Clinical-size dextran by direct fermentation (with NRRL B-1351 Streptococcus sp.)

• Published in: Journal of biochemical and microbiological technology and engineering 1960-12, Vol.2 (4), p.381-399
• Main Authors: Rogovin, S. P., Senti, F. R., Benedict, R. G., Tsuchiya, H. M., Watson, P. R., Tobin, R., Sohns, V. E., Slodki, M. E.
• Format: Article
• Language: English
• ISSN: 0368-1467; 1547-173X
• DOI: 10.1002/jbmte.390020402

Dextran, a polymer of glucose, has been widely used as a blood‐plasma volume expander. In whole culture fermentations most dextran‐producing organisms elaborate dextrans that have molecular weights of many millions and must be depolymerized and fractionated to obtain a product suitable for clinical use. An exception however is Streptococcus sp. (Strain DS–50) NRRL B–1351. In the work described here, this organism is used to produce clinical‐size dextran in high yields, both on a laboratory‐ and a pilot‐plant scale. With this process, fractionation is required but depolymerization is not. Fermentations of media containing 15 per cent sucrose are complete in less than 48 hours with 0·2 per cent inoculum. Yields of native dextran and clinical‐size dextran by methanol precipitation are 68 and 43 per cent of the theory, respectively. The structurally heterogeneous dextran formed by NRRL B–1351 has a higher viscosity for a given molecular weight than does NRRL B–512 dextran. The viscosity–molecular weight relationship for the former may be expressed by the equation [η] = 6·51 × 10−4Mw0·554. The high‐molecular weight fraction had approximately 75 per cent of 1,6‐like linkages, as compared with 87 per cent for the clinical fraction. All fractions had a lower ratio of 1,6 to non‐1,6 linkages than did NRRL B–512 dextrans.