Rhizopus arrhizus
Rachel E. Johns
Rhizopus arrhizus, a filamentous fungus, has been shown for quite some time to be an incredibly useful microorganism, both in research and in biotechnology.  One of its most extraordinary uses is as a steroid transformer, converting diosgenin obtained from Mexican yams into an intermediate that can easily be used to cheaply produce cortisone.  Prior to this biological method of production, thirty-seven chemical steps were used to produce cortisone from deoxycholic acid extracted from bile.  Some of these steps required high temperatures and pressures, as well as expensive solvents.  These extreme steps, along with the extremely low 0.15% conversion of deoxycholic acid into cortisone, led to a cost of $200 per gram.  Later, Durey H. Peterson and others at the Upjohn Company discovered that Rhizopus arrhizus could be used to greatly reduce production costs.  The starting material (diosgenin) for this biological method has up to a 95% conversion into cortisone.  The intermediate produced by Rhizopus arrhizus requires only six additional chemical steps.  These factors resulted in a rapid drop in price to $6 per gram, falling to $0.46 per gram by 1980.  This success is a great achievement for biotechnology, and a good example of how a simple microorganism, Rhizopus arrhizus, can be used to benefit society. Another beneficial use of this microorganism is lipase production by companies including Fluka Pharmaceuticals and Kampoyaki Neutriceuticals.  This enzyme is generally sold to universities and other institutions for research purposes. Rhizopus arrhizus has also been used as a research tool to study biosorption of hard and soft metal ions. Both the types and amounts of metals that can be absorbed and the mechanism of absorption can be studied using this organism.  This has been an important area in environmental engineering, and is a very promising method of cleaning up metal pollution.

Rhizopus arrhizus does have some detrimental effects, however. It has been known to cause pole rot in tobacco plants, head rots in sunflowers, and Rhizopus root rot in beets.  In humans, it has caused cutaneous zugomycosis in a surgical wound as well as mucormycosis.  These cases are generally seen in patients already weakened due to other
problems.  This microorganism is most remarkable in the improvements and potential benefits that it has given and continues to give to society. It is an excellent example of how many other microorganisms, both well-known and currently undiscovered, may also be used to improve our lives.

Dixon, Bernard.  Power Unseen.  New York:  W.H. Freeman, 1996.

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*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.


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