Biomedical subjects
Publications and source records attributed to N N Grechushkina.
The source of carbon and nitrogen as well as pH of medium influence the possibility of synthesis of the exocellular heteropolysaccharide of Mycobacterium cyaneum and the quantitative harvest of glucan but not its monomer composition. The conditions of mycobacterial growth and glucan synthesis usually do not coincide.
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A medium has been selected for providing the maximum synthesis (7-8 g/litre) of a free exocellular polysaccharide by Mycobacterium lacticolum 121. The following concentrations of the components are optimal for the biosynthesis: hexadecane, 5.0-6.5% (by volume); NaNO3, 2.0-4.0 g/litre; Na2HPO4-12H2O, 1.0-1.5 g/litre; KCl, 1.0-1.5 g/litre. An increase in the concentration of sodium nitrate and phosphate over 4.0 and 1.5 g/litre, respectively, favours growth of the cells but inhibits biosynthesis of the polysaccharide. Concentrations of hexadecane and potassium chloride over 6.5% and 1.5 g/litre, respectively, have no effect of the culture and yield of the polysaccharide.
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Mycobacterium lacticolum 121 grows and synthesizes exopolysaccharide at the initial values of pH of the medium from 5.0 to 11.5. The accumulation of biomass is maximal (10 to 12 gram/litre) at pH 6.0 to 11.5; the rate of growth is highest at pH 8.0 to 11.5. The largest amount of exopolysaccharide (2.0 to 2.4 gram/litre) is produced in the medium at pH 8.0 to 11.0; the rate of its production is highest at pH 9.0 to 11.0. The growth of Mycobacterium lacticolum 121 and the biosynthesis of polysaccharide are optimal at pH 8.0 to 8.2. Changes in acidity of the medium have no effect on the qualitative composition, structure, and molecular weight of the polysaccharide.
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Mycobacterium salivarium 76 was found to synthesize the individual exoglycan unbound to proteins and lipids in media containing various sources of carbon (sugars, polyatomic alcohols, n-alkanes) and nitrogen (nitrates and ammonium salts) at pH from 6 to 10. These compounds determined the quantitative yield of glycan, but had no effect on its monomeric composition represented by glucose, mannose, uronic acid and pyruvate residues. The highest yield of biomass and polysaccharide was found in the medium with n-dodecane and KNO3 at pH 7.0.
Exocellular polysaccharides were synthesized by ten strains of 7 saprotrophic mycobacterial species in parallel with their growth. The cultures grew and produced polysaccharides more rapidly in a medium with glucose than in a medium with n-hexadecane. The polymers are homogeneous acid heteroglycans of the regular structure. All of them contain glucose and some of them contain hexuronic acid. Galactose, fucose, mannose, ramnose and pyruvic acid are found in some of the polysaccharides. The exoglycans of two mycobacterial species contain mannolactylic acid. Beta-glycosidic linkages prevail in most of the polysaccharides.
Mycobacterium mucosum 32 synthesizes an extracellular heteropolysaccharide during its growth in media with different sources of carbon (sugar, polyatomic alcohols, n-alkenes) and nitrogen (nitrates, ammonium salts) within the pH range from 6 to 10. The yield of the polysaccharide depends on the cultural growth and on several factors of the medium. The monosaccharide composition of the glycan does not change depending on the conditions. It contains glucose, galactose, mannose and uronic acid. This exopolysaccharide is an individual compound which is not bound to proteins or lipids.