No abstract

A microbiological screening program was instituted to search for an animal rennet substitute. Among 381 bacteria and 540 fungi tested, only one organism, Endothia parasitica, yielded a suitable enzyme substitute. The fungal rennin enzyme was crystallized and some of its properties were studied. It was found to be watersoluble, nondialyzable, precipitable with (NH4)2SO4 and organic solvents (e.g., acetone and isopropanol), and destroyed by heating for 5 min at 60 C. It was determined to be most stable in water at pH 4.5 and to have an isoelectric point of pH 5.5. On acid hydrolysis, it yielded: alanine, ammonia, arginine, aspartic acid, cysteic acid, cystine, glutamic acid, glycine, histidine, isoleucine, leucine, phenylalanine, proline, serine, threonine, tyrosine, and valine. No tryptophan was detected after alkaline hydrolysis. Its molecular weight was estimated to be in the range of 34,000 to 39,000. The milk-clotting activities of the fungal and animal rennins proved to be essentially identical in milk containing various concentrations of CaCl2. Both rennins manifested comparable clotting activities in milk at pH 6.0 to 7.0.

No abstract

A total of 58 cultures, tentatively identified as species of the genus Cephalosporium, were screened in flask fermentations for their ability to effect conversions of progesterone (A4-pregnene-3,20-dione) and Reichstein's Substance S (A4-pregnene-17a,21-diol-3,20-dione). A large number of transformations were observed by means of a series of five paper chromatography systems rated for analysis of steroid compounds ranging in polarity from progesterone to polyhydroxylated steroids. Five different transformation products were selected for isolation and identification. For purposes of recovery, conversions were conducted under submerged conditions in either 4or 200-liter fermentors in which the broth was agitated and aerated. The steroid substrate was dissolved in acetone and added aseptically to the growing culture in a final concentration of 0.025 %. After the conversions were effected, the whole broth was extracted with chloroform, and the transformation products were recovered, either by direct crystallization from solvents or through the use of silica gel columns. It was determined that C. ciferrii 21C converted progesterone to A4-androstene-3 ,17-dione. Kendall's Compound F (A4-pregnene-1113,17a,21-triol-3,20-dione) was converted to its 20,B-ol analogue by Geotrichum sp. 51C (during these studies, a number of cultures were taxonomically reclassified). Cephalosporium sp. 27C formed the Al-analogue of Reichstein's Substance S, and Cephalosporium sclerotigenum 31C and Verticillium aphidum both converted Substance S to the 6#-hydroxy derivative. Paecilomyces persicinus 22C converted Substance S to a product believed to be a dihydroxylated derivative.

A microbiological screening program was instituted to search for an animal rennet substitute. Among 381 bacteria and 540 fungi tested, only one organism, Endothia parasitica , yielded a suitable enzyme substitute. The fungal rennin enzyme was crystallized and some of its properties were studied. It was found to be water-soluble, nondialyzable, precipitable with (NH 4 ) 2 SO 4 and organic solvents (e.g., acetone and isopropanol), and destroyed by heating for 5 min at 60 C. It was determined to be most stable in water at p H 4.5 and to have an isoelectric point of p H 5.5. On acid hydrolysis, it yielded: alanine, ammonia, arginine, aspartic acid, cysteic acid, cystine, glutamic acid, glycine, histidine, isoleucine, leucine, phenylalanine, proline, serine, threonine, tyrosine, and valine. No tryptophan was detected after alkaline hydrolysis. Its molecular weight was estimated to be in the range of 34,000 to 39,000. The milk-clotting activities of the fungal and animal rennins proved to be essentially identical in milk containing various concentrations of CaCl 2 . Both rennins manifested comparable clotting activities in milk at p H 6.0 to 7.0.