World Resources 
difficult to know what you would get if you tried to select for 
lysine or any other essential amino acids. 
Pirie: Some strains of maize are quite rich in methionine— 
they are up to 3-5 per cent, so a mixture containing some maize 
could probably be made to give an adequate balance of essen- 
tial amino acids. 
Crick: What about microbiological treatments? Do they 
convert a substantial amount of protein into microbiological 
protein, which is possibly higher in essential amino acids? 
Pirie: They are no higher; but why convert protein into 
protein? Most of the yeasts and micro-organisms will grow on 
carbohydrates and inorganic nitrogen. 
Crick: I suggested it because I thought you found that the 
microbiological “‘protein”’ tasted better! 
Lederberg: If you are talking about a requirement of some- 
thing like 1 gram of an essential amino acid per day, as a rough 
order of magnitude, then looking ahead something like 10 to 
20 years, do you think it unlikely that chemical synthesis will 
be able to furnish such materials at a cost commensurate with 
the need ? 
Pirie: Synthesis should certainly be an economic proposi- 
tion, but why bother? Biological systems do it quite efficiently. 
I see no reason why a factory should be preferable in the long 
run. In principle, a mixture of maize, as a calorie source, with 
leaf-protein as a protein source, ought to be about right. 
Nobody has tried to see whether theory and practice agree. We 
have been making leaf-protein starting from materials such as 
pea waste normally discarded in the process of quick freezing 
green peas. Because I agree with Colin Clark’s strictures on 
porridge, we have also gone into the question of presentation of 
our leaf-protein on the table. I regard eating as something 
different from stoking; so we go right through from processing 
the crop to presenting the product at table. 
Hoagland: What percentage yield do you get per ton of leaf? 
Pirie: We get about 50 to 70 per cent of what is present in 
a good leaf. The percentage recovery falls as the initial protein 
content of the leaf falls. We have made several types of press 
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