Batch and Fed-batch Fermentation

Modes of Fermenter Operation 1Batch and Fed-batch fermentation

Pramono, H.

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• Sue Macauley-Patrick and Beverley Finn, Practical Fermentation Technology

Introduction

• The purpose of this presentation is to describe (briefly) various modes of operation avaiable for fermentation

• Large quantity of products, production, nature of secondary metabolites production different modes of fermentation

• Based on modes:– Batch fermentation– Fed-batch fermentation– Batch continuous fermentation

Graphicaly

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Batch culture

• Batch fermentation is the simplest mode of operation, and often used in laboratory to obtain substantial quantities of cells or products for further analysis

• Close system, in one batch containing:– Nutrient– Starter microbes

• In end fermentation process the batch containing:– Nutrient (depleted)– Starter microbes– Product(s)

Termination of fermentation process

• The fermentation is terminated when one or more of the following has been reached:

1. Microbial growth has stopped due to the depletion of the nutrients or the build of toxic compounds

2. After fixed predetermined period of time3. The concentration of desired product has been

achieved

Batch culture growth curve

• When cells are grown in a batch culture, they will typically proceed through a number of distinct phase– Lag phase (may or may not be present) must be

minimize, how?– Log phase – Stationary – Initial of death

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Growth of associated product (primary metabolites)

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Growth associated product

• Example of commercial growth associated products– Ethanol produced bay Saccharomyces cerevisiae– Amino acid (MSG) produced by Corynebacterium

glutamacium– Riboflavin produced by Ashbya gossipii– Citic acid produced by Aspergillus niger– Xanthan gum produced by Xanthonomonas campestris– Vitamin B12 produced by Pseudomonas denitrificans

Secondary metabolites

• Most antibiotics are produced as secondary metabolites

• Fermentation can then stopped just before the cells enter the death phase

Advantages of batch culture

1. Simplicity of use2. Operability and reliability3. Production of secondary metabolites that are not

growth-related4. Fewer possibilities of contamination5. Easy to assign a unique batch number to each run

Disadvantages of batch culture

1. Culture ageing, differentiation bad production2. Build up toxic metabolites can be restrict cell growth and

product formation3. Initial substrates concentrations may have to be limited due to

problems with inhibition and repression (like: carbon repression)

4. Batch to batch variability5. Non productive periods to maintain the facilities6. Degeneration of production7. Heterogeneous and constantly changing culture

Fed-batch culture

• Fed-batch culture is essentially similar to batch culture

• Most of fed-batches begin live with a straighforward batch phase

• Different: do not operate as closed systems• The different feeding regiment, different growth/

process inside the batch

Various curve vs Batch culture

Variable feeding regime

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Continuous feeding regime

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Intermittent feeding regime

Incremental feeding regime

Advantages and disadvantages of various feeding strategies

Feeding strategy Advantages DisadvantagesVariable •Minimizing by-product

formation•Substrate converted to biomass, product or both

•Controlled by feedback control•Requires accurate monitoring and operator control

Continuous •Allow bioprocess to run without operator control

•Must have historical process trend data

Intermittent •Allows feed to be fully utilised before further addition•Reducing catabolite repression

•Controlled by feedback control•Requires accurate monitoring and operator control

Incremental •Allows feed to increase with biomass formation•Optimizing growth rate and product formation

•Controlled by feedback control•Requires accurate monitoring and operator control

Advantages of Fed-batch Culture

1. Controlling the concentration of the limiting substrate prevent repressive effects of high substrate concentration

2. Avoids catabolite repression3. High cell density (up to ten times compared to batch

culture)4. Increased production of non-growth-related

secondary metabolites5. Reduction of broth viscosity

Disdvantages of Fed-batch Culture

1. Detailed knowledge of the organism’s growth and product formation pattern is required

2. Deficiency of reliable online sensors for accurate substrate determination in near real time

3. Without feedback control, fed is predetermined and therefore does not allow for any fluctuation within the bioprocess

4. The process operator must be fully trained and highly skilled

Batch and Fed-batch features

1. Small quantities of products can be obtain from laboratory production

2. Products may not able to be stored for long periods

3. High product concentration optimation4. Instability of some production5. Fewer technical difficulties

Any questions?