Fermentor
Fermentation
• Group of chemical reactions induced by microorganisms or enzymes that split complex organic compounds into relatively simple substance
Anaerobic conversion of sugar to carbon dioxide and alcohol by yeast
Fermentor
• Available – varying sizes – total volume capacity
• Small laboratory fermentors – 1 – 15 lts
• Pilot plant fermentors – 25-100-2000 gallons
• Range – 5000 – 10,000 gallons
• Actual operating volume – less than that of total volume
• Head space – top – above the liquid medium – splashing, foaming and aeration
• Head space – a fifth to a quater
Fermentor Design
• Fermentor – strong enough to withstand the pressure of large volumes of aqueous medium
• Fermentor vessel – capable of operating aseptically – number of days
• Adequate aeration and agitation – provided – meet the metabolic requirements of m/o – mixing should not damage the organism
• Power consumption should be as low as possible
• A system of temperature control should be provided
• A system of PH control should be provided
• Sampling facilities – provided
• Evaporation losses = not excessive
• Additional inoculum or seed tanks – small sized Fermentor – inoculum is produced – added directly to the fermentor
• Drain or mechanism – bottom of fermentor – remove the completed fermentation broth
• Vessel should be designed – require minimal use of labour in operation, harvesting, cleaning and maintenance
• Smooth internal surfaces
• Material of vessel – withstand repeated steam sterilization cycles
• Small scale – Glass or stainless steel
• Glass –smooth surfaces, non-toxic, corrosion proof and easy to monitor
Impeller
• Impeller(stirrer)
• Agitation –
• Air dispersion
• Oxygen transfer
• Heat transfer
• Maintain uniform environment throughout the vessel
• Enhancement of mass transfer between dispersed phases
Baffles
• Four baffles to eight – incorporated – vessel – prevent vortex – improve aeration efficiency
• Metal strips roughly one tenth of vessel diameter – attached radially to the wall
• Baffle should be installed – gap between the vessel wall and baffle – scouring action – minimizes the microbial growth on the baffles and fermentor walls
Sparger – Aeration System
• Device – introducing air – liquid – Fermentor
Three types
- Porous sparger
- Orifice sparger
- Nozzle sparger
• Pipe – minute holes
• Hole size – 1/64 – 1/32 inch or larger
• Allows air under pressure to escape as tiny air bubbles into the liquid medium. Small size hole – requires great air pressure
Sterilization of Air Supply for Fermentation
• Sterile air – large volumes – aerobic fermentation process
• Heating and filtration – main methods of sterilization
• Heating is generally too cost for full scale operation
• Glass wool, glass fiber – filter material
Cooling Coil
• Temperature – important factor
• High temperature – ferments – destroyed
• Very low temperature – reaction – slow
• Optimum temperature – maintained
• Growth temp of M/o —– may or may not coincide with optimum temp of fermentation
• To maintain optimum temp – fermentor should be cooled
• Passing cold water –inside wall of tank or jacketed walls of tank
Sterile Filter
• Sterilization of air – entering fermentor – sterile filter
• Composed cotton wool – trap m/o in air
• Form the filter – air – carried through sterile piping – bottom of the fermentor – beneath the impeller blade
Antifoam
• Aeration and agitation – liquid medium – foam – if media containing protein or peptides
• Not controlled –raise to headspace – tank – along with spent air
• Condition may cause – contamination and limits the gas exchange between the medium and the atmosphere of the head space
• Antifoaming agents – Lowers the surface tension and decreases the stability of the foam bubbles – burst
• Two types
• Inert antifoam agents – Silicone compounds
• Too expensive – adv – Not utilized by m/o and non-toxic
• Antifoams – crude organic materials – animal or vegetable oils – Lard oil, corn oil and soyabean oil or long chain alcohols like octadecanol
• Not inert, toxic, provide additional nutrients to the m/o
• Fatty acid of the antifoam – lower the PH of the medium
• Added – manually or automatic
• Automatic – sensing mechanism used – foam risen into headspace of fermentor – product touches the electrode – current produced – activate pump to add antifoam agent
Sterilization of Medium
• Pure culture fermentation – medium to be sterilized
• Small scale – medium placed directly – fermentor – autoclaved
• Large tanks – not feasible
• Medium+ water – — pumped into retention tubes and heat exchangers before passing into fermentation tank
• Retention tube contain – steam jet heaters – inject high pressure steam in to the medium – to sterilize it as it passes through the pipes
• Rate of passage – adjusted – provide complete media sterilization without overcooking
Summary
• Anaerobic conversion of sugar to carbon dioxide and alcohol by yeast
• Fermentor vessel
• Baffles
• Impeller
• Cooling coil
• Antifoam agent
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