E.coli has a higher pH range and may be easier to assemble, but may be less productive.
Yeast will probably be more productive in the long run but is otherwise inferior
Genes
we need an open reading frame (orf) a ribosome binding site (rbs), promoter, and terminator
at least 3-5 enzymes: pepsin, salivary amylase, trypsin, chymotripsin, pancreatic amylase