The document provides an overview of downstream processing (DSP) in biotechnology, focusing on stages such as solid-liquid separation, concentration, and purification of microbial metabolites. It outlines methods for solid-liquid separation, including flotation, flocculation, filtration, and centrifugation, along with their applications and effectiveness. References to relevant literature on DSP practices and advancements are also included.

1. Downstream Processing : Recovery
of Microbial Cells
Presented by – Deepanshu Banyal
Roll no - MAU23PBT010
Course – MSc Biotechnology
Subject – Industrial Biotechnology
Subject Code – MBT - 303
Presented to – Dr. Rajni Sharma
Department of Biotechnology

2. Content
• Introduction to downstream processing
• Stages in downstream processing
• Solid- liquid separation
o Flotation
o Flocculation
o Filtration
o Centrifugation
• References

3. The extraction and purification of a biotechnological product from fermentation is referred to as
downstream processing (DSP)
The desired products for isolation by DSP are most frequently metabolites which may be present as
follows :
• Intracellular products : Products located within the cells e.g. vitamins, enzymes
• Extracellular products : Products located outside the cells (culture fluids) e.g. most antibiotics
(penicillin, streptomycin), amino acids, alcohol, citric acid, some enzymes (amylases, proteases)
• Both extracellular and intracellular : e.g. vitamin B12, flavomycin
Introduction to Downstream Processing

4. Stages in Downstream Processing
DSP of metabolites is a multistage
operation, and may be broadly
divided into the following stages :
• Solid- liquid separation
• Release of intracellular products
• Concentration
• Purification
• Formulation

5. Solid Liquid Separation
• First step in product recovery is the separation
of whole cells (cell biomass) and other
insoluble ingredients from the culture broth
• Note: If the desired product is an intracellular
metabolite, it must be released from the cells
before subjecting to solid-liquid separation
Several methods are used for solid- liquid
separation are :
oFlotation
oFlocculation
oFiltration
oCentrifugation

6. Flotation
• Gas introduced in liquid broth form bubbles
and solid particles get absorbed on bubbles
• Bubbles rise to the foam layer which can be
collected and removed
• Collector substance (for stable foam
formation) e.g. long chain fatty acids,
amines

7. Flocculation
• Cells (or cell debris) form large aggregates to settle down for easy removal
• Depends on the nature and ionic constituents of the medium
• Flocculating agents (inorganic salt, organic polyelectrolyte, mineral hydrocolloid) can be used

8. Filtration
• Most commonly technique for the
separation of biomass and culture filtrate
• Efficiency of filtration depends on many
factors :
o Size of the organism
o Presence of other organisms
o Viscosity of the medium
o Temperature
Several filters used are :
o Depth filters
o Absolute filters
o Rotary drum vacuum filters
o Membrane filters

9. 1. Depth filters : Composed of a filamentous matrix
such as glass wool, asbestos or filter paper
• Particles are trapped within the matrix and fluid
passes out
• Filamentous fungi can be removed by using depth
filters
2. Absolute filters : These filters have specific pore sizes
that are smaller than the particles to be removed
• Bacteria from culture media can be removed by
absolute filters

10. 3. Rotary drum vacuum filters : These filters are
frequently used for separation of both containing
10-40% solids (by volume) and particles in the size
of 0.5-10µm
• Used for filtration of yeast cells and filamentous
fungi
• As the drum rotates, it picks up the biomass
which get deposited on a cake on the drum
surface. The filter cake can be easily removed

11. 4. Membrane filters : Here, membranes with specific pore sizes can be used
• There are two types of membrane fitration :
o Static filtration
o Cross flow filtration

12. Centrifugation
• Technique of centrifugation is based on the principle of density differences between the particles
to be separated and the medium
• Centrifugation is mostly are used for separating solid particles from liquid phase (fluid/particles
separation)
1. Tubular bowl centrifuge : Simple and small centrifuge commonly used in pilot plants
• Operated at high centrifugal speed
• It can be used both in batch and continuous culture and the solids are removed manually

13. 2. Disc centrifuge : Consists of several discs that separate the bowl into settling zones
• Feed/ slurry is fed through a central tube. The clarified fluid move upwards while the solids settle at the
lower surface
3. Multichamber centrifuge : Modifications of tubular bowl centrifuge, consists of several chambers in
which feed flows in zig- zag fashion
• Centrifugal force is much higher in the periphery chambers, as a result smallest particles settle down in
the outermost chamber
4. Scroll centrifuge or decanter : Decanter is generally used to concentrate fluid with high solid
concentration (biomass content 5-80%)

15. References
• Wang, Y., Ling, C., Chen, Y., Jiang, X., & Chen, G. Q. (2019). Microbial engineering for easy
downstream processing. Biotechnology advances, 37(6), 107365.
• Mehta, A. (2019). Downstream processing for biopharmaceuticals recovery. Pharmaceuticals
from microbes: the bioengineering perspective, 163-190.
• Yellapu, S. K., Kaur, R., Kumar, L. R., Tiwari, B., Zhang, X., & Tyagi, R. D. (2018). Recent
developments of downstream processing for microbial lipids and conversion to
biodiesel. Bioresource technology, 256, 515-528.
• Thavasi, R., & Banat, I. M. (2019). Downstream processing of microbial
biosurfactants. Microbial biosurfactants and their environmental and industrial applications, 16-
27.
• Flickinger, M. C. (Ed.). (2013). Downstream industrial biotechnology: recovery and purification.
John Wiley & Sons.