The Michaelis-Menten kinetics are specified in the uptakekinetics subroutine.

      subroutine updatekinetics(nlp, nextmet, nec, t, y, v)
c     Michaelis-Menten uptake kinetics for batch simulation 
c     of anaerobic growth of E. coli (iJR904) on glucose 
c     and xylose.
      implicit none
      integer nlp, nextmet, nec, ny
      double precision t, y(*), v(*)
      double precision vgmax,vOmax,vZmax,KO,Kg,Kie,KZ,Kig

      ny = 1 + nlp + nextmet
c     Constants
      vgmax = 10.5d0
      Kg    = 0.0027d0
      Kie   = 20.0d0
      vZmax = 6.0d0
      KZ    = 0.0165d0
      Kig   = 0.005d0
      vOmax = 15.0d0
      KO    = 0.024d0
c     Uptakes kinetics for glucose, xylose and oxygen
      v(1) = -vgmax*y(3)/(Kg+y(3))*1/(1+y(5)/Kie)
      v(2) = -vZmax*y(4)/(KZ+y(4))*
     &               1/(1+y(3)/Kig)*
     &               1/(1+y(5)/Kie)
      v(4) = -vOmax*y(6)/(KO+y(6)) 
      end