|MadSci Network: Microbiology|
I have been unable to find any examples of microbes producing cyanide and to the best of my knowledge I do not believe it is energetically or physiologically advantageous for a microbe to produce cyanide or hydrogen cyanide (industrially, production is very energy consuming). Therefore I don't think there is any CN production in the human body resulting from the activities of micro-organisms.
Alcohol (presumably ethanol) and methane are produced as waste by-products by certain bacteria during growth. Bacteria known as methanogens use carbon dioxide as their terminal electron acceptor (a terminal electron acceptor is necessary for cellular energy production) converting it into methane This reaction is known as methanogenesis. Alcohol is also produced as the result of a cellular energy reaction (in yeast). This reduction of pyruvate leads to the formation of ethanol. Propane is not likely to result as a final by-product in cellular respiration, (i.e. its formation will not occur during reduction of a electron acceptor). Propane may be a by-product from microbial degradation of more complex hydrocarbons however, harvesting of propane through this method would not be energy nor economically efficient.
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