Design of Fermenter

Lecture

Basic functions of a fermenter for microbial or animal cell culture

• The vessel – capable of being operated aseptically for a number of days

• Adequate aeration and agitation – meet requirements of micro-organisms

• Power consumption should be as low as possible

• Temperature control and pH should be provided

Basic functions of a fermenter for microbial or animal cell culture

• Sampling facilities should be provided

• Evaporation losses from fermenter should not be excessive

• Minimal use of labor in operation, harvesting, cleaning and maintenance

• Should have internal smooth surfaces

• Similar geometry of both smaller and larger vessels

Aseptic operation and containment

• Aseptic operation involves protection against contamination

• Containment involves prevention of escape of viable cells from a fermenter or downstream equipment

• Lowest level hazard micro-organisms – require GILSP

Achievement and maintenance of aseptic conditions

• Sterilization of fermenter• Sterilization of air supply and exhaust gas• Aeration and agitation• Addition of inoculum, nutrients and other

supplements• Sampling• Foam control• Monitoring and control of various parameters

Construction materials - Body

• Possible to use glass and/or stainless steel

• Glass vessel with a round or flat bottom and a top flanged carrying plate – autoclave

• Largest possible diameter-60cm

Construction materials - Body

• A glass cylinder with stainless-steel top and bottom plates

• More expensive (50%)• Pilot-scale and industrial scale – stainless steel

Construction materials - Body

• Aseptic seal – made between glass and glass, glass and metal or metal and metal joints between fermenter vessel and a detachable top or base plate

• Compressible gasket, a lip seal or an ‘O’ring

Temperature control

• Provision of heat – fermenter in thermostatically controlled bath or by use of internal heating coils or by a silicone heating jacket through which water is circulated

• Silicone jacket consists of silicone rubber mats wrapped around the vessel

• Cooling surface/cooling water

Aeration and Agitation

• Aeration – provide microorganisms in submerged culture with sufficient oxygen for metabolic requirements

• Agitation – uniform suspension of microbial cells in homogeneous nutrient medium

• Mechanical agitation is required in fungal and actinomycete fermentations

Structural components involved in aeration and agitation

• Agitator (impeller)

• Stirrer glands and bearings

• Baffles

• Aeration system (sparger)

Agitator (impeller)

• Achieve mixing objectives – bulk fluid and gas-phase mixing, air dispersion, oxygen transfer, heat transfer, suspension of solid particles and maintaining uniform environment throughout vessel contents

Baffles

• Four baffles incorporated into agitated vessels of all sizes to prevent vortex and to improve aeration efficiency

• Metal strips roughly one-tenth of vessel diameter and attached radially to the wall

• Minimizes microbial growth on baffles and fermenter walls.

Aeration system (sparger)

• Introduces air into liquid of fermenter

• Three basic types – porous sparger

- Orifice sparger – a perforated pipe

- Nozzle sparger – an open or partially closed pipe

- Combined sparger-agitator

Sterilization of the fermenter

• Designed – for steam sterilization under pressure

• Medium may be sterilized in vessel or separately and added aseptically

Sterilization of air supply

• Sterile air – large volumes in many aerobic fermentation processes

• Heat (expensive) and filtration

Sterilization of exhaust gas from a fermenter

• Sterilization of exhaust gas can be achieved by 0.2 μm filters on outlet pipe

• Aerosol formation may occur in fermenter and moisture and solid matter may then plug filter

• Filters – checked to ensure that no viable cells are escaping

Feed ports

• Addiiton of inoculum, nutrients and other supplements

• Sampling ports to test• Additions of acid/alkali – silicone tubes

pumped by peristaltic pumps after aseptic connection

• In larger fermenter nutrient reservoirs and associated piping- integral parts – can be sterilized with vessel

Foam control

• Minimize foaming

• Excessive foaming – danger that filters become wet resulting in contamination

• Siphoning – loss of all or part of contents of fermenter

• This project is funded by a grant awarded under the President’s Community Based Job Training Grant as implemented by the U.S. Department of Labor’s Employment and Training Administration (CB-15-162-06-60). NCC is an equal opportunity employer and does not discriminate on the following basis:

• against any individual in the United States, on the basis of race, color, religion, sex, national origin, age disability, political affiliation or belief; and

• against any beneficiary of programs financially assisted under Title I of the Workforce Investment Act of 1998 (WIA), on the basis of the beneficiary’s citizenship/status as a lawfully admitted immigrant authorized to work in the United States, or his or her participation in any WIA Title I-financially assisted program or activity.

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