190 GENERAL MICROBIOLOGY 



8. What is the value of such microbial action in soil? 

 Where are starch-digesting microorganisms present in 

 nature? Of what importance? 



9. State results in full and draw any conclusions. 

 Point out any practical applications of the above. 



REFERENCES 



BAYLISS: Nature of Enzymic Action, pp. 25, 113. 

 MARSHALL, C. E.: Microbiology (1911), pp. 90, 106, 248, 463, etc. 

 EULER, HANS: General Chemistry of the Enzymes, pp. 13-15, et al. 

 HAWK, PHILIP B.: Physiological Chemistry (1914), pp. 10, 48, 50, 



61, 65. 



SADTLER, S. P.: Industrial Organic Chemistry, p. 186. 

 LAFAR: Technical Mycology, Vol. II, Part 2, pp. 351-353. 



EXERCISE 15. TO SHOW THE ACTION OF REDUCING 

 ENZYMES 



Apparatus. Petri dish; medium fine sand; sulphur; 

 cake of Fleischmann's compressed yeast, fresh (obtain 

 this yourself); small mortar and pestle; lead acetate 

 paper. 



Method. 1. Thoroughly grind the sulphur, sand and 

 yeast cake in a small mortar. 



2. Place the contents of the mortar in a covered dish 

 with a piece of moistened lead acetate paper. What odors 

 are noted? 



3. What reaction is demonstrated by the lead acetate 

 paper? What reactions are taking place? Give a chemical 

 equation which will cover the final changes. May other 

 enzymes be released from the yeast cells during the process 

 of maceration? If so, what enzymes? 



What names are applied to the specific enzyme acting on 

 sulphur and to the class to which it belongs? Where does 

 this action occur in nature? 



This enzymic action was first observed in 1888 by a Frenchman, 

 J. de Reypailhade, who found that the alcoholic extract of yeast would 

 convert elementary sulphur into sulphuretted hydrogen. 



