Structured modeling and state estimation in a fermentation process: Lipase production by Candida rugosa

Area of Science:

• Biotechnology and Biochemical Engineering
• Microbial Fermentation
• Mathematical Modeling

Background:

• Lipase production by Candida rugosa is influenced by extracellular oleic acid, which is transported into the cell for consumption and storage.
• Lipase is excreted into the medium and distributed between aqueous and oil-water interphases.
• Cell growth is regulated by intracellular substrate concentration.

Purpose of the Study:

• To develop a structured mathematical model for lipase production in Candida rugosa.
• To implement a state and parameter estimation methodology for real-time monitoring and control.
• To validate the model and estimation strategy against experimental data.

Main Methods:

• A mathematical model was developed based on biological hypotheses of lipase production and cell growth.
• A recursive prediction error algorithm estimated biomass (X) and specific growth rate (mu) using CO2 evolution rates.
• An adaptive observer estimated intracellular substrate and a kinetic parameter (A), with extracellular substrate calculated via material balance.

Main Results:

• The model successfully described lipase production, incorporating substrate transport, lipase excretion, and growth modulation.
• The estimation strategy effectively determined biomass, intracellular and extracellular substrate, and kinetic parameters.
• The developed estimator demonstrated good performance in simulation and experimental tests.

Conclusions:

• The developed mathematical model and estimation methodology are suitable for process control and monitoring of lipase production.
• The approach integrates on-line exhaust gas analysis for efficient state and parameter estimation.
• This work provides a robust framework for optimizing fermentation processes.