This work proposes a passivity based formulation and control of a well-mixed reactor model for a set of chemical and biochemical reactions. Gibbs free energy is an apt Hamiltonian function for isothermal cases. An energy based model of such systems is proposed which is quasi Port-Hamiltonian, based on physical grounds. The model is taking care of the concentration space and reaction space of a chemical reaction. Stoichiometric and Reaction interconnection and damping assignment passivity based controllers (IDA-PBC) are derived from these models. Control of enzymatic hydrolysis of cellulose in...