MICROBES — man's MIGHTY MIDGETS 41 



gillus oryzae, as that used for amylase manufacture by the mold-bran proc- 

 ess. However, other strains must be employed since high amylase producers 

 are seldom optimal for protease production, and vice versa. Products of such 

 origin find their greatest application in the preparation of chill-proofing 

 agents used in the manufacture of beer and ale. Proteases of bacterial origin 

 are of much greater importance, industrially. These are produced also by 

 selected strains of Bacillus subtilis and the processes of manufacture dupli- 

 cate, in the main, those employed for the production of bacterial amylase, 

 except that different substrates and operating conditions favoring maximum 

 protease production are employed. Bacterial proteases find important in- 

 dustrial applications in the degumming of silk, the baiting of hides, the 

 digestion of fish livers to release oil, and in the recovery of silver from 

 photographic plates. Their largest use is for the preparation of spot removers 

 (in combination with other enzymes) for the dry-cleaning industry, an out- 

 let which exceeds $1 million annually. 



There is an increasing market for the pectin-hydrolyzing enzymes in the 

 food industries. Whereas many microorganisms produce such enzymes, species 

 of Penicillium (e.g., P. jrequentans) are generally employed for their manu- 

 facture. This can be accomplished either by a shallow-tray or deep-tank 

 operation. Best yields are obtained in the presence of pectin-rich substrates 

 such as fruit wastes and beet cossets, a by-product of the beet-sugar industry. 

 A variety of pectic enzymes are produced, and to some degree the commer- 

 cial products are fashioned to meet specific applications. They are used pri- 

 marily for the clarification of fruit juices, wines, jellies, and syrups and to 

 prevent fruit-juice concentrates from jelling. 



Invertase, an intracellular enzyme, is obtained commercially from the yeast 

 Saccharomyces cerevisiae, although it is produced in substantial amounts by 

 certain molds and bacteria. The yeast is grown in the presence of sucrose un- 

 der conditions which favor heavy cell growth. The yeast cells are then recov- 

 ered, and allowed to undergo autolysis under toluene, after which the cell 

 debris is removed and the enzyme is precipitated with ethyl alcohol. The 

 product is commonly marketed as a 60 per cent concentrate dissolved in 

 glycerol. It finds its chief use in the manufacture of invert sugar, and pos- 

 sibly its most striking application is in the production of soft- or liquid- 

 center candies, e.g., chocolate-covered cherries. 



Some additional enzymes of microbial origin are produced commercially 

 that have important, if more limited, applications, including: catalase, pro- 

 duced in submerged cultures of Aspergillus niger, is used in the manufacture 

 of surgical gut, in the bleaching of furs, and for the perpetuation of plati- 

 num blondes; glucose oxidase, similarly produced by A. niger, finds appli- 

 cations in the desugaring of eggs, and in the processing of foods where 

 residual glucose must be oxidized to preclude enzymatic browning; penicil- 

 linase, produced in deep tanks by Bacillus cereus or B. subtilis, is used to in- 



