Dynamic modeling of methylotrophic Pichia pastoris culture with exhaust gas analysis: From cellular metabolism to process simulation

A systematic approach to establish a dynamic model of methylotrophic Pichia pastoris culture in bioreactor is presented on the basis of biomass compartmentalization and metabolic stoichiometry simplification. Besides direct state variables (i.e., biomass, glycerol, methanol, and ammonia), CER and OUR calculated from on-line exhaust gas analysis are included in the model. The model is directly and crossly validated with five experimental cultures involving glycerol growth and methanol feeding phases. Model parameters are identified with confidence intervals. Meanwhile, data consistency is straightforward checked between predicted CERs and measured CTRs. In addition, in the light of the model structure, the results of parameter sensitivity analysis verifies the relative “freedom” of biomass initial compartmentalization and the high output sensitivity when the substrate (glycerol or methanol) concentration is close to the affinity constant (KGly or KMeth). With the proposed model, a process control strategy can be accordingly developed, which is based on real-time monitoring and regulating of cellular metabolic state during culture.

highlights
► A stoichiometric model of central metabolism with data consistency check.
► The biomass “activity” (compartmentalization) accounting for cellular dynamics.
► The relative “freedom” to choose the initial biomass activity.
► Valuable for real-time monitoring and control of the cellular metabolic state.