Microbial transformation or
biotransformation is the ability of m.o. to modify a wide variety of organic
compounds to produce useful products.
It is a
very helpful tool for:
1-Production
of more useful & sensitive products
2-Elucidation
of chemical structure of complex compounds
Biotransformation
reactions include various types of hydroxylation, oxidation, epoxidation,
reduction, epoxidecleavage, hydrolytic or condensation reactions
Biotransformation
applies for steroids, antibiotics, hydrocarbons & terpines.
The
transformation reaction is considered to be a detoxification
.reaction by the
m.o. using induced enzyme
Different biotransformation processes
using growing cultures, resting cells, spores, immobilized cells, enzymes orimmobilized enzymes are currently applied. When growing cells areused,them.o. is cultured in a suitable medium until a suitable microbial growth is
reached
The substrate is then added in a &biotransformation is monitored until maximum product is reached
Advantages of using spores or resting
cells over culturing
Reduction of cost-
Lowering the contamination risk-
Reduction of byproducts-
Steroid
biotransformation
Steroids are group of lipid compounds
having the same basic cyclopentano-phenanthrenenucleus.
Steroids such as
estrogen, progesterone and androgens are used as therapeutics
Progesterone
and estrogens derivatives are used as contraceptives and cortisone derivatives
as anti-inflammatory agents in rheumatoid arthritis.
One of the
major biotechnological aspects in this area is the application of a wide range
of the microorganisms including bacteria and fungi in converting steroid
substances into the pharmacologically active compounds or other useful intermediates.
Steroid
biotransformation
Low cost
sterols of animal origin such as cholesterol & of plant origin such as
diosgeninare converted chemically to progesterone which in turn is used as a
substrate for biotransformation.
Actinomycetesincluding
Rhodococcus, Mycobacterium, Corynebacterium,Arthrobacterand Nocardiaspecies,
have become widely recognized as bacteria able to rapidly degrade sterols,
producing steroid pathway intermediates that find application as precursors in
drug synthesis.
Neurosporacrassa,
Aspergillusand Rhizopusnigricansare example of fungi used in
biotransformation of steroids.
Steroids
can be produced by chemical synthesis, but the process is laborious &
expensive. As example, chemical conversion of deoxycholicacid (bile acid) to
cortisone required 37 steps & yielded 1 g cortisone from 615 g
deoxycholicacid. The price of 1 g cortisone was reduced from 200$ to only one $
or less when the process was conducted by Rhizopusnigricans.