Microbial dehydrogenation

A third advancement in microbial biotechnology of steroid production was the abiUty to introduce a 16a-hydroxyl group microbiologicaHy (163). Modifications of the liP-hydroxylation, 16a-hydroxylation 1,2-dehydrogenation microbial processes are used for the synthesis of hydrocortisone, prednisolone, triamcinolone, and other steroid pharmaceuticals. A few microbial transformations that have been used to manufacture steroids are Hsted in Table 1 (164). 

Sobering investigators uncovered a second significant breakthrough in microbial biotechnology of steroid production. They discovered that Corynebacterium simplex converted hydrocortisone (cortisol) (29) to prednisolone via a 1,2-dehydrogenation reaction. This A -3-ketosteroid is a highly active antiinflammatory commercial product (162). 

The use of microbial 1-dehydrogenations is essential to the manufacture of corticosteroids, as chemical dehydrogenation processes are commercially non-competitive. 

In every case the information provided has been obtained by collating public domain sources of information, but unfortunately very often little data is available, particularly on commercial aspects, even for products that have proved to be big successes. Thus microbial biotransformations for steroid modification, particularly stereoselective hydroxylations, such as the use of Rhizopus arrhizus to convert progesterone into antiinflammatory and other dmgs via 11- -hydroxyprogestrone, have proved to be very successful. However, comparatively little useful information exists from public domain sources, despite (or perhaps because) a market of hundreds of millions /a exists for such microbially transformed steroids (cortisone, aldosterone, prednisolone and prednisone etc.) produced by microbial hydroxylation and dehydrogenation reactions coupled with complimentary chemical steps. 

Similar microbial oxidations of terminal methyl groups accompanied by degradation and dehydrogenations of the carbon chains take place in alkyl benzenes [1053, 1071]. 

Microbial 4,5-di-dehydrogenation of 5a-androstane-3,17-dione involves abstraction of 4/8-H." ... 

The NADH is derived from glyceraldehyde 3-phosphate dehydrogenation. Thus, yeast fermentation yields ethanol rather than lactate as an end product of glycolysis. Small amounts of ethanol are produced by the microbial flora of the gastrointestinal tract. Other types of fermentation using similar reactions occur in microorganisms and yield a variety of products (e.g., acetate, acetone, butanol, butyrate, isopropanol, hydrogen gas). 

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