Plant roots are relatively under-utilized and under-explored sources of secondary metabolites, including pharmaceuticals, agrichemicals, flavors and fragrances. Roots of numerous plant families accumulate and/or synthesize a wide variety of products ranging from the sweet-tasting glycyrrhizic acid of licorice to the emetic and expectorant principles of ipecac . The biosynthesis and mechanisms of accumulation for most of these compounds are poorly understood and the lack of appropriate experimental systems has substantially limited studies on primary and secondary metabolism of roots. This paper reviews recent studies of secondary metabolism in higher plants, with emphasis on the use of organized systems such as the ‘hairy roots’ obtained from transformation of plant cells with . The potential contribution of these novel systems to the production of speciality chemicals through scaled-up cultures is discussed.
The bacterium can produce alcohol more than twice as fast as yeast. The possible large-scale production of ethanol by this organism has been restricted in part because its substrate range is limited to glucose, fructose and sucrose. Recent developments in the genetics and biotechnology of this ethanologen are reviewed.
Enzyme immunoassays play an increasingly important part in the diagnosis of disease and the monitoring of clinical conditions. The sensitivity of enzyme detection systems can be greatly increased by enzyme amplification using the activity of a secondary enzyme system coupled catalytically to the primary label. With a redox cycle based on the cycling of NAD, the signal from the enzyme alkaline phosphatase can be amplified 100–5000 fold giving a detection limit of only 3000 molecules and extending the range of a diagnostic assay into hitherto inaccessible regions.
Major advances in the technology involved in determining protein crystal structures have facilitated several new and existing applications for protein crystallography. Protein crystal growth, the one major bottleneck in this field, has recently received much attention and several new developments hold promise for the future.
Since the first report of immobilized cells in 1966, the area has expanded very rapidly. However, only a few industrial processes are based on immobilized cells probably because profitable processes for large-scale cultivation of freely suspended procaryotic cells already exist. With animal cell culture, however, the advantages of immobilization are more profound and there already exist industrial processes based on immobilized cells. It is also very likely that immobilized animal cells will find an increasing importance in the correction of diseases.
Protein G of is an immunoglobulin-binding protein analogous to protein A of . Because it binds to several animal IgG's and IgG subclasses (including human IgG3) to which protein A does not bind, protein G would be a superior replacement for protein A in many immunochemical applications. To obtain a convenient recombinant source of protein G, genes encoding the protein have been cloned from several independent streptococcal isolates. These cloned genes reveal a structure of protein G which generally resembles protein A, but shows no apparent amino acid sequence homology to protein A in the areas responsible for IgG-binding. The protein is constructed of sets of repeating sequences, the number of which differs in the isolates examined.
Immunoassays have found considerable application in clinical diagnosis, but so far have had surprisingly little impact on food analysis. This situation should now change, with the advent of the first specifically designed, commercial immunoassay kits. The potential of such kits is discussed in the light of current analytical needs, which are constantly expanding due to the influence of legislation and pressure from ‘consumer’ groups. Food immunoassays are easy to perform, sensitive, specific and relatively inexpensive. Their applications include the determination of food additives, meat species, fungal and bacterial contamination, antinutritional factors, pesticide residues and hormones: they thus offer a major new technique to the food analyst.
Microbial physiology is concerned with the interaction of the organism with its environment and the optimum expression of the genetic potential of the organism. The slow advance of microbial physiology has been a limiting factor in the development of the penicillin fermentation and probably of most other fermentations. It is probable that in the factory of the most efficient producers, the average penicillin productivity achieved (units per hour per unit volume) throughout the fermentation is about 40% of the maximum possible. This deficiency shows the scope for improving on the expression of the synthetic ability or the phenotype of a given strain of the organism. Fundamental long-term research on the influence of environmental factors on the expression of the organism's synthetic ability is suggested to elucidate the limitations on the microbial production of antibiotics.