MICROBES man's MIGHTY MIDGETS 39 



conditions could produce this vitamin in yields that warranted the conduct 

 of fermentations in which it was the primary product. Today, vitamin B12 

 is regularly recovered in crystalline form and marketed for pharmaceutical 

 use. Much greater quantities are sold as vitamin-rich concentrates, which, as 

 in the case of riboflavin, are used for the supplementation of poultry and ani- 

 mal feeds. In the latter case the product is sold upon the basis of its vitamin 

 content, and it may represent a product recovered from the residues of one 

 of the Streptomyces antibiotic fermentations, or it may have its origin in 

 special fermentations designed to yield maximum vitamin concentrations. 

 Vitamin B12 is an exceedingly active compound biologically, and it is com- 

 monly used at levels of only 1.5 to 2.0 fig. per pound of feed. This being true, 

 it is fabulously expensive on a weight basis, the U.S. P. crystalline compound 

 being priced at about $250 per gram. The wholesale value of vitamin B12 

 currently produced in the United States is estimated at $20 to $25 million per 

 year. 



Vitamin D is regularly produced by the irradiation of ergosterol, which is 

 generally obtained from yeast, but which can be recovered from the mycelia 

 of a variety of other fungi, including that used for the penicillin fermentation. 



MICROBIAL ENZYMES 



Enzymes of microbial origin have been used for centuries in the Orient 

 for the conversion of starch and the degradation of certain plant proteins, 

 but it is only within the past half century that significant information con- 

 cerning their nature or activities has become known. Prior to that time, 

 selected "kojis," consisting of some type of farinaceous materials seeded 

 with appropriate microorganisms, were used to effect the breakdown of starch 

 preparatory to alcoholic fermentation or the partial decomposition of pro- 

 teins (e.g., those of soybeans) for the manufacture of soy sauce and other 

 fermented foods and condiments. The kojis were perpetuated empirically 

 by the implantation to new substrates of fragments from previously grown 

 kojis of proven activity and their incubation under environmental conditions 

 which favored the desired microorganisms. Thus by trial and error, regimens 

 for such enrichment cultures were evolved which ensured their effectiveness 

 with reasonable reproducibility. Kojis wherein different types of micro- 

 organisms predominated were used for different purposes; e.g., in the manu- 

 facture of soy sauce two separate kojis were employed: a mold koji that 

 effected both a conversion of the starch in rice and parched wheat and 

 brought about a partial breakdown of the bean proteins, and a second koji 

 in which yeasts and lactobacilli predominated that was used for the sec- 

 ondary brine fermentation. 



The first serious attempts to utilize the responsible enzymes per se were 

 made by a Japanese investigator, Takamine, around the turn of the century. 



