1. TYPES OF BIOREACTOR
Dr Bhavesh Patel
Principal
V P & R P T P Science College, Vallabh Vidyanagar
2. Back ground
A Bioreactor is one in which biological reactions takes
place.
Bioreactor is also known as fermentor
Fermentation is an important reaction carried out by
biological system, importantly by microorganisms.
Fermentation can be defined as an oxidation reduction
energy yielding process where both oxidizing and reducing
agents are organic compound.
The process of fermentation was first observed by Louis
Pasteur who gave the concept of “Germ theory of
fermentation”. According to him the fermentation is
mediated by germs i.e. microorganism. (the process was
originally considered as a chemical process)
3. Back ground
Previously the process of fermentation was considered as
an anaerobic process where a sugar or starch containing
substrate is converted in to alcohol with the help of yeast.
Present definition of industrial fermentation is
“Bioconversion of any substrate in to its product”
Hence, any process that is mediated by biological system is
known as fermentation.
Presently we are producing many products at industrial
scale like alcohol, amino acids, vitamins, antibiotics, organic
acids etc. (students must try to prepare a comprehensive
list of products produce along with producer organisms)
4. Types of Fermentation
Fermentation is of two types namely, Surface and
submerged
As the name indicate in surface fermentation the organisms
tends to grow on surfaces. This type of process is mainly
applicable to fungi and involve the use of solid or semisolid
substrate. The present day process which involves the
concept of surface fermentation is solid state fermentation.
The other type of fermentation involves the cultivation of
organisms beneath the surface (submerged). Such process
mainly involves cultivation of bacteria using liquid media.
Submerged cultivation can be carried out by two ways i.e.
Batch cultivation and Continuous cultivation.
7. Continuous fermenter
Continuous fermentation represents an open system i.e. the
system where nutrient addition and product harvesting is a
continuous process. As against this batch cultivation represents
a closed system, where every thing is added once and only gases
are allowed to exchange from environment in between.
Continuous fermentation is also a submerged kind of process
where organism present in a steady state i.e. log phase. This can
be achieved by continuous addition of fresh nutrients and
harvesting the fermented broth at the same time.
The above process can be handled using Chemostat and
Turbidostat
8. Advantages of Continuous fermenter
Size of the fermenter reduced and hence establishment
expenditure.
Inoculum is to be developed once
Low shut down period
Product is more uniform
Useful where high nutrients or high product accumulation is
inhibitory for the growth
Effective use of manpower
9. Tubular fermenter/ Packed bed reactor
The performance of Batch & CSTF is dominated by suspended
microbes. They often occur as large flocs.
In tubular fermenter the microorganisms exists as flocks or
films.
Process with microorganisms adhering to support surface are
chiefly used in the waste water treatment industry under the
name “Trickling Filter”.
Vinegar, waste water treatment
11. The Fluidized Bed Fermenter
It represents particulate fluidization.
This is a characteristic of beds of regular particles suspended in
an up flowing liquid stream.
It has increase in porosity from bottom to top of the bed &
decreased particle movement when compared with beds
containing particles of constant size.
Used for Beer & Cider production.
Flow rate limited by wash out.
13. Tower fermenter/ Air lift fermenter
It is developed for continuous production of beer.
The fermenter consists of a vertical cylinder with an aspect ratio
of approx.10:1
The significant feature of tower is the progressive & continuous
fall in the specific gravity of the nutrient medium between the
bottom & top of tower.
It is difficult to control microbial hold up.
16. Solid substrate fermentation (SSF)
Fermentation process occurring in the absence or near-absence of
free water.
SSF processes generally employ a natural raw material as carbon
and energy source.
Solid substrate (matrix), however, must contain enough moisture.
Mostly used with fungi.
Examples of products of solid state fermentation include industrial
enzymes, fuels and nutrient enriched animal feeds, Bioleaching,
Bioremediation, Bio pulping etc
17. Advantages of Solid State Fermentation (SSF)
over Submerged Liquid Fermentation (SLF)
The low availability of water reduces the possibilities of
contamination by bacteria and yeast.
High level of aeration can be maintained
Provides natural environment for the growth of Fungi, which is
the main candidate for SSF
The inoculation with spores (fungi) facilitates its uniform
dispersion through the medium
Reactor with simple design is in use
SSF in most cases require low energy
18. Advantages of Solid State Fermentation (SSF)
over Submerged Liquid Fermentation (SLF)
Polluting effluents volume are generally low
The product obtained in SSF have slightly different properties
(thermo tolerance)
Easy downstream processing
19.
20. Disadvantages of Solid State Fermentation (SSF)
over Submerged Liquid Fermentation (SLF)
The substrate in most cases require pre treatment such as size
reduction by grinding, physical, chemical or enzymatic hydrolysis,
cooking and vapour treatment.
Bacteria are poor performer in SSF because of low free water
Monitoring of process parameters such as pH, moisture content,
substrate oxygen and biomass concentration becomes a problem
Agitation is not possible. Aeration is also difficult
Possibilities of contamination with other fungal spp. is always
there
