POLYSACCHARIDR8 OF MICRO-ORGANISMS 351 



sugar is formed, glucose from sucrose, and melibiose (not 

 galactose) from raffinose, showing that the latter is not 

 first hydrolysed to sucrose. No carbohydrate is des- 

 troyed in the conversion, showing that the process is 

 independent of respiration. Many strains of Str. saUvarius 

 synthesise levan from sucrose aii^ raffinose. B. lactis 

 produces a fructosan from sucrose only. In the sugar- 

 refining industry contamination with Leuconostoc and 

 B. mesentericiis causes considerable loss as the result 

 of the " viscous fermentations " to which they give rise. 

 B. lactis pituitosi gives rise to the formation of a galactan 

 which is excreted into the medium. 



Mycodextran, [a]D-|-251°, a polyglucose giving no 

 coloration with iodine, is produced by the mould P. 

 expansum. A number of other glucose polysaccharides 

 of varying degrees of molecular complexity have l)een 

 described giving colours with iodine ranging from no 

 colour through red to blue and purple. Mycogalactan, 

 [a]D-f284°, yielding galactose on hydrolysis, is formed 

 by the growth of A. niger on a glucose medium. This 

 production of a polysaccharide built up of sugar units 

 different from those of the sugar on which the organism 

 grew is not an isolated case ; a number of such conversions 

 are now known. The formation of cellulose from a variety 

 of carbon sources by Acetohacter xylinum has already been 

 described. P. liiteum produces an acid polysaccharide, 

 luteic acid, when grown on glucose. Luteic acid is 

 hydrolysed by dilute mineral acid to yield one molecule 

 of malonic acid and two molecules of glucose. The 

 malonic acid is linked through one carboxyl group to a 

 neutral polysaccharide, luteose, from which it can be 

 removed by treatment with dilute alkali. Besides luteic 

 acid, however, the mould also produces other polysac- 

 charides built up of fructose, galactose or mannose, even 

 when it is grown on glucose as the sole source of carbon. 

 The converse of this phenomenon also occurs ; when 

 P. liitemn is grown on galactose, mannose, fructose, 



