1995 2007 Biotechnology A Textbook of Industrial Microbiology

1995 2007

• Biotechnology: A Textbook of Industrial Microbiology Wulf Crueger , Anneliese Crueger translated by A. Mortazavi 2 nd edition (25 Oct 1991) • Fermentation microbiology and biotechnology Mansi El-Mansi, Charles F. A. Bryce translated by M. Rabani, 2007

Fermentation technology • Fermentation tecchnology is the oldest biotechnological process • Beverage industry, vinegar, baking yeast, citric acid, lactic acid, antibiotics, …. • Microbiologists consider fermentation as:

• energy-generating processes where organic compounds act as both electron donor and acceptor (Metabolism) • the growth of large quantities of cells under aerobic or anaerobic conditions, within a fermenter or bioreactor (Industrial Microbiology)

Fermentation process • upstream processing (USP): Preservation , improvement, inoculums, media prep. fermenter sterilization, control and production • downstream processing (DSP): separation, extraction and purification

Fermenter design and construction • The main function of a fermenter is to provide a suitable environment • Most are designed to maintain high biomass concentrations • The performance of any fermenter depends on agitation rate, oxygen transfer, p. H, temperature and foam.

• Laboratory fermenters • Industrial fermenters ØThese are mostly purpose-built and designed for a specific process Øorganism, the optimal operating conditions required for target product formation, product value and the scale of production

• Large volume, low value products are usually produced using relatively simple fermenters • extreme p. H or high temperatures • some food fermentations and waste-water treatment • fermentations producing high value, relatively low volume products

• most fermentations are now performed in closed vessels designed to exclude microbial contamination • Small fermenter are constructed from glass or stainless steel • If aseptic operation is required, all associated pipelines need to be sterilizable, usually by steam.

• cleaning-in-place (CIP) • Associated pipework must also be designed to reduce the risk of microbial contamination. • Pressure gauges and safety pressure valves

Control of chemical and physical conditions • Agitation of suspended cell fermentations is performed in order to mix the three phases within a fermenter. • Agitation prolongs retention of air bubbles in suspension • maintenance of suitable shear conditions during the fermentation is very important

Stirred tank reactors • agitators or impellers within a baffled cylindrical Vessel

• STRs are the most commonly used vessels and have been adopted for a wide range of fermentation processes. • The effectiveness of agitation • STRs must create high turbulence

airlift fermenter

deep-jet fermenter

• The mixing of nutrients and gaseous exchange within any fermenter is complex • Laminar and turbulent flow • Reynolds number (Re)

• When fluids are stirred they may behave as follows: • Newtonian fluids • Non-Newtonian fluids • Viscoelastic fluids

Heat transfer • In fermenter design, efficient heat transfer is important in controlling the temperature • Heat transfer is primarily achieved using an outer jacket surrounding the internal phase or via internal coils.

Aeration • Some fermentations operate anaerobically, but the majority are aerobic • Sterile filtered air or oxygen normally enters the fermenter through a sparger system • During aerobic fermentations molecular oxygen must be maintained at optimal concentrations