350 BACTERIOLOGICAL CHEMISTRY 



or ill raffiiiose, 



CH2OH 



(galactose) 



but not in melezitose, 



(glucose) 



CH3OH 

 (fructofuranose) 



CiljOH 

 (glucose) 



nor in normal fructose, 



(fructos.) 



(glucose) 



CH2OH— C.OH— HOCH— HCOH— HCOH— CH2 



I I 



which has a fructopyranose structure, is necessary for 

 the formation of levan. The conversion of sucrose smd 

 raffinose into levan can also be accomplished by an 

 enzyme, levansucrase, which is secreted into the medium 

 by B. mesenteric us and B. suhtilis ; B. polymyxa and 

 Aerohacter levanicwn form an endocellular levansucrase 

 which has the same effect. Levansucrase has no action on 

 Neuberg's ester, Harden and Young's ester, methyl- y- 

 fructoside or inulin, all of which contain a terminal 

 fructofuranose group. Along with levan a reducing 



