Metabolites – primary and secondary

Learning Outcomes• Compare and contrast the processes of continuous culture and batch

culture.• Describe the differences between primary and secondary

metabolites.

Metabolism and metabolites• Metabolism (process)• Sum total of all the chemical reactions• Processes produce

• New cell and cell components• Chemicals• Waste products

• Metabolites (products)• A substance produced during cell processes

Primary and secondary metabolites• Primary metabolite• Substance produced by organism as part of it’s normal growth• E.g. amino acids, proteins, enzymes• Production of primary metabolites matches the growth in population

• Secondary metabolite• A substance only produced

at a particular growth phase• No direct involvement in

fundamental metabolite processes• Production usually begins

after the main growth phase of the micro organisms

Primary Metabolites• Primary metabolites are produced during active cell growth [lag, exponential,

stationary], matches the growth in population of the organisms• Produced by all microorganisms

Secondary Metabolites• Secondary metabolites are produced near the onset of stationary

phase e.g antibiotic chemicals• Not produced by all microorganisms

Batch culture• Starter population is mixed with a specific quantity of nutrient

solution• Allowed to grow for a fixed period• Products removed• Fermentation tank emptied• Examples

• Penicillin production• Enzyme production

Continuous Culture• Nutrients are added and products are removed from the fermentation

tank at regular intervals• Examples

• Insulin production from genetically modified E.Coli• Production of mycoprotein

A batch fermenter

Why use Batch?• Many secondary products are not growth associated• Genetic instability• Operability and reliability• Economic considerations

Exam Practice – Unit 5 questions• 99, 125, 141, 170

Q141 Unit 5 questions

Primary metabolites

Secondary metabolites

A fermenter