I'm not sure the reports say its contamination. Its possible the powder is just incompatible with the digestive system of some people in same way as, say, leafy vegetables or carrageenan affect some people's digestion but not others.

Soylent may be recalling because they don't want to be liable in the _possibility_ of contamination. However, over time, they may find they can make the best product that is compatible with some digestive systems but not others - put a warning on product accordingly.

Cheap, accurate testing of foods for compatibility with a broad range of nutrient absorption rates and microbiomes would be key in engineering foods for everyone. But right now it would just make your food really expensive to the extent its even possible.