156 GENERAL BIOCHEMISTRY 



casein ol milk. Commercial rennet is prepared from the fourth or 

 true stomach of the calf. Preservatives such as boric acid, benzoic acid, 

 or large amounts of sodium chloride are sometimes added to prevent 

 decomposition of the enzyme preparations by bacteria. Most of the 

 millions of pounds of cheese produced annually in the United States 

 is made with the aid of rennet. 



The processing of fruit juices has grown from a very small industry 

 20 years ago to a relatively large one. This growth has been due in 

 part to the ability of producers to clarify juices with the aid of 

 enzymes. A mixture of pectic enzymes is added to the juice to hy- 

 drolyze the pectic substances causing turbidity. 



All woven fabrics contain starch or other sizing applied to the 

 warp threads to strengthen the yarn before weaving. If these fabrics 

 are later bleached, printed, or dyed, this sizing must be removed, 

 commonly by hydrolysis with amylases. The enzyme methods of de- 

 sizing are more satisfactory than those employing acid or alkali because 

 these latter agents attack cellulose and weaken the fabric. Several 

 enzyme products for desizing cloth are manufactured in the United 

 States from bacteria, fungi, malt, or other biological materials. 



In the manufacture of leather, proteolytic enzymes prepared from 

 such materials as the pancreas or Bacillus mesentericus are used to 

 hydrolyze the proteins of the hair follicles, thus freeing the hair so 

 that it may be readily scraped from the hides. Enzymes can be used 

 in dry cleaning for the removal of stains due to glue, gelatin, or starch. 

 Amylases are employed to prepare a partially hydrolyzed starch as 

 surface coating for paper. Pepsin is used to digest gelatin in the 

 process of recovering silver from photographic film. 



Processes that employ microorganisms for the production of specific 

 chemical substances are, in effect, applications of enzymology. Such 

 processes produce lactic, acetic, citric, gluconic, and gallic acids, 

 L-sorbose, acetone, butanol, ethyl alcohol, and many other products. 



Digestive disturbances due to an insufficiency of enzymes have been 

 treated for many years by supplying the lacking enzymes. Pepsin, 

 papain, bromelin, and amylases aid digestion in the mouth and 

 stomach. Pancreatic enzymes can be supplied by encapsulating them 

 in material that is not dissolved in the stomach but is soluble in the 

 juices of the duodenum. The enzymes are not released, therefore, 

 until they arrive at the site of action. 



Sloughing wounds and abnormal conditions such as bed sores, 

 furuncles, ringworm, and other suppurative skin diseases have been 

 alleviated by means of proteolytic enzymes from the pig pancreas. 



