Showing papers by "Arnold L. Demain published in 2000"

The natural functions of secondary metabolites.

Abstract: Secondary metabolites, including antibiotics, are produced in nature and serve survival functions for the organisms producing them. The antibiotics are a heterogeneous group, the functions of some being related to and others being unrelated to their antimicrobial activities. Secondary metabolites serve: (i) as competitive weapons used against other bacteria, fungi, amoebae, plants, insects, and large animals; (ii) as metal transporting agents; (iii) as agents of symbiosis between microbes and plants, nematodes, insects, and higher animals; (iv) as sexual hormones; and (v) as differentiation effectors. Although antibiotics are not obligatory for sporulation, some secondary metabolites (including antibiotics) stimulate spore formation and inhibit or stimulate germination. Formation of secondary metabolites and spores are regulated by similar factors. This similarity could insure secondary metabolite production during sporulation. Thus the secondary metabolite can: (i) slow down germination of spores until a less competitive environment and more favorable conditions for growth exist; (ii) protect the dormant or initiated spore from consumption by amoebae; or (iii) cleanse the immediate environment of competing microorganisms during germination.

Growth of Streptomyces Hygroscopicus in Rotating-Wall Bioreactor Under Simulated Microgravity Inhibits Rapamycin Production

Abstract: Growth of Streptomyces hygroscopicus under conditions of simulated microgravity in a rotating-wall bioreactor resulted in a pellet form of growth, lowered dry cell weight, and inhibition of rapamycin production. With the addition of Teflon beads to the bioreactor, growth became much less pelleted, dry cell weight increased but rapamycin production was still markedly inhibited. Growth under simulated microgravity favored extracellular production of rapamycin, in contrast to a greater percentage of cell-bound rapamycin observed under normal gravity conditions.

Enhancement of the antifungal activity of rapamycin by the coproduced elaiophylin and nigericin.

Abstract: Streptomyces hygroscopicus ATCC 29253 produces rapamycin, elaiophylin and nigericin. Although elaiophylin has no activity against Candida albicans ATCC 11651, it markedly enhances rapamycin's antifungal activity. Nigericin has only weak activity on its own but it also enhances rapamycin action. Surprisingly, elaiophylin does not enhance nigericin activity on C. albicans.

Method for production of tetanus toxin using media substantially free of animal products

Abstract: The present invention provides a system for the growth of C.tetani and production of Tetanus Toxin for use in formulating Tetanus Toxoid preparations. The system includes growth media that contain significantly reduced levels of meat or dairy by-products using non-animal based products to replace the animal-derived products. Preferred media are substantially free of animal-derived products. Preferred media substantially free of animal-derived products comprise soy as a source of amino acids. The present invention also provides methods for production of Tetanus Toxin by culturing C. tetani in media substantially free of animal-derived products and comprising hydrolyzed soy, glucose and iron.

Bioconversion of compactin to pravastatin by Actinomadura sp. ATCC 55678

Abstract: The screening of known and unidentified actinomycetes revealed three strains which could hydroxylate compactin to pravastatin. The best was a new culture identified as Actinomadura sp. (ATCC 55678). Actinomadura sp. effectively converted compactin to pravastatin. The degree of conversion by cells was 65–78% of compactin added and 65–88% of compactin taken up, depending on the concentration of compactin and duration of the experiment. Increasing the compactin concentration resulted in a higher final pravastatin concentration especially when compactin was added intermittently. The conversion was linear for 16 h. The system required no induction with compactin. The hydroxylase in cell-free extracts of Actinomadura sp. converted compactin to pravastatin. It required NADPH as coenzyme and Mg 2+ as cofactor; Mn 2+ partially replaced Mg 2+ . In contrast to the inducible cytochrome P 450 system of Streptomyces carbophilus which catalyzes the same overall reaction, this constitutive hydroxylase was stimulated by ATP and ascorbic acid and was not inactivated by CO. Actinomadura sp. required vitamins to support its growth. Addition of folic acid, thiamine and cyanocobalamin allowed growth in chemically defined medium. Cells grown in chemically defined medium were as capable of converting compactin to pravastatin as cells grown in complex medium.

Methionine interference in rapamycin production involves repression of demethylrapamycin methyltransferase and S-adenosylmethionine synthetase.

Abstract: In a chemically defined medium, L-methionine decreased production of rapamycin and increased that of demethylrapamycin Growth with L-methionine yielded cells with a lower ability to convert demethylrapamycin to rapamycin and decreased the level of S-adenosylmethionine synthetase and S-adenosylmethionine Thus, methionine represses at least one methyltransferase of rapamycin biosynthesis and S-adenosylmethionine synthetase

Relief from glucose interference in microcin B17 biosynthesis by growth in a rotating-wall bioreactor.

Abstract: Glucose interference in production of microcin B17 by Escherichia coli ZK650 was decreased sevenfold by growth in a ground-based rotating-wall bioreactor operated in the simulated microgravity mode as compared with growth in flasks. When cells were grown in the bioreactor in the normal gravity mode, relief from glucose interference was even more dramatic, amounting to a decrease in glucose interference of over 100-fold.

Immobilized Streptomyces clavuligerus NP1 cells for biotransformation of penicillin G into deacetoxycephalosporin G

Abstract: An investigation was conducted to determine whether immobilized resting cells of Streptomyces clavuligerus NP1, entrapped on a polymeric matrix, are able to perform oxidative ring expansion of benzylpenicillin into deacetoxycephalosporin G by virtue of their deacetoxycephalosporin C synthase ("expandase") activity. Cells entrapped in polyethyleneimine-barium alginate (1.5%) were able to sustain activity for at least four 2-h cycles, whereas free resting cells were inactive after the second cycle. Although entrapped cells exhibited lower oxidative ring expansion activity than free resting cells, immobilization may offer storage stability, recyclability, and operational stability for biotransformation of penicillins to cephalosporins, thus contributing to the development of a biological means for the production of the important industrial intermediate 7-aminodeacetoxycephalosporanic acid.

Edward P. Abraham, cell-free systems and the fungal biosynthesis of beta-lactams.

Abstract: Today much is known about the biology of penicillin and cephalosporin production by fungi including the pathways, the biosynthetic enzymes including some crystal structures, the genes and their cloning, expression, sequencing and chromosomal locations, the regulation of the genes and enzymes and even some intelligent guesses about their evolutionary relationships. The key breakthrough that led to rapid progress in these areas was the subcellular work done by EDWARD P. ABRAHAM and his Oxford colleagues in the early 1970s. With his advice and encouragement, my laboratory was able to prepare reliably active soluble cell-free preparations which were instrumental in elucidation of the biosynthetic pathways in fungi (and also in bacteria) by laboratories throughout the world.

Methode de production de toxine tetanique par utilisation de milieux sensiblement exempts de produits d'origine animale

Abstract: La presente invention concerne un systeme de culture de C. tetani et de production de toxine tetanique s'utilisant dans la formulation de preparations a base d'anatoxine tetanique. Le systeme comprend un milieu de culture contenant des niveaux sensiblement reduits de produits derives de viande ou de produits laitiers, des produits de base d'origine non animale remplacant les produits derives d'origine animale. De preference, les milieux sont sensiblement exempts de produits derives d'origine animale. De preference, les milieux sensiblement exempts de produits derives d'origine animale contiennent du soja comme source d'acides amines. La presente invention concerne egalement des methodes de production de toxine tetanique par mise en culture de C. tetani dans des milieux sensiblement exempts de produits derives d'origine animale et contenant du soja hydrolyse, du glucose et du fer.