The study of the poultry needs in basic nutrients allowed the development of a scheme for obtaining feed polypeptides (“polypeptide cassettes”) enriched with L-amino acids, which are necessary for the metabolism of birds. The amino acid and nucleotide profiles of about 500 bioinformation sequences of thermostable plant proteins and archaea were studied, on the basis of which candidate sequences were selected. In silico, the amino acid and domain composition of the thermostable polypeptides has been optimized. A library of genetically engineered constructs encoding optimized polypeptides with the necessary composition of L-amino acids irreplaceable for poultry has been created. Primary E. coli producer strains were obtained, and the expression and thermostability of the target polypeptides were studied.