48 RAPER 



containing 7 p.p.m. of this drug before entering distribution channels. The 

 further use of antibiotics for food preservation undoubtedly offers an in- 

 creasingly important outlet for the future. 



MICROBIAL CONVERSIONS 



One of the newest and most exciting industrial applications of microor- 

 ganisms is in the area, still poorly defined, that is oftentimes referred to as 

 microbial conversions. This has stemmed naturally from a growing appre- 

 ciation of the biosynthetic potentialities of microorganisms, and from the 

 equally important fact that almost any microbial cell can be propagated in 

 tank culture if sufficient attention is given to its nutrition, oxygen require- 

 ments, incubation temperature, pH, etc. Probing investigations are in progress 

 on many frontiers, and there can be little doubt that some of these explora- 

 tions will in time open new horizons wherein microorganisms can contribute 

 handsomely to man's further progress. Already there is one very striking and 

 singularly successful example. This relates not to the production of a specific 

 end product as in most fermentations, but rather to the utilization of micro- 

 organisms to effect a series of intricate, costly, and time-consuming chemical 

 steps in the S5aithesis of cortisone. In this development, Durey H. Peterson 

 and his associates at the Upjohn Laboratories have played a leading role. 

 Starting with meager clues that microorganisms could possibly effect a series 

 of necessary modifications in the molecule of progesterone, many microorgan- 

 isms were surveyed. The bread mold, Rhizopus arrhizus, was found to do the 

 job, and to do it in a manner that permitted a commercially feasible fermen- 

 tation process. Three pharmaceutical firms now use microorganisms to effect 

 steroid transformations. The market value of cortical hormones in 1955 

 amounted to $75 million, of which production three-quarters was based upon 

 microbial conversions. 



As one would expect, this is currently an area of intense research activity 

 and in it cortisone occupies the position that penicillin did in the antibiotic 

 field in the mid-forties. No one can predict where the next "breakthrough" 

 will come, but microbiologists are confident that the future for microbial 

 conversions is indeed bright. The microorganisms with which they work 

 are subtle and profound, and they are withal amazingly diverse in the bio- 

 synthetic capabilities they have already demonstrated. 



If I have seemed to emphasize the economic aspects of microorganisms in 

 their service to man, let us not conclude that these, important as they are, 

 represent the truest measure of their contributions. Of infinitely greater im- 

 portance has been their roles in providing the agents for the alleviation of dis- 

 ease and the improvement of human and animal nutrition. To appreciate these 

 facts one need only contemplate the rare incidence of many diseases such as 

 pneumonia, scarlet fever, and many others, the lessening ravages of tuber- 



