Growing Mould

I am attempting to culture Apergillus sojæ, the fungus responsible for making soya sauce. This is the results of my first attempt:

Photo of Aspergillus

I did this by making a malt extract plate, then pouring a small amount of soy sauce on it and swirling it around. I have concern that this is not quite the right stuff. A. sojæ and A. oryzæ, the fungus responsible for making miso, are closely related to the dangerous A. flavus and A. parasiticus which produce alfatoxin, a carcinogenic toxin. Fun! Morphological distinction of the between them is not easy and the domesticated strains still contain most of the genes to make alfatoxin, though they do not seem to function. There are plating methods, strangely involving coconut, that can determine if alfatoxin is being produced, and I intend to follow up with those.

For a moment, I was going to name this, as I normally name fungal contaminants, but I realised that this was not a contaminant. I will first have to subculture and then try an alfatoxin test. How I do a positive control remains to be seen.

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