Utilization rates of trace halogenated organic compounds in acetate-grown biofilms

Trace concentrations of chlorinated benzenes and chlorinated aliphatics were biotransformed by acetate-supported biofilms, the former under aerobic conditions and the latter under methanogenic conditions. The rates of transformation of the halogenated organic compounds (secondary substrates) differed from that of acetate, the primary substrate; some were higher, some were lower, and some were similar. Factors affecting the relative rates of utilization in multisubstrate systems are not known.     

Sugar cane bagasse as a possible source of fermentable carbohydrates. I. Characterization of bagasse with regard to monosaccharide, hemicellulose, and amino acid composition

Individual monosaccharides present in bagasse hemicellulose were determined using HPLC and other chromatographic procedures. The presence of higher oligomers of the monosaccharides could also be determined. No single procedure can separate and identify all the naturally occurring monosaccharides. The pentosan fraction of bagasse wa successfully hydrolyzed and extracted with 5% (m/v)HCl, and the rate of release of individual monosaccharides was determined. Xylose was the main component in the hydrolyzates, while glucose, arabinose, and galactose present in the side chains of the pentosans were initially released at a fast rate. This treatment resulted in obtaining 229 mg/g xylose (85% of theoretical maximum) and 44 mg/g glucose from bagasse. Only arabinose (2.8 mg/g) and galactose (0.75 mg/g) was also present in detectable quantities. A total of 309 mg monosaccharides were obtained from 1 g of bagasse by this treatment. The results indicated that hydrolysis conditions for specific plant materials depend on the composition of the specific material being utilized. A part of the pentosan fraction (77.1%) was hydrolyzed at a high rate, while 22.9% was more stable and hydrolyzed more slowly. Although 39.8% dry bagasse could be obtained in solution by treatment with dilute alkali, only about 72% of the available hemicelluloses could be extracted in this way if the bagasse was not delignified beforehand. Amino acids and peptides or proteins were also extracted to very much the same with the alkali.     

Control of chicken coccidiosis

Coccidiosis could potentially cause enormous economic loss to the poultry industry, especially in the production of broiler chickens (see Box 1). Losses are currently minimized by chemotherapeutic treatment but the effectiveness of many drugs seems to be declining. In this article, Peter Long and Tom Jeffers discuss the future for coccidial chemotherapy, and the potential for immunological control methods.     

New concepts for rapid yeast settling. II. pH switching with an inert powder

A new technique is outlined for the rapid settling of yeast cells in fermentation media. The technique involved the addition of dense, inert particles (nickel powder) to a yeast suspension (Saccharomyces cerevisiae) at pH 4.5 and a rapid change of pH to 8.0-9.0. When the pH was changed large flocs formed immediately and settled rapidly, leaving a clear supernatant. On returning the pH to 4.5 the flocs were destroyed. This technique gave larger flocs and higher settling rates than the constant pH method, and much lower nickel/yeast ratios were required. Good flocculation also occurred in a fermentation medium. The technique was used to recycle yeast cells to a semicontinuous ethanol fermentation. Application of the technique to this and similar systems is discussed. The factors affecting yeast/inert powder flocculation are also discussed and a model is proposed to explain the observed experimental behavior for flocculation with a rapid change in pH.     

在不同物理化学条件下天花粉蛋白的圆二色性研究

用圆二色谱研究了天花粉蛋白在酸性和碱性溶液中的构象,并观察了在十二烷基磺酸钠(SDS)溶液中天花粉蛋白分子构象的变化,用Chen,Yang与Martinez等人的方法计算了各种条件下天花粉蛋白二级结构含量.结果表明:在很宽广的pH范围内(从pH2到pH12)分子构象基本上是稳定的.但是,在强碱性条件下即pH>12(室温)或pH11.5(40℃)螺旋含量显著减少.在碱性条件下,于250nm附近出现一新的CD带,它的强度与离解的酪氨酸残基个数呈线性关系,说明这一新带主要是由离解的酪氨酸残基产生的.     

湖北郧西范家坪早石炭世四射珊瑚

本文描述了贵阳西北郊探矿厂对面山坡上发现的早二叠世晚期茅口组双切尾虫亚科三叶虫的1新属——棘菲利普虫属(Acanthophillipsia),计4新种:Acanthophillipsia guiyangensis, A. abrota, A. abnormis和A.granurosa,丰富了我国二叠纪三叶虫动物群的资料,对研究二叠纪三叶虫的分类、演化和古生物地理分区都具有一定的意义。     

生物地球化学

生物地球化学是从地球化学学科中分出来的。作为一门新的学科,它的形成是与В.И.Вернадский(1868—1945)的名字分不开的。В.И.Вернадский首次提出了诸如“生物”、“生物圈”等有重大价值的概念。他是世界上头一个重视研究生物的地球作用的科学家。他认为,“生物”概念是活有机体的总和,表现为质量、化学成分和能量。他写道,“生物”首先是一种宇宙现象,并且不可能脱离生物圈,