430 PRINCIPLES OF SOIL MICROBIOLOGY 



Chemically, the true celluloses are non-nitrogenous, amorphous 

 polysaccharides, exhibiting a characteristic fibrous structure. They 

 are insoluble in simple solvents and soluble in ammoniacal copper 

 solution, in ZnCl 2 and strong acids (H 2 S0 4 ), giving a dark brown to 

 violet color with chlor-zinc iodide. They are very resistant to the 

 action of plants, animals and majority of microorganisms, but they can 

 be hydrolized by strong acids and certain specific microorganisms. 

 They occur only in a natural state (plant tissues) and have not as yet 

 been synthesized in the laboratory. Cotton contains 87 to 91 per 

 cent celulose; wood of evergreens, 60 per cent; and cereal straw, 35 

 per cent. The empirical formula for cellulose is that of polysacchar- 

 ides, namely (C 6 Hi O 5 )n, the same as that of starch. It contains 44.42 

 per cent carbon and 6.22 per cent hydrogen. The ratio of oxygen to 

 hydrogen is 8:1. On hydrolysis of cellulose, substances with an alde- 

 hyde (d-glucose united by cellobiose linkages) grouping are obtained. 



Various formulae have been suggested to account for the chemical 

 structure of the cellulose molecule. This is looked upon either as a 

 polymerized molecule of cellobiose held together by strictly primary 

 valencies or as a colloid molecule held together by secondary or residual 

 valencies. 



When hydrolyzed by means of acetic acid anhydride and sulfuric 

 acid, the cellulose swells and goes into solution in the form of a colloidal 

 cellulose slime. On further hydrolysis, the disaccharide cellobiose is 

 obtained (only about 36 per cent): 



r -° — — i 



CH 2 OH • CHOH • CH • CHOH • CHOH • CHO 

 CHOH • CHOH • CHOH • CH • CH • CH 2 OH 



L o 1 



This consists of two molecules of d-glucose and differentiates cellulose 

 from starch, which on hydrolysis gives first maltose, then glucose. 11 



2(C 6 H 10 6 )„ + nH 2 = nC 12 H 22 On 



C 12 H 22 O u + H 2 = 2C 6 Hi 2 6 

 cellobiose glucose 



The existence of a reducing trisaccharide (procellose) as a possible 

 intermediary product of hydrolysis between cellulose and cellobiose 



11 Skraup, Z. H., and Konig, J. tlber Cellose, eine Biose aus Cellulose. Ber. 

 deut. cbem. Gesell., 34: 1115-1118. 1901. 



