Investigation of a polysaccharide produced from sucrose by Betabacterium vermiformé (Ward-Meyer)

Abstract

WE have been able to examine a polysaccharide formed from sucrose by an organism (Betabacterium vermiformg) recently studied by Prof. A. J. Kluyver, to whom we are greatly indebted for a culture. The organism was isolated by Mr H. D. Meyer (private communication) in the course of an extensive and careful bacteriological examination of "Tibi-complex ". The latter originates in Mexico where it occurs in the form of hard granules on the disk-shaped leaves of the Opundia plant. It has long been used by the natives for the preparation of a beverage by fermentation and is analogous to the classic example, the Kephir yeast of the Arabs. As in the case of Kephir, Tibi fermentation is due to the symbiotic action of a yeast and a bacterium. The bacterium isolated by Meyer appeared to be identical with that isolated by Ward [1892] from the Ginger-beer plant. On a sucrose-gelatin medium, the bacterium readily formed colonies surrounded by a highly viscous secretion and its growth on gelatin slopes closely resembled that of Betacoccw8 arabinosaceous anhaemolyticus (Leuconostoc mesenterioides). Meyer was able to show that the viscous secretion consisted mainly of a polyglucose with properties strikingly similar to those of the dextran synthesized by B. arab. anhaemolyticus [Tarr & Hibbert, 1931]. We have been able to confirm the finding that it is indeed a dextran, resembling closely in physical properties the dextrans from both B. arab. haemolyticus and B. arab. anhaemolyticu8. Our preliminary investigations were concerned with production of the polysaccharide in a liquid medium. The medium adopted for preparing the dextran from B. arab. haemolyticus [Stacey & Youd, 1938] was unsuitable for the growth of Betabact. vermiforme although when a satisfactory substrate for the latter was devised certain similarities in the growth of the two organisms were observed. Both dextrans could be synthesized from sucrose only; moreover, in each case it was mainly the glucose constituent of the sucrose molecule which appeared to be utilized in the growth. For consistent dextran production both organisms required a source of available nitrogen which was best supplied by maple syrup to B. arab. haemolytics and by yeast extract to Betabact. vermiforme'. The poly-saccharide could conveniently be prepared in yields amounting to 20% of the sucrose employed in a simple yeast extract-sucrose medium. The growth reached a maximum in about 10 days and was quite uniform even in large volumes of liquid-a property which facilitated the large-scale dextran production. Separation of the polysaccharide was effected by alcoholic precipitation followed by washing and drying by the usual methods. The crude material contained approx. 0.2% N and was insoluble in water. This insolubility differentiates it from the Leuconostoc dextrans which are readily soluble in water. (1946)