Gas holdup in an external-loop air-lift fermentor with a contaminated gas distributor

Contamination of the porous-plate gas distributor was observed in an air-lift fermentor used for Aspergillus fumigatus fermentations. Comparisons between gas holdups measured with uncontaminated distributors and the contaminated one showed that the contamination had no effect on gas holdups in water but reduced the holdups in sodium chloride and sodium sulfate solutions, probably due to increased bubble coalescence. A correlation for gas holdups with clean distributors(2) could be used to represent the results for the comtaminated distributor by changing the values used for the characteristic velocities of the electrolyte solutions.     

Structure and properties of enzyme graft copolymers: Temperature effects on HRP immobilization mechanism

The possibility of obtaining immobilized horseradish peroxidase (HRP) materials with K'(m) values close to that of the native enzyme, but with good thermal stability, was investigated. The photochemical reaction was used as the immobilization methodology. Temperature and catalyst concentration were found to be the main parameters able to control the immobilization reaction mechanism more than type of functional monomer, polymer-matrix, and enzyme-polymer ratios. By carrying out the immobilization reaction at 35 degrees C and using either bisacryloylpiperazine (BAP) or hexhydro-1,3,5-triacryloyl-s-triazine (HTsT) as the functional monomer, materials with a good thermal stabilization (the retained activity after 240 min at 60 degrees C was between 65-25%) as well as kinetic constants (0.6-0.8 x 10(-4)M) similar to that of the free enzyme (0.57 x 10(-4)M) were obtained. Since low K'(m) values were obtained also using a high polymer content (pBAP copolymers, 25%; pHTsT copolymers, 30%) and neither limitation to substrate diffusion nor a reduction of the enzyme mobility was found, the enzyme should be linked to the matrix during the last steps of monomer polymerization, and it should have an external disposition with respect to the support.     

Noninferior periodic operation of the biological reactor

The optimal periodic operation of the biological reactor was studied from the standpoint of the two-objective programming problem. The noninferior set with respect to the cell productivity and the conversion of the substrate into the biomass was determined by use of the optimization technique due to Miele. It was shown that the noninferior set was composed in general of the repeated batch branch and the repeated fed-batch branch, which occupy the high-productivity portion and the high-conversion portion of the noninferior set, respectively. However, the latter branch disappears in the case of growth kinetics with no substrate inhibition. In addition, the extreme points of the noninferior set yielding the maximal productivity and the maximal conversion represent such operations that are equivalent to the steady-state operation (chemostat culture) and the batch operation, respectively.     

Aspartate glucan, glycine glucan, and serine glucan for the removal of cobalt and copper from solutions and brines

Aspartate glucan, glycine glucan, and serine glucan obtained by reductive amination of oxalacetic acid, glyoxylic acid, and beta-hydroxypyruvic acid, respectively, with polyglucosamine were tested as chromatographic chelating media. Crosslinked glycine glucan exhibited high capacities for cobalt and copper, even in acidic solutions (pH 2.9). Breakthrough points for 10 mg/L solutions through 6.0 x 0.6 cm columns containing 200 mg of polymer were at 1.8 L for both ions; for 1 mg/L solutions, they were at 4.0 and 12.0 L for cobalt and copper, respectively. Crosslinked glycine glucan could remove microgram amounts of cobalt and copper from fluoride and chloride brines. Cobalt and copper could be separated by elution with 0.25M sulfuric acid.     

慈菇胚囊的发育

被子植物胚囊的发生和发育是有性过程的重要环节,植物只有在胚囊充分发育成熟的情况下,才有卵子与精子的结合,完成受精作用。近年来,有些学者已经证实,胚囊的发育不全或解体往往是引起结籽率降低的原因之一。因此,探讨胚囊的发生和发育对基础理论研究和作物生产有密切关系。     

介绍一个简便易行的遗传学实验——人类P.T.C尝味能力的测定与分析

在遗传课的教学中,验证分离律的方法很多。现行高中生物课本中采用两种自交系杂交的直观实验法,观察后代性状分离的现象。这种方法因受季节的因素限制,在短时间内得不到预期的实验结果,容易与课堂教学脱节,实际在多数中学得不到应有的重视。我们在此介绍一种在实验课能进行的遗传实验——P.T.C尝味能力的测定和分析。     

独角犀小肠粘膜的柱状突起

1960—1978年,我们解剖了雌雄各一例的成年的独角犀(Rhinoceros unicornis),发现小肠粘膜的外观不同于一般哺乳动物. 标本经10％甲醛液固定,常规石腊切片(厚6μm),H.E.染色,做了大体和显微结构的观察.沿系膜附着线剪开全部小肠.在小肠粘膜面上,看不到通常的粘膜皱襞存在,却生长着密集的“肉柱”状突起.这种“肉柱”直径为0.2—0.3cm,高为0.6—1.5cm.表面光滑,质地柔软,彼此无粘连(图1,见封二左下)。至小肠、大肠交界处,“肉柱”消失,代之以稀疏的肠粘膜皱     

尼氏小体染色改良法

尼氏小体又名虎斑,位于神经细胞的胞浆内,用固定液固定后,可见粗细不等的小粒,集聚成大小不同的多角形小块或不规则的长形小体.近年来,用组织化学方法证明,含有大量核糖核酸.在病变或损伤时,尼氏小体减少或消失.尼氏小体的形态,数量及位置在不同的神经细胞和不同的生理状况均有差别. 目前,尼氏小体染色有许多种,但大多数步骤复杂,配制溶液较多.根据尼氏小体的化学性质,它带有较多的负电,能与碱性染料的阳离子结合的原理,我们     

康氏木霉AS3.4001 纤维素酶系的研究

康氏木霉白色变异株AS 3.4001的纤维素酶系经系列分离纯化,获得6个聚丙烯酰安凝胶电泳均一的组分(组分I-V及β一葡萄糖苷酶)。组分1能单独作用于天然纤维素棉花,水解不溶性纤维素,如滤纸、纤维素粉及磷酸膨张纤维素较可溶性纤维素羧甲基纤维素钠 CMC-Na)更为容易,水解产物为纤维二糖及痕迹量葡萄糖。