Energy minimization study is applied to an amino acids downstream process for L-methionine production currently in

operation and energy-saving options that can be implemented in practice are systematically identifi ed with the application

of Process Integration (PI) design method. Structural changes in process fl owsheets or reconfi guration in stream-mixing

patterns are considered for the debottlenecking of bioprocesses for energy reduction, which allows the energy-effi cient use

of steam for the purifi cation of bioproducts and its effl uent management, leading to maximum 18% saving in steam use to

be achieved. Reduction in cold utility is investigated with the strategic use of cooling water reuse, as a means of cold utility

minimization, with which up to 33% of cooling water use can be reduced. The introduction of multi-level expansion for the

provision of refrigeration utility is further identifi ed, leading to 35% reduction in compression power. The retrofi t case study

clearly demonstrates the usefulness of Process Integration method for energy minimization in bioprocesses in operation and

its results provides practical design guidelines for energy-saving projects in amino acids production.