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Pierre Germain - One of the best experts on this subject based on the ideXlab platform.
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regulation of Spiramycin synthesis in streptomyces ambofaciens effects of glucose and inorganic phosphate
Applied Microbiology and Biotechnology, 1996Co-Authors: A Lounes, A. Lebrihi, C. Benslimane, Gerard Lefebvre, Pierre GermainAbstract:The production of the 16-membered macrolide antibiotic, Spiramycin, in Streptomyces ambofaciens is inhibited by glucose, 2-deoxyglucose and inorganic phosphate. The role of intracellular ATP content and phosphorylated metabolites as common regulating signals of both glucose and phosphate inhibitory effects is discussed. Two enzymatic targets of the effect of phosphate on Spiramycin biosynthesis were studied. Valine dehydrogenase, the first enzyme of valine catabolism (supplier of aglycone Spiramycin precursors), and alkaline phosphatase, which cleaves phosphorylated intermediates, were repressed in the presence of excess phosphate.
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effect of nitrogen carbon ratio on the specific production rate of Spiramycin by streptomyces ambofaciens
Process Biochemistry, 1996Co-Authors: A Lounes, A. Lebrihi, C. Benslimane, Gerard Lefebvre, Pierre GermainAbstract:Abstract Streptomyces ambofaciens was grown on a synthetic medium with glycerol (10 g litre −1 ) and ammonium (20 m m ) as carbon and nitrogen sources, respectively. Batch fermentation produced a specific production rate of Spiramycin ( q sp ) of 0·3 mg h −1 g −1 DCW. Improvement of Spiramycin production was achieved by fed-batch culture. The strong influence of the initial uptake rates of glycerol ( q gly ) and ammonium ( q NH 4 + ) on the specific production rate of Spiramycin ( q sp ) was demonstrated by conducting several fermentations with continuous feeding of glycerol and ammonium, in different ratios. The specific production rate of Spiramycin was increased 10 fold. A low specific growth rate was also necessary for Spiramycin biosynthesis.
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glycerol effect on Spiramycin production and valine catabolism in streptomyces ambofaciens
Current Microbiology, 1995Co-Authors: A Lounes, A. Lebrihi, C. Benslimane, Gerard Lefebvre, Pierre GermainAbstract:Spiramycin production by Streptomyces ambofaciens in a chemically defined medium, with valine as nitrogen source, was controlled by the nature and the concentration of the carbon source. The production of this antibiotic was better in dextrins than in glycerol-containing medium. The negative effect of glycerol could be attributed in part to an excess of energy and a high specific growth rate. The intracellular ATP content, at the start of Spiramycin production, was twofold higher in glycerol than in dextrin-containing medium. Increasing the initial concentrations of glycerol led to an increase in the specific growth rate and a drop in Spiramycin production. Comparison between glycerol and a protein synthesis inhibitor effects and the use of resting cell systems (RCS) proved that glycerol exerted both inhibitory and repressive actions on Spiramycin production independently from the growth. At the enzymatic level, glycerol interfered with valine catabolism by repressing partially valine dehydrogenase (VDH) and α-ketoisoisovalerate dehydrogenase (KIVDH), generator of Spiramycin aglycone precursors.
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influence of dextrins on the assimilation of yeast extract amino acids in culture of streptomyces ambofaciens producer of Spiramycin
Enzyme and Microbial Technology, 1995Co-Authors: C. Benslimane, A. Lebrihi, G. Lefebvre, A Lounes, Pierre GermainAbstract:Abstract The production of Spiramycin by Streptomyces ambofaciens is controlled by nitrogen and carbon sources present in the complex medium containing dextrins, corn oil, and yeast extract as main substrates. Yeast extract appears to be the most important constituent of the culture medium for the production of Spiramycin. We show that the assimilated fraction varies in the function of medium composition and increases with the exclusion of dextrins. The yeast extract amino acids (32%) can be used as either a carbon or nitrogen source. It was shown that all amino acids were actively used by the strains during the intensive growth phase. The specific production rate of Spiramycin was stimulated by 76% when dextrins were removed from the complex medium containing yeast extract and corn oil as the main compounds. The specific uptake rate of yeast extract amino acids was determined in both cultures (the presence or absence of dextrins). In the presence of dextrins, glutamate, aspartate, asparagine, serine, threonine, alanine, arginine, phenylalanine, histidine, and valine were slowly metabolized, whereas isoleucine, leucine, lysine, glycine, and proline were highly assimilated. When dextrins were removed from the medium, the specific uptake rate of the first group of amino acids was increased, whereas the incorporation of the second group was unaffected. The specific uptake rate of tyrosine, methionine, and tryptophane was reduced. A correlation between an enhancement of Spiramycin production, the consumption of yeast extract, and amino acids and proteolytic activity was established. This was probably due to the supply of energy source and precursors of Spiramycin biosynthesis.
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regulation of valine catabolism by ammonium in streptomyces ambofaciens producer of Spiramycin
Canadian Journal of Microbiology, 1995Co-Authors: A Lounes, A. Lebrihi, C. Benslimane, Gerard Lefebvre, Pierre GermainAbstract:In Streptomyces ambofaciens, valine favored Spiramycin biosynthesis by supplying aglycone precursors. The kinetics of valine consumption and isobutyrate production showed that isobutyrate accumulated in the cell during the growth phase, was excreted in the stationary phase, and then was reassimilated during Spiramycin production. When valine was in excess, its deamination led to high ammonium excretion and to a significant drop in Spiramycin production. We demonstrated that ammonium ions were the cause of the negative effect. Addition of a chelator agent, Ca3(PO4)2, improved Spiramycin production by sixfold. In contrast, addition of ammonium, between 0 and 48 h, severely reduced Spiramycin production. The negative effect of ammonium was reversed by addition of a catabolic intermediate of valine, isobutyrate. In addition to stimulating the specific growth rate, ammonium ions slowed down valine catabolism: the specific valine uptake rate, excretion, and reassimilation of isobutyrate were lowered by the puls...
A. Lebrihi - One of the best experts on this subject based on the ideXlab platform.
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glycosylation steps during Spiramycin biosynthesis in streptomyces ambofaciens involvement of three glycosyltransferases and their interplay with two auxiliary proteins
Antimicrobial Agents and Chemotherapy, 2010Co-Authors: Hoang Chuong Nguyen, A. Lebrihi, Josette Gagnat, Fatma Karray, Thuy Duong Ho HuynhAbstract:Streptomyces ambofaciens synthesizes Spiramycin, a 16-membered macrolide antibiotic used in human medicine. The Spiramycin molecule consists of a polyketide lactone ring (platenolide) synthesized by a type I polyketide synthase, to which three deoxyhexoses (mycaminose, forosamine, and mycarose) are attached successively in this order. These sugars are essential to the antibacterial activity of Spiramycin. We previously identified four genes in the Spiramycin biosynthetic gene cluster predicted to encode glycosyltransferases. We individually deleted each of these four genes and showed that three of them were required for Spiramycin biosynthesis. The role of each of the three glycosyltransferases in Spiramycin biosynthesis was determined by identifying the biosynthetic intermediates accumulated by the corresponding mutant strains. This led to the identification of the glycosyltransferase responsible for the attachment of each of the three sugars. Moreover, two genes encoding putative glycosyltransferase auxiliary proteins were also identified in the Spiramycin biosynthetic gene cluster. When these two genes were deleted, one of them was found to be dispensable for Spiramycin biosynthesis. However, analysis of the biosynthetic intermediates accumulated by mutant strains devoid of each of the auxiliary proteins (or of both of them), together with complementation experiments, revealed the interplay of glycosyltransferases with the auxiliary proteins. One of the auxiliary proteins interacted efficiently with the two glycosyltransferases transferring mycaminose and forosamine while the other auxiliary protein interacted only with the mycaminosyltransferase.
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regulation of Spiramycin synthesis in streptomyces ambofaciens effects of glucose and inorganic phosphate
Applied Microbiology and Biotechnology, 1996Co-Authors: A Lounes, A. Lebrihi, C. Benslimane, Gerard Lefebvre, Pierre GermainAbstract:The production of the 16-membered macrolide antibiotic, Spiramycin, in Streptomyces ambofaciens is inhibited by glucose, 2-deoxyglucose and inorganic phosphate. The role of intracellular ATP content and phosphorylated metabolites as common regulating signals of both glucose and phosphate inhibitory effects is discussed. Two enzymatic targets of the effect of phosphate on Spiramycin biosynthesis were studied. Valine dehydrogenase, the first enzyme of valine catabolism (supplier of aglycone Spiramycin precursors), and alkaline phosphatase, which cleaves phosphorylated intermediates, were repressed in the presence of excess phosphate.
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effect of nitrogen carbon ratio on the specific production rate of Spiramycin by streptomyces ambofaciens
Process Biochemistry, 1996Co-Authors: A Lounes, A. Lebrihi, C. Benslimane, Gerard Lefebvre, Pierre GermainAbstract:Abstract Streptomyces ambofaciens was grown on a synthetic medium with glycerol (10 g litre −1 ) and ammonium (20 m m ) as carbon and nitrogen sources, respectively. Batch fermentation produced a specific production rate of Spiramycin ( q sp ) of 0·3 mg h −1 g −1 DCW. Improvement of Spiramycin production was achieved by fed-batch culture. The strong influence of the initial uptake rates of glycerol ( q gly ) and ammonium ( q NH 4 + ) on the specific production rate of Spiramycin ( q sp ) was demonstrated by conducting several fermentations with continuous feeding of glycerol and ammonium, in different ratios. The specific production rate of Spiramycin was increased 10 fold. A low specific growth rate was also necessary for Spiramycin biosynthesis.
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glycerol effect on Spiramycin production and valine catabolism in streptomyces ambofaciens
Current Microbiology, 1995Co-Authors: A Lounes, A. Lebrihi, C. Benslimane, Gerard Lefebvre, Pierre GermainAbstract:Spiramycin production by Streptomyces ambofaciens in a chemically defined medium, with valine as nitrogen source, was controlled by the nature and the concentration of the carbon source. The production of this antibiotic was better in dextrins than in glycerol-containing medium. The negative effect of glycerol could be attributed in part to an excess of energy and a high specific growth rate. The intracellular ATP content, at the start of Spiramycin production, was twofold higher in glycerol than in dextrin-containing medium. Increasing the initial concentrations of glycerol led to an increase in the specific growth rate and a drop in Spiramycin production. Comparison between glycerol and a protein synthesis inhibitor effects and the use of resting cell systems (RCS) proved that glycerol exerted both inhibitory and repressive actions on Spiramycin production independently from the growth. At the enzymatic level, glycerol interfered with valine catabolism by repressing partially valine dehydrogenase (VDH) and α-ketoisoisovalerate dehydrogenase (KIVDH), generator of Spiramycin aglycone precursors.
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influence of dextrins on the assimilation of yeast extract amino acids in culture of streptomyces ambofaciens producer of Spiramycin
Enzyme and Microbial Technology, 1995Co-Authors: C. Benslimane, A. Lebrihi, G. Lefebvre, A Lounes, Pierre GermainAbstract:Abstract The production of Spiramycin by Streptomyces ambofaciens is controlled by nitrogen and carbon sources present in the complex medium containing dextrins, corn oil, and yeast extract as main substrates. Yeast extract appears to be the most important constituent of the culture medium for the production of Spiramycin. We show that the assimilated fraction varies in the function of medium composition and increases with the exclusion of dextrins. The yeast extract amino acids (32%) can be used as either a carbon or nitrogen source. It was shown that all amino acids were actively used by the strains during the intensive growth phase. The specific production rate of Spiramycin was stimulated by 76% when dextrins were removed from the complex medium containing yeast extract and corn oil as the main compounds. The specific uptake rate of yeast extract amino acids was determined in both cultures (the presence or absence of dextrins). In the presence of dextrins, glutamate, aspartate, asparagine, serine, threonine, alanine, arginine, phenylalanine, histidine, and valine were slowly metabolized, whereas isoleucine, leucine, lysine, glycine, and proline were highly assimilated. When dextrins were removed from the medium, the specific uptake rate of the first group of amino acids was increased, whereas the incorporation of the second group was unaffected. The specific uptake rate of tyrosine, methionine, and tryptophane was reduced. A correlation between an enhancement of Spiramycin production, the consumption of yeast extract, and amino acids and proteolytic activity was established. This was probably due to the supply of energy source and precursors of Spiramycin biosynthesis.
Gerard Lefebvre - One of the best experts on this subject based on the ideXlab platform.
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regulation of Spiramycin synthesis in streptomyces ambofaciens effects of glucose and inorganic phosphate
Applied Microbiology and Biotechnology, 1996Co-Authors: A Lounes, A. Lebrihi, C. Benslimane, Gerard Lefebvre, Pierre GermainAbstract:The production of the 16-membered macrolide antibiotic, Spiramycin, in Streptomyces ambofaciens is inhibited by glucose, 2-deoxyglucose and inorganic phosphate. The role of intracellular ATP content and phosphorylated metabolites as common regulating signals of both glucose and phosphate inhibitory effects is discussed. Two enzymatic targets of the effect of phosphate on Spiramycin biosynthesis were studied. Valine dehydrogenase, the first enzyme of valine catabolism (supplier of aglycone Spiramycin precursors), and alkaline phosphatase, which cleaves phosphorylated intermediates, were repressed in the presence of excess phosphate.
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effect of nitrogen carbon ratio on the specific production rate of Spiramycin by streptomyces ambofaciens
Process Biochemistry, 1996Co-Authors: A Lounes, A. Lebrihi, C. Benslimane, Gerard Lefebvre, Pierre GermainAbstract:Abstract Streptomyces ambofaciens was grown on a synthetic medium with glycerol (10 g litre −1 ) and ammonium (20 m m ) as carbon and nitrogen sources, respectively. Batch fermentation produced a specific production rate of Spiramycin ( q sp ) of 0·3 mg h −1 g −1 DCW. Improvement of Spiramycin production was achieved by fed-batch culture. The strong influence of the initial uptake rates of glycerol ( q gly ) and ammonium ( q NH 4 + ) on the specific production rate of Spiramycin ( q sp ) was demonstrated by conducting several fermentations with continuous feeding of glycerol and ammonium, in different ratios. The specific production rate of Spiramycin was increased 10 fold. A low specific growth rate was also necessary for Spiramycin biosynthesis.
-
glycerol effect on Spiramycin production and valine catabolism in streptomyces ambofaciens
Current Microbiology, 1995Co-Authors: A Lounes, A. Lebrihi, C. Benslimane, Gerard Lefebvre, Pierre GermainAbstract:Spiramycin production by Streptomyces ambofaciens in a chemically defined medium, with valine as nitrogen source, was controlled by the nature and the concentration of the carbon source. The production of this antibiotic was better in dextrins than in glycerol-containing medium. The negative effect of glycerol could be attributed in part to an excess of energy and a high specific growth rate. The intracellular ATP content, at the start of Spiramycin production, was twofold higher in glycerol than in dextrin-containing medium. Increasing the initial concentrations of glycerol led to an increase in the specific growth rate and a drop in Spiramycin production. Comparison between glycerol and a protein synthesis inhibitor effects and the use of resting cell systems (RCS) proved that glycerol exerted both inhibitory and repressive actions on Spiramycin production independently from the growth. At the enzymatic level, glycerol interfered with valine catabolism by repressing partially valine dehydrogenase (VDH) and α-ketoisoisovalerate dehydrogenase (KIVDH), generator of Spiramycin aglycone precursors.
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regulation of valine catabolism by ammonium in streptomyces ambofaciens producer of Spiramycin
Canadian Journal of Microbiology, 1995Co-Authors: A Lounes, A. Lebrihi, C. Benslimane, Gerard Lefebvre, Pierre GermainAbstract:In Streptomyces ambofaciens, valine favored Spiramycin biosynthesis by supplying aglycone precursors. The kinetics of valine consumption and isobutyrate production showed that isobutyrate accumulated in the cell during the growth phase, was excreted in the stationary phase, and then was reassimilated during Spiramycin production. When valine was in excess, its deamination led to high ammonium excretion and to a significant drop in Spiramycin production. We demonstrated that ammonium ions were the cause of the negative effect. Addition of a chelator agent, Ca3(PO4)2, improved Spiramycin production by sixfold. In contrast, addition of ammonium, between 0 and 48 h, severely reduced Spiramycin production. The negative effect of ammonium was reversed by addition of a catabolic intermediate of valine, isobutyrate. In addition to stimulating the specific growth rate, ammonium ions slowed down valine catabolism: the specific valine uptake rate, excretion, and reassimilation of isobutyrate were lowered by the puls...
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influence of growth rate and precursor availability on Spiramycin production in streptomyces ambofaciens
Canadian Journal of Microbiology, 1995Co-Authors: Sophie Untrautaghian, A. Lebrihi, Pierre Germain, Gerard LefebvreAbstract:The development of a culture medium in which the growth rate was limited by initial phosphate concentration permitted Spiramycin production during the growth phase. The influence of the growth rate...
Fatma Karray - One of the best experts on this subject based on the ideXlab platform.
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Regulation of the biosynthesis of the macrolide antibiotic Spiramycin in Streptomyces ambofaciens.
Journal of Bacteriology, 2010Co-Authors: Fatma Karray, Emmanuelle Darbon, Hoang Chuong Nguyen, Josette GagnatAbstract:Streptomyces ambofaciens synthesizes the macrolide antibiotic Spiramycin. The biosynthetic gene cluster for Spiramycin has been characterized for S. ambofaciens. In addition to the regulatory gene srmR (srm22), previously identified (M. Geistlich et al., Mol. Microbiol. 6:2019-2029, 1992), three putative regulatory genes had been identified by sequence analysis. Gene expression analysis and gene inactivation experiments showed that only one of these three genes, srm40, plays a major role in the regulation of Spiramycin biosynthesis. The disruption of srm22 or srm40 eliminated Spiramycin production while their overexpression increased Spiramycin production. Expression analysis was performed by reverse transcription-PCR (RT-PCR) for all the genes of the cluster in the wild-type strain and in the srm22 (srmR) and srm40 deletion mutants. The results from the expression analysis, together with the ones from the complementation experiments, indicated that Srm22 is required for srm40 expression, Srm40 being a pathway-specific activator that controls most, if not all, of the Spiramycin biosynthetic genes.
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glycosylation steps during Spiramycin biosynthesis in streptomyces ambofaciens involvement of three glycosyltransferases and their interplay with two auxiliary proteins
Antimicrobial Agents and Chemotherapy, 2010Co-Authors: Hoang Chuong Nguyen, A. Lebrihi, Josette Gagnat, Fatma Karray, Thuy Duong Ho HuynhAbstract:Streptomyces ambofaciens synthesizes Spiramycin, a 16-membered macrolide antibiotic used in human medicine. The Spiramycin molecule consists of a polyketide lactone ring (platenolide) synthesized by a type I polyketide synthase, to which three deoxyhexoses (mycaminose, forosamine, and mycarose) are attached successively in this order. These sugars are essential to the antibacterial activity of Spiramycin. We previously identified four genes in the Spiramycin biosynthetic gene cluster predicted to encode glycosyltransferases. We individually deleted each of these four genes and showed that three of them were required for Spiramycin biosynthesis. The role of each of the three glycosyltransferases in Spiramycin biosynthesis was determined by identifying the biosynthetic intermediates accumulated by the corresponding mutant strains. This led to the identification of the glycosyltransferase responsible for the attachment of each of the three sugars. Moreover, two genes encoding putative glycosyltransferase auxiliary proteins were also identified in the Spiramycin biosynthetic gene cluster. When these two genes were deleted, one of them was found to be dispensable for Spiramycin biosynthesis. However, analysis of the biosynthetic intermediates accumulated by mutant strains devoid of each of the auxiliary proteins (or of both of them), together with complementation experiments, revealed the interplay of glycosyltransferases with the auxiliary proteins. One of the auxiliary proteins interacted efficiently with the two glycosyltransferases transferring mycaminose and forosamine while the other auxiliary protein interacted only with the mycaminosyltransferase.
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Organization of the biosynthetic gene cluster for the macrolide antibiotic Spiramycin in Streptomyces ambofaciens.
Microbiology, 2007Co-Authors: Fatma Karray, Josette Gagnat, Karine Tuphile, Emmanuelle Darbon, Nathalie Oestreicher, Hélène Dominguez, Marie-hélène Blondelet-rouault, Claude GerbaudAbstract:Spiramycin, a 16-membered macrolide antibiotic used in human medicine, is produced by Streptomyces ambofaciens; it comprises a polyketide lactone, platenolide, to which three deoxyhexose sugars are attached. In order to characterize the gene cluster governing the biosynthesis of Spiramycin, several overlapping cosmids were isolated from an S. ambofaciens gene library, by hybridization with various probes (Spiramycin resistance or biosynthetic genes, tylosin biosynthetic genes), and the sequences of their inserts were determined. Sequence analysis showed that the Spiramycin biosynthetic gene cluster spanned a region of over 85 kb of contiguous DNA. In addition to the five previously described genes that encode the type I polyketide synthase involved in platenolide biosynthesis, 45 other genes have been identified. It was possible to propose a function for most of the inferred proteins in Spiramycin biosynthesis, in its regulation, in resistance to the produced antibiotic or in the provision of extender units for the polyketide synthase. Two of these genes, predicted to be involved in deoxysugar biosynthesis, were inactivated by gene replacement, and the resulting mutants were unable to produce Spiramycin, thus confirming their involvement in Spiramycin biosynthesis. This work reveals the main features of Spiramycin biosynthesis and constitutes a first step towards a detailed molecular analysis of the production of this medically important antibiotic.
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etude de la biosynthese de l antibiotique Spiramycine par streptomyces ambofaciens
2005Co-Authors: Fatma KarrayAbstract:Streptomyces ambofaciens synthesizes the 16-membered macrolide antibiotic Spiramycin. The biosynthetic gene cluster for Spiramycin has been characterized in S. Ambofaciens. Sequence analysis of a region of more than 100 kb spanning the entire cluster revealed the presence of 50 genes, 41 of them being most probably involved in Spiramycin biosynthesis, its regulation or resistance to the antibiotic. In order to study the role of the gene products in Spiramycin biosynthesis, we constructed strains in which some genes were inactivated by in-frame deletion. For this purpose, we developed cassettes that can be easily excised by site-specific recombination. Two regulatory genes, srmR and srmS, were identified in the biosynthetic gene cluster. The disruption of each of these two regulatory genes eliminated Spiramycin production while the over-expression of each of them increased three fold the level of Spiramycin production. Expression analysis by RT-PCR for all the genes of the cluster in the wild type strain, in srmR and srmS deletion mutants and in the srmR, srmS double deletion mutant was performed. These results, together with complementation experiments, indicated that SrmR is required for srmS expression, SrmS being a pathway-specific activator that controls most of the Spiramycin biosynthetic genes. Spiramycin is normally produced as a mixture of Spiramycin I, II and III. Spiramycin I is the most active form of the antibiotic. We identified and inactivated the gene encoding the acetyltransferase responsible for the production of Spiramycin II and III. The level of production of this mutant strain was further increased by over-expression of the regulatory gene srmR.
C. Benslimane - One of the best experts on this subject based on the ideXlab platform.
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regulation of Spiramycin synthesis in streptomyces ambofaciens effects of glucose and inorganic phosphate
Applied Microbiology and Biotechnology, 1996Co-Authors: A Lounes, A. Lebrihi, C. Benslimane, Gerard Lefebvre, Pierre GermainAbstract:The production of the 16-membered macrolide antibiotic, Spiramycin, in Streptomyces ambofaciens is inhibited by glucose, 2-deoxyglucose and inorganic phosphate. The role of intracellular ATP content and phosphorylated metabolites as common regulating signals of both glucose and phosphate inhibitory effects is discussed. Two enzymatic targets of the effect of phosphate on Spiramycin biosynthesis were studied. Valine dehydrogenase, the first enzyme of valine catabolism (supplier of aglycone Spiramycin precursors), and alkaline phosphatase, which cleaves phosphorylated intermediates, were repressed in the presence of excess phosphate.
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effect of nitrogen carbon ratio on the specific production rate of Spiramycin by streptomyces ambofaciens
Process Biochemistry, 1996Co-Authors: A Lounes, A. Lebrihi, C. Benslimane, Gerard Lefebvre, Pierre GermainAbstract:Abstract Streptomyces ambofaciens was grown on a synthetic medium with glycerol (10 g litre −1 ) and ammonium (20 m m ) as carbon and nitrogen sources, respectively. Batch fermentation produced a specific production rate of Spiramycin ( q sp ) of 0·3 mg h −1 g −1 DCW. Improvement of Spiramycin production was achieved by fed-batch culture. The strong influence of the initial uptake rates of glycerol ( q gly ) and ammonium ( q NH 4 + ) on the specific production rate of Spiramycin ( q sp ) was demonstrated by conducting several fermentations with continuous feeding of glycerol and ammonium, in different ratios. The specific production rate of Spiramycin was increased 10 fold. A low specific growth rate was also necessary for Spiramycin biosynthesis.
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etude physiologique de streptomyces ambofaciens producteur de la Spiramycine en milieu complexe effet de la source de carbone sur la consommation des acides amines et des acylglycerols
1996Co-Authors: C. BenslimaneAbstract:L’amelioration rationnelle des procedes de fermentation passe par une meilleure comprehension de la physiologie des micro-organismes d'interet industriel. L’etude physiologique de Streptomyces ambofaciens producteur de la Spiramycine, un macrolide a 16 membres, est largement etudiee en milieux synthetiques. L’utilisation de milieux tres complexes, de type industriel et de composition souvent variable, limite ces etudes physiologiques dans ces conditions. Pour mieux comprendre le comportement cinetique de ce micro-organisme dans de tels milieux, nous avons aborde une etude du metabolisme initial des acides amines, des lipides (acylglycerols) et de leur interactions dans des milieux complexes de type industriel contenant comme principaux substrats, des dextrines, de l'extrait de levure et de l'huile de mais. Des etudes preliminaires en fioles d'erlenmeyer ont permis de maitriser les conditions permettant une reproductibilite des fermentations et une production de Spiramycine satisfaisantes. Les interactions entre les principaux substrats du milieu de culture et leur incidence sur la production de Spiramycine ont ete etudiees. La presence de dextrines reduit les activites lipolytiques et proteolytiques, l'assimilation des acylglycerols, des acides gras libres a longues chaines, de certains acides amines et la production de Spiramycine. L’evolution des flux initiaux des differents substrats au cours des croissances est presentee. L’evolution de la constitution et de la mobilisation des reserves energetiques (glycogene, trehalose, lipides totaux et triacylglyerols) est analysee. Des hypotheses expliquant les relations entre composition en lipides de S. ambofaciens, transport des acides amines et production de Spiramycine sont proposees
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glycerol effect on Spiramycin production and valine catabolism in streptomyces ambofaciens
Current Microbiology, 1995Co-Authors: A Lounes, A. Lebrihi, C. Benslimane, Gerard Lefebvre, Pierre GermainAbstract:Spiramycin production by Streptomyces ambofaciens in a chemically defined medium, with valine as nitrogen source, was controlled by the nature and the concentration of the carbon source. The production of this antibiotic was better in dextrins than in glycerol-containing medium. The negative effect of glycerol could be attributed in part to an excess of energy and a high specific growth rate. The intracellular ATP content, at the start of Spiramycin production, was twofold higher in glycerol than in dextrin-containing medium. Increasing the initial concentrations of glycerol led to an increase in the specific growth rate and a drop in Spiramycin production. Comparison between glycerol and a protein synthesis inhibitor effects and the use of resting cell systems (RCS) proved that glycerol exerted both inhibitory and repressive actions on Spiramycin production independently from the growth. At the enzymatic level, glycerol interfered with valine catabolism by repressing partially valine dehydrogenase (VDH) and α-ketoisoisovalerate dehydrogenase (KIVDH), generator of Spiramycin aglycone precursors.
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influence of dextrins on the assimilation of yeast extract amino acids in culture of streptomyces ambofaciens producer of Spiramycin
Enzyme and Microbial Technology, 1995Co-Authors: C. Benslimane, A. Lebrihi, G. Lefebvre, A Lounes, Pierre GermainAbstract:Abstract The production of Spiramycin by Streptomyces ambofaciens is controlled by nitrogen and carbon sources present in the complex medium containing dextrins, corn oil, and yeast extract as main substrates. Yeast extract appears to be the most important constituent of the culture medium for the production of Spiramycin. We show that the assimilated fraction varies in the function of medium composition and increases with the exclusion of dextrins. The yeast extract amino acids (32%) can be used as either a carbon or nitrogen source. It was shown that all amino acids were actively used by the strains during the intensive growth phase. The specific production rate of Spiramycin was stimulated by 76% when dextrins were removed from the complex medium containing yeast extract and corn oil as the main compounds. The specific uptake rate of yeast extract amino acids was determined in both cultures (the presence or absence of dextrins). In the presence of dextrins, glutamate, aspartate, asparagine, serine, threonine, alanine, arginine, phenylalanine, histidine, and valine were slowly metabolized, whereas isoleucine, leucine, lysine, glycine, and proline were highly assimilated. When dextrins were removed from the medium, the specific uptake rate of the first group of amino acids was increased, whereas the incorporation of the second group was unaffected. The specific uptake rate of tyrosine, methionine, and tryptophane was reduced. A correlation between an enhancement of Spiramycin production, the consumption of yeast extract, and amino acids and proteolytic activity was established. This was probably due to the supply of energy source and precursors of Spiramycin biosynthesis.
