Transformation of Mycobacterium aurum by electroporation: the use of glycine, lysozyme and isonicotinic acid hydrazide in enhancing transformation efficiency

Endoglucanase of Aspergillus niger AS-101 was partially purified by ammonium sulphate fractionation and molecular sieving on Sephadex G-200. The enzyme was found to be unstable on storage, however, it received some protection on the addition of BSA, glycerol or sodium azide. Glycerol also protected the enzyme from inactivation due to freezing and thawing. Studies on the effect of thiol group reagents revealed the involvement of -SH group(s) at the active site of enzyme. The enzyme was a metallo-protein or it required certain metal ions for activation. A variety of modulators such as macroionic compounds and metal ions showed varying effects on the purified endoglucanase.     

Applications of Hydrolytic and Decarboxylating Enzymes in Biotransformations

Peptides, and oligosaccharides and glycosides, can be synthesised by making use of the ‘reverse hydrolytic activity’ of proteases and glycosidases respectively. In applying these enzymes to the practical synthesis of these classes of compound, several factors need to be considered, namely the need to shift the rate-determining step through the use of activated substrates, the need to minimise competing hydrolysis of these and the need to minimise hydrolysis of the products. In spite of these problems, the enzymatic methods have many attractive features, not least amongst which is the absolute control of stereochemistry in acyl transfer and glycosyl transfer respectively.     

Substrate Selectivity in Aspergillus niger KU-8 Acid Phosphatase II Using Phosphoryl Oligosaccharides

The intracellular acid phosphatase II (ACPase II) produced by Aspergillus niger KU-8 preferentially dephosphorylates C-6 phosphate groups rather than C-3 phosphate groups of phosphoryl oligosaccharides. In this study, the kinetic parameters of ACPase II were measured. 3²-phosphoryl maltotriose and 6²-phosphoryl maltotriose, which differ only in the binding position of the phosphate group, were prepared and used as the substrates. The K _m for both substrates were similar. However, the k _cat value for the 6²-phosphoryl maltotriose was about three-fold of that for the 3²-phosphoryl maltotriose.     

Regioselective Enzymatic Hydrolysis of 3',5'-DI-O-Acetylthymidine and Observation of a Surface Effect Due to Polystyrene

The selective enzymatic hydrolysis of 3',5'-di-O-acetylthyidine (1) was studied. The lipases from porcine pancreas and Aspergillus niger, and pig liver esterase, all catalysed selective hydrolysis of the 5'O-acetyl group, but the lipase from Candida cylindracea catalysed selective hydrolysis of the 3'-O-acetyl group. Highest selectivity, leading to essentially pure 3'-O-acetylthymidine, was achieved using porcine pancreatic lipase in dilute solution at pH 7.5. Provision of an artificial interface in the form of polystyrene beads led to a significant increase in the rate of hydrolysis, accompanied by a marked fall in selectivity. Other changes in the hydrolysis conditions, such as raising the concentration of substrate or adding cosolvent, also led to a fall in selectivity.     

Mitochondrial location of pyruvate carboxylase in Aspergillus niger

Pyruvate carboxylase has been found in the mitochondrial fraction of two strains of Aspergillus niger along with the marker enzymes of citrate synthase and cytochrome c oxidase. The location of pyruvate carboxylase in A. nidulans was, however, confirmed to be in the cytosolic fraction. The enzyme from the former sources was dependent upon the presence of acetyl-CoA for full activity; the enzyme from A. nidulans was unaffected by the presence or absence of acetyl-CoA.     

Predicting vegetative inoculum performance to maximize phytase production in solid-state fermentation using response surface methodology

Microbial phytase is used to reduce the environmental loading of phosphorus from animal production facilities. The limiting factors in the use of this enzyme in animal feeds can be overcome by solid-state fermentation (SSF), which is a promising technology for commercial enzyme production with lower production costs. Inoculum quality and the influence of inoculum quality on phytase production are important factors which need in-depth investigation before scaling-up of high-yielding fermentation process. A full factorial experimental design for 240 h with sampling at every 24 h was used to determine the effects of the treatments, inoculum age (plate and liquid culture), media composition and the duration of SSF on the production of fungal biomass and phytase in SSF systems using Aspergillus niger. The optimal treatment combination for maximal phytase production was determined by statistically comparing all treatments at each sampling time. Both 7- and 14-day plate cultures and M1+ medium composition with 72-h-old liquid inoculum treatments resulted in optimal phytase production at 144 h of SSF, which was the shortest duration observed for maximal phytase production. This resulted in maximal phytase production with a mean of 884±121 U/g substrate, while the maximal phytase production observed at 216 h of SSF (mean phytase activity of 1008±121 U/g substrate), with the same treatment combinations, was not statistically significant from that at 144 h of SSF. Phytase production was strongly growth-associated with younger inocula. The significant treatment variables, age of liquid inoculum and the duration of SSF, were used to predict the system response for phytase production using response surface methodology. From the response surface model, the optimal response of the experiment was predicted and the reliability of the prediction was checked with the verification experiment. Journal of Industrial Microbiology & Biotechnology (2001) 26, 161–170. Received 06 June 2000/ Accepted in revised form 14 October 2000     

油菜籽提取物清除活性氧作用研究

自由基是一种带有未成对电子的分子或离子,具有很高的反应活性,可对机体产生毒害,破坏生物大分子,影响细胞活性.如果自由基被中途清除,就可能中断此反应[1].科学研究表明,自由基与免疫、疾病、衰老等许多病理生理现象都有密切的关系.     

卡瓦胡椒及胡椒的RAPD聚类分析

目的：通过RAPD分析搞清楚卡瓦胡椒与胡椒及胡椒属其它近缘野生种的亲缘关系。方法和结果：采用随机引物80条进行筛选,用从80条随机引物中入选的20条引物,对卡瓦胡椒和胡椒属共计28份材料进行RAPD扩增,均能产生清晰的扩增谱带。重复1—2次,结果稳定可靠。20个引物共扩增出170个条带,其中多态性条带有20条,占总扩增条带数的12％。RAPD分析结果显示在相似系数0．36处对28份种质可划分为6个类型,其中卡瓦胡椒被单独聚为一类,说明卡瓦胡椒与胡椒及其它近缘野生种的亲缘关系有一定的距离。     

Microsatellite loci in the stable fly,Stomoxys niger niger (Diptera: Muscidae) on La Réunion Island

Six polymorphic microsatellite markers have been isolated from a microsatellite‐enriched DNA library from the stable fly, Stomoxys niger niger. These loci exhibited five to 10 alleles per locus and an expected heterozygosity ranging from 0.57 to 0.81 in the studied populations from La Réunion Island (Indian Ocean). They should therefore be useful for the study of genetic diversity and population structure of S. niger. In addition, cross‐species amplification of four of these six loci in the closely allied species Stomoxys calcitrans produced interpretable results, two of which would be useful for population biology studies.