To model the performance of a continuous cross-flow separation unit (CCSU) for the isolation of nopinone from methanol-water solvent, a series of hypothetical dead-end batch separation units (DBSU) were considered (illustrated in Figure of the main text). In this model, each hypothetical DBSU obeys the experimentally determined performance metrics for this system, which describe the observed solute rejection and transmembrane flux at a given feed solute concentration (presented in Figure of the main text). Additionally, each DBSU is operated at a fixed incremental concentration factor, 𝐶𝐹 O.A ,which must not exceed the concentration factor maintained during experimental measurements.