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• Bioprocesses use living microorganisms such as bacteria and fungi, to produce valuable bioproducts which are industrially or medically important
• Bioproducts produced by bioprocesses

  • Antibiotics
  • Vitamins
  • Hormones
  • Enzymes
  • Organic acids
• Most bioprocesses are employed inside a bioreactor
• Bioreactor


  Vessels or tanks in which whole cells or cell-free enzymes transform raw materials into biochemical products and/or less undesirable by-products
• Biological systems involved in bioreactors

  • Enzymes
  • Microorganisms
  • Animal cells
  • Plant cells
  • Tissues
• The microbial cell itself is a miniature bioreactor
• Shake flasks, Petri dishes, and industrial fermenters too are bioreactors
• Bioreactor


  The heart of a bioprocess since conversion occurs here
• Basic function of a bioreactor

  • Provide optimum conditions for cell physiology and metabolism by regulating various chemical and/or physical factors
• Criteria for classifying bioreactors

  • Type and form of biocatalyst: free cells in submerged cultures; carried bound or immobilized cells/enzymes
  • Mode of operation: batch; continuous; fed-batch
• Main criteria for designing a bioreactor

  • Adequate oxygen transfer
  • Low Shear Stress
  • Adequate mixing
• Bioreactors are commonly cylindrical in shape ranging in size from liters to cubic meters
• Bioreactors are often made up of stainless steel material
• Low shear stress (LSS) in bioreactor


  Minimal force or stress exerted on the components within the reactor due to fluid flow
• Importance of low shear stress in bioreactor

  • Cell Viability - High shear stress can damage delicate biological components (e.g., enzymes)
  • Product Yield - LSS helps structural integrity of the product, higher yields and better quality
  • Steady-State Conditions: LSS helps maintain steady-state conditions in continuous culture
  • Mixing and Mass Transfer - LSS conditions can promote efficient mixing of nutrients, gases, and MOOs within the reactor, facilitates mass transfer
• Basic features of a bioreactor

  • An agitator system
  • An oxygen delivery system
  • A foam control system
  • A temperature control system
  • A pH control system
  • Sampling ports
  • A cleaning and sterilization system
• Agitator


  Provides good mixing so that the temperature of medium is uniform inside the bioreactor
• Important parts of a bioreactor

  • Baffle - used to break the vortex formation in the vessel
  • Sparger - supplies adequate oxygen to cells
  • Jacket - provides the annular area for circulation of constant temperature water
  • Impeller - performs the important tasks of mixing, aeration, heat and mass transfer
• Components of a bioreactor


  • Top-plate
  • Inoculation pipe
  • Drive motor
  • Impeller shaft
  • Impeller
  • Stirrer
• Bioreactor is also called fermenter (with slight differences) in fermentation industry

  
• Similarities between Bioreactor & Fermenter

  • Both are closed systems
  • They are affected by aeration, temperature, pH, nutrition, and sterility
  • The vessels used are made of stainless steel and are cylindrical in shape
  • They are used in industries for large-scale production
• Differences between Bioreactor & Fermenter


  • Fermenter is a type of bioreactor that is specialised only to carry out fermentation
  • Bioreactor is closed vessel that facilitates different types of biochemical reactions
  • Fermenter only produces acids and alcohols, Bioreactor produces metabolites such as pharmaceuticals, drugs etc
  • Fermenter only uses fermentative microbes, Bioreactor uses unicellular microbes, plant and animal cells
• Properties of a Fermenter/Bioreactor

  • It should be reliable for long-term operation
  • It should be capable of being operated aseptically or should provide sterile conditions
  • It provides adequate aeration and agitation for uniform mixing
  • It should consume less power
  • It should be equipped with controlling probes for temperature, pH, oxygen level etc
  • It should facilitate the passage of inoculum and media
  • It should not allow excessive evaporation loss
  • It should minimize the labour input for operation, harvesting, cleaning and maintenance
• Types of Fermenter/Bioreactor


  • Stirred tank fermenter
  • Airlift fermenter
  • Fluidized bed fermenter
  • Packed bed fermenter
  • Photo fermenter

  
• Principal bioreactor configurations


  • Bubble column
  • Airlift
  • Stirred tank
  • Packed bed
• Stirred Tank Fermenter


  Mechanical stirrers (using impellers) are used to mix the reactor to distribute heat and materials (such as oxygen and substrates) - Oxygenation and agitation
• Sparger in Stirred Tank Fermenter

  To introduce air or other gases
• Purpose of Stirred Tank Fermenter

  • To provide a controlled environment for the growth and cultivation of microorganisms (MOOs) to produce specific products through fermentation processes
• Stirred tank reactors use mechanical agitation as the mixing method
• Airlift bioreactors (ALB)/biofermenters


  • Pneumatic (operated by air pressure)
  • Use gas (usually air) to circulate the fermentation broth, providing O2 to the MOOs and promoting mixing without the need for mechanical stirring
• Airlift fermenters can be used in the cultivation of photosynthetic bacteria and algae
• Advantages of Airlift Bioreactors (ALB)

  • Elimination of attrition (abrasion) effects generally encountered in mechanical agitated reactors
  • Can be used for both free and immobilized cells
• Fluidized Bed Fermenter (FBF)


  It operates on the principle of fluidization, where a solid particulate material (usually support particles) is suspended and mixed with a gas or liquid to create a fluid-like environment
• Fluidized Bed Fermenter (FBF)


  • Used in biotechnology and fermentation processes
  • The top portion is more expanded to reduce the velocity of the fluid
  • The bottom part is slightly narrow to retain the solid particles inside the vessel
• Advantages of Fluidized Bed Fermenter

  • Mixes the contents uniformly
  • Maintains the uniform temperature gradient
  • Can be used for continuous operation
  • Produces higher volumetric productivity
  • Little or no clogging of particles
• Packed Bed Fermenter (PBF)


  • Used in the cultivation of microorganisms (MOOs), in biotechnology and fermentation
  • Designed with a solid support matrix, typically in the form of solid particles or a porous column, in which MOOs are immobilized and allowed to grow
• Packed Bed Fermenter


  • The solid matrix possesses properties like porous or non-porous, highly compressible, and rigid
  • A nutrient broth continuously flows over the immobilized biocatalyst, and the product is released into the fluid at the bottom
• Advantages of Packed Bed Fermenter

  • Low operation cost
  • Provides continuous operation
  • Separation of the biocatalyst is easy
• Disadvantages of Packed Bed Fermenter

  • Undesired heat gradients
  • Poor temperature control
• Fermentation can be divided into two main processes/stages as upstream processing and downstream processing