de - Beste verfügbare Techniken (BVT) - Umweltbundesamt

Fermentation stage
Chapter 2
The fermentation stage is carried out in a large stirred fermenter (from some m 3 to 200 m 3 or
more) and is an aerated, batch-fed process. The batched medium is designed to support only a
limited amount of further growth and is steam-sterilised within the fermenter. After sterilisation,
it is inoculated with the final seed stage broth. Further sterilised nutrients are added
continuously (“fed”) during the fermentation in such a way that the growth of the microorganism
is precisely controlled and the conditions made favourable for antibiotic production.
The process lasts up to eight days.
Stock cultures
filtered air
growth medium
H 2 O
Auxiliaries
Solvent
Salt, alkali, acid
H 2O
Auxiliaries
Filtration or
centrifugation
Precipitation
Filtration
Product
Extraction
Purification and
concentration
Seed stage
Fermentation
Ion-exchanger
Spray drying
Product
Exhaust gas
Biomass or
broth, auxiliaries
Biomass
or broth, VOC
Biomass
and broth
Solvent, VOC
Solvent or broth,
auxiliaries, VOC
Figure 2.32: Typical sequences of operations for fermentations and downstream work-up
Possible input materials (on the left) and the associated waste streams (grey background)
Product work-up
The following work-up steps depend on the properties and location of the product. The products
are obtained by separation of the biomass from the broth by:
• filtration (conventional or ultrafiltration) and extraction of the filtered broth with an organic
solvent and pH adjustment (e.g. penicillin G) or extraction of the biomass with organic
solvents (e.g. steroids)
• filtration (conventional or ultrafiltration) and product precipitation from the filtered broth by
adjusting the pH and/or by the addition of auxiliaries (e.g. tetracyclines)
• pH adjustment and processing of the unfiltered broth over an ion-exchanger (alkaloids,
amino acids)
• direct spray drying of the unfiltered broth (e.g. for feed industry purposes).
Intracellular products need an additional mechanical step of cell destruction before extraction.
OFC_BREF Dezember 2005 69