If you have the right yeast.
QUOTE
One possibility would be to keep the drug-producing strains of yeast under lock and key, much like how the DNA sequences of smallpox are kept safe from the public. Still, Dueber said, "An additional concern is that once the knowledge of how to create an opiate-producing strain is out there, anyone trained in basic molecular biology could theoretically build it."
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Diogenes of Sinope:
"It is not that I am mad, it is only that my head is different from yours."
"Other dogs bite only their enemies, whereas I bite also my friends in order to save them."
Arnold Judas Rimmer, BSC, SSC:
"Better dead than smeg."