There are a total of 1858 metabolites (94.31%) without a formula: __iECx55__pcresol_c, __iECx55__5drib_c, __iECx55__aacald_c, __iECx55__amob_c, __iECx55__mththf_c, ...

To be able to ensure that reactions are mass-balanced, all model metabolites ought to be provided with a chemical formula. Since it may be difficult to obtain formulas for certain metabolites this test serves as a mere report. Models can still be stoichiometrically consistent even when chemical formulas are not defined for each metabolite. Implementation: Check if each cobra.Metabolite has a non-empty "formula" attribute. This attribute is set by the parser if there is an fbc:chemicalFormula attribute for the corresponding species in the SBML.

This model contains 1278 unconserved metabolites: __iECx55__acnam_c, __iECx55__2dh3dgal6p_c, __iECx55__ascb__L_e, __iECx55__alaala_e, __iECx55__acgam1p_p, ...

The list of unconserved metabolites is computed using the algorithm described in section 3.2 of "Detection of Stoichiometric Inconsistencies in Biomolecular Models." Bioinformatics 24, no. 19 (2008): 2245. doi: 10.1093/bioinformatics/btn425.