SS bioreactors are large fixed vessels of stainless steel that provide optimal conditions for biological systems. They require steam sterilization between uses. SUBs are pre-sterilized single-use bags installed in reusable frames that control temperature. SUBs have reduced capital costs due to eliminating cleaning and sterilization steps between batches, allowing more frequent production. However, SUBs present challenges including higher bioreactor failure rates and less developed regulatory compliance compared to SS bioreactors. The choice between SS and SUB depends on factors like safety, cost-effectiveness, operational efficiency, and application.

1. Disposable Bioreactors versus Stainless Steel Bioreactors
Bioreactors are defined as vessels where biological reactions take place in an
optimum external environment provided to meet the need of biological system which
includes enzymes, Viruses, microorganisms, animal or mammalian cells, plant cells and
tissues. Designing a specific bioreactor to cater the needs of a particular biological system
requires intensive knowledge of studies on genetic expression of a microbe, biochemistry
and chemical reactions in and out the cell, physical conditions for optimum growth and
division of a microbe along with the metabolism involved. Dissolved oxygen
concentration, concentration of metabolites pH, temperature, Agitation rate, mixing, and
supplementation of nutrients , rate of removal of product or toxins , media design, all need
to be controlled and optimized for required production. With this understanding of the
biological system and its requirements on its physical and chemical environment, a proper
bioreactor type can be chosen. Among the bioreactor types available for a certain
bioprocess, it is important to have a balanced consideration of many factors like oxygen
transfer, mixing, shear, operational stability and reliability, scale-up, and cost. The chosen
bioreactor should be further characterized and the operational mode should be optimized.
In order for a strategic manufacturing in biopharmaceutical companies, no argument in
terms of safety, cost-effectiveness, or operational efficiency is fully convincing to choose
one technology platform or the other for all applications. Over the time new technology
has taken over the traditional stainless Steel (SS) bioreactors and have rightly gained
wide acceptance in the biopharmaceutical industry. On the basis of ease and new
strategies implemented in bioreactors, it can be categorized into types:
1. Traditional Stainless Steel (SS) bioreactors
2. Single Use or Disposable (SUB) Bioreactors
Following are the factors that differentiate & contrast between the two bioreactors that are
widely used in bioprocess engineering –
1. Definition:
SSB: A large fixed vessel of stainless steel and other metals that provide optimum
conditions for a biological system is known as SS Bioreactor. These bioreactors
can be Membranes bioreactors, fluidized bed bioreactors, stirred-tank bioreactors,
packed bed reactors that utilize a metal framework within which growth and
production of microbes occur.
SUB: A typical single-use bioreactor consists of a pre-sterilized, disposable, single-
use bioreactor bag of multilayer polymeric composition, which is installed within a
reactor frame that provides temperature control and is integrated with a controller.
The types of bioreactors include cylindrical and square stirred tanks, orbital
shaken, and air-driven.

2. 2. Volume:
SSB: Vessel sizes from one liter to 30,000 liters
SUB: Most disposable bioreactor applications to date have been with cell culture
processes with reactor offerings up to 2000-L scale with a range of turn-down
ratios (up to 1:5), which allow flexible working volume selections.
3. Shape of Bioreactor:
SSB- Most glass and stainless steel bioreactor vessels are cylindrical with concave
or dished heads. This is the standard geometry for most conventional Bioreactors.
SUB- mostly cubical shaped bio-containers are available. Also designers have the
opportunity to consider alternative geometries.
4. Pre-sterilization :
SSB: high-pressure steam for sterilization is utilized every time it is operated hence
bioreactors are designed with rounded shape for enhanced mechanical stability.
Expensive automation required to operate clean-in-place and sterilize-in-place
procedures
SUB: The end user receives the pre-sterilized gamma-irradiated reactor bag
assembled with the relevant sparger tubes, sampling ports, and magnetic coupled
impeller
5. Capital cost:
SSB: steam-in-place (SIP) and clean-in-place (CIP) procedures are required and
hence can account for up to 70% of automation costs and is a significant footprint
to the stainless-steel bioreactor.
SUB: elimination of clean and steam procedures reduces the turnaround time
between batches, enabling more batches per year and increased facility use. An
analysis showed the turnaround time for single-use bioreactors to be at least three
times faster than for conventional stainless steel.
6. Regulation:
SSB: More advanced measurement and control systems.
SUB: quality control and regulatory compliance are less well developed.
7. Failures:
SSB: Risk of contamination is high, No risk of leakage
SUB: End users experience unacceptable bioreactor failure rates owing to a range
of issues such as seam failures, film punctures, and handling errors. Additional
work is needed to improve robustness, training, and transport packaging. The

3. bioreactors are designed to enable complete installation and inflation by no more
than two operators, with step-by-step instructions and color-coded numbered
labels to guide them through the process. Minimal operator intervention also
reduces the risk of accidental damage.
8. Method of sterilization for Bioreactor:
SSB: sterilized by steam at high pressure
SUB: pre-sterilized by radiation or treatment with ethylene oxide and disposedafter
use.
9. Heat & O2 transfer :
SSB: heat transfer is efficient than that in SUB through thermal jacket.
SUB: the insulating plastic material of the reactor bag blocks efficient heat transfer
thus reducing the effect of the thermal jacket. High oxygen transfer rates and short
mixing time can be achieved due to direct bottom-driven impellor.
10.
11.
Single Use Bioreactor -
Agitated Type
Design for Single-use
Bioreactors