RESUMO
A full-factorial experimental design at three levels with two independent variables, carrageenan concentration (1.0, 1.5, and 2.0%) and potassium chloride concentration (0.3, 0.7, and 1.1 M) was studied in order to analyze the effect of both factors on the antibiotic production of K-carrageenan-immobilized mycelia of Streptomyces aureofaciens. The response surfaces obtained have indicated that both carrageenan and potassium chloride concentrations have a pronounced effect on the yield of chlortetracycline (CTC) and tetracycline (TC) produced by S. aureofaciens. By exclusively varying the immobilization conditions, the tetracycline production can be enhanced more than eight times (12.3 mg g-1 biomass for immobilized cells vs. 1.5 mg g-1 biomass for free cells) in comparison with free-cell mycelial cultures.
Assuntos
Antibacterianos/biossíntese , Carragenina/química , Clortetraciclina/biossíntese , Excipientes/química , Streptomyces aureofaciens/metabolismo , Tetraciclina/biossíntese , Antibacterianos/química , Técnicas Bacteriológicas , Células Imobilizadas/química , Clortetraciclina/química , Géis , Concentração de Íons de Hidrogênio , Microesferas , Modelos Biológicos , Concentração Osmolar , Cloreto de Potássio/química , Streptomyces aureofaciens/citologia , Tetraciclina/química , Fatores de TempoRESUMO
We have previously developed [(1987) Biochemistry 26, 5200-5208] the use of trans-diamminedichloroplatinum(II) to induce reversible RNA-protein crosslinks in the ribosomal 30 S subunit. Protein S18 and, to a lesser extent, proteins S13/S14, S11, S4 and S3 could be crosslinked to the 16 S rRNA. The aim of the present work was to identify the crosslinking sites of protein S18. Three sites could be detected: a major one located in region 825-858, and two others located in regions 434-500 and 233-297. This result is discussed in the light of current knowledge of the topographical localization of S18 in the 30 S subunit and of its relation with function.