学讨论吸附的作用机理,并考察pH值、MB的初始质量浓度、吸附剂的投入量、吸附时间及吸附温度对β-CDP吸附MB的影响.结果表明:在室温下,水体的pH值为6.54,MB初始质量浓度为40 mg·L^-1,吸附剂投入量为0.6 g·L^-1,β-CDP的最大吸附量为62.6 mg·L^-1;吸附符合准二级吸附动力学模型和Freundlich等温吸附模型;结合颗粒内扩散模型,以及吸附热力学数据ΔH为20.50 kJ·mol^-1,ΔG为-6.1~-7.5 kJ·mol^-1,可得该吸附为异质表面的多因素联合控制物理吸附.     

Staged reaction kinetics and characteristics of iron oxide direct reduction by carbon

Staged reduction kinetics and characteristics of iron oxide direct reduction by carbon were studied in this work. The characteristics were investigated by simultaneous thermogravimetric analysis, X-ray diffraction (XRD), and quadrupole mass spectrometry. The kinetics parameters of the reduction stages were obtained by isoconversional (model-free) methods. Three stages in the reduction are Fe₂O₃→Fe₃O₄, Fe₃O₄→FeO, and FeO→Fe, which start at 912 K, 1255 K, and 1397 K, respectively. The CO content in the evolved gas is lower than the CO₂ content in the Fe₂O₃→Fe₃O₄ stage but is substantially greater than the CO₂ contents in the Fe₃O₄→FeO and FeO→Fe stages, where gasification starts at approximately 1205 K. The activation energy (E) of the three stages are 126–309 kJ/mol, 628 kJ/mol, and 648 kJ/mol, respectively. The restrictive step of the total reduction is FeO→Fe. If the rate of the total reduction is to be improved, the rate of the FeO→Fe reduction should be improved first. The activation energy of the first stage is much lower than those of the latter two stages because of carbon gasification. Carbon gasification and Fe_xO_y reduction by CO, which are the restrictive step in the last two stages, require further study.     

Kinetic study of austenite formation during continuous heating of unalloyed ductile iron

The austenite formation kinetics in unalloyed cast ductile iron was studied on the basis of dilatometry measurements, and Avrami's equation was used to estimate the material's kinetic parameters. A continuous heating transformation diagram was constructed using heating rates in the range of 0.06 to 0.83℃·s-1. As the heating rate was augmented, the critical temperatures, A_c1 and A_α, as well as the intercritical range, which was evaluated as the difference between the critical temperatures, ΔT=A_α - A_c1, increased. At a low heating rate, the kinetics of austenite formation was slow as a consequence of the iron's silicon content. The effect of heating rate on k and n, the kinetic parameters of Avrami's equation, was also determined. Parameter n, which is associated with nucleation sites and growth geometry, decreased with an increase in heating rate. In addition, parameter k increased with the increase of heating rate, suggesting that the nucleation and growth rates are carbon- and silicon-diffusion controlled during austenite formation under continuous heating.     

低温燃烧法合成纳米二氧化钛粉体研究

采用一种简便、快速、低温的溶胶凝胶自蔓延燃烧法制备了纳米TiO2粉体颗粒.从柠檬酸络合反应的机理阐释了纳米TiO2粒子的形成过程.通过热综合分析、X射线衍射和透射电镜分析探讨了金属离子与柠檬酸的摩尔比和溶液杂质离子的存在对TiO2粉体颗粒物相组成及粉末晶粒尺寸大小的影响.本实验制备了粒径为40～90 nm分散性较好的球形状TiO2纳米颗粒.X射线衍射结果表明,当摩尔比为0.5时,自燃合成产物中金红石相的质量分数达到91%.