Fermentation

Comprehensive modelling power and flexibility

Modelling microbial fermentation poses substantial challenges in many aspects.

gPROMS provides the necessary framework for comprehensive modelling of fermentation processes to a level of detail – and hence accuracy – that has not been possible before.

All process analysis functions from the initial process feasibility to final design, control and optimisation of the process operation can be completed without leaving the gPROMS environment.

PSE has also developed state-of-the-art open models of fermentation processes, which can be supplied as part of a ModelCare agreement.

Our approach is to work closely with customers to customise our generic models for specific processes based upon individual needs.

Structure of a typical model

The following are typically required in order to establish a reliable and valid model of the fermentation reactions for each process and product of interest.

1. Stoichiometric description of reactions

Describing the reactions directing the production of the micro-organisms, metabolic intermediates, secondary metabolites, and end products is critical to effective modelling of the fermentative process. The fundamental elements of the model include

a. Characterisation of the micro-organism with regard to

type (facultative, obligate, strict, unicellular, mould)
elemental composition – i.e. C_aH_bO_cN_d
yield factors - substrate specific
inorganic constituents - phosphorus, sulphur, potassium, etc.

b. Elemental material balance for growth

aerobic growth without product formation
detailed representation for aerobic growth of chemoheterotrophic organisms (ATP generation or utilisation)
anaerobic glucose fermentation

c. Product formation

Class 1 - main product results from primary energy metabolism (e.g., ethanol from anaerobic growth of yeast)
Class 2 - main product arises indirectly from energy metabolism (e.g., citric acid formation during aerobic mold cultivation)
Class 3 - product is a secondary metabolite (e.g., penicillin)
Class 4 - Biotransformation

2. Reaction Kinetics

Balanced growth kinetics
Transient growth kinetics and unstructured batch models
Structured models – compartmental or metabolic
Product formation kinetics – unstructured or structured models

3. Biological Reactors

Ideal bioreactors
Fed-Batch reactors
CSTR cell reactors with recycle and wall growth
Ideal plug-flow tubular reactor

4. Bioseparations

Removal of particulates – methods for filtration, centrifuging and settling
Primary isolation – solvent extraction, sorption, precipitation and ultrafiltration
Purification – chromatography, adsorption
Final product isolation – crystallisation, drying, organic solvent removal