Bioreactors - Basic Designing and Types.pptx

Bioreactors - Designing. Types of Bioreactor

1. Bioreactors Submitted by : 21SGM04 , M.Sc. Microbiology Submitted To: DR. K. KAVITHA, Assistant Professor, PG and Research Department of Microbiology, Sadakathullah Appa College (Autonomous), Tirunelveli (Affiliated to Manonmaniam Sundaranar University, Abishekapatti )

2. Definition A bioreactor is a type of  fermentation  vessel that is used for the production of various chemicals and biological reactions.  It is a closed container with adequate arrangement for aeration, agitation, temperature and pH control, and drain or overflow vent to remove the waste biomass of cultured microorganisms along with their products.

3. A bioreactor should provide for the following: Agitation (for mixing of cells and medium),  Aeration (aerobic fermentors ); for O2 supply, Regulation of factors like temperature, pH, pressure, aeration, nutrient feeding, and liquid leveled. Sterilization and maintenance of sterility, and  Withdrawal of cells/medium

4. Bioreactor design The design and mode of operation of a bioreactor are based on the production of an organism, optimum conditions required for desired product formation, product value, and its scale of production. I mprove productivity and provide higher quality products at lower prices.

5. The material used for the construction of a bioreactor must have the following important properties: It should not be corrosive. It should not add any toxic substances to the fermentation media. It should tolerate the steam sterilization process.  It should be able to tolerate high pressure and resist pH changes .   Some bioreactors are designed for small scale fermenters and some for large scale industrial applications from the microbial cell (few mm3) to shake flask (100-1000 ml) to the laboratory-scale fermenter (1 – 50 L) to pilot level (0.3 – 10 m3) to plant scale (2 – 500 m3) for large volume).

6. Principle The bioreactor is the heart of any biochemical process as it provides an environment for microorganisms to obtain optimal growth and produce metabolites for the biotransformation and bioconversion of substrates into desirable products. The reactors can be engineered or manufactured based on the growth requirements of the organisms used.  They can be used for the production of various enzymes and other bio-catalysis processes.

7. Parts of the bioreactor and their function Fermenter Vessel A fermenter is a large cylinder closed at the top and bottom connected with various pipes and valves. The vessel is designed in such a way that it allows to work under controlled conditions.  Glass and stainless steels are two types of fermenter vessels used. The glass vessel - small-scale industries - non-toxic and corrosion-proof. Stainless steel vessel - large scale industries- resist pressure and corrosion.

8. Heating and Cooling Apparatus The fermentor vessel’s exterior is fitted with a cooling jacket that seals the vessel and provides cooling water. Thermostatically controlled baths or internal coils are generally used to provide heat while silicone jackets are used to remove excess heat. A cooling jacket is necessary for sterilization of the nutrient medium and removal of the heat generated during fermentation in the fermentor .

9. Aeration System It is important to choose a good aeration system to ensure proper aeration and oxygen availability throughout the culture. It contains two separate aeration devices ( sparger and impeller) to ensure proper aeration in a fermentor . The stirring accomplishes two things: It helps to mix the gas bubbles through the liquid culture medium and It helps to mix the microbial cells through the liquid culture medium which ensures the uniform access of microbial cells to the nutrients.

10. Sealing Assembly The sealing assembly is used for the sealing of the stirrer shaft to offer proper agitation. There are three types of sealing assembly in the fermenter: Packed gland seal Mechanical seal Magnetic drives Baffles The baffles are incorporated into fermenters to prevent a vortex improve aeration in the fermenters. It consists of metal strips attached radially to the wall.

11. Impeller : Impellers are used to provide uniform suspension of microbial cells in different nutrient mediums. They are made up of impeller blades attached to a motor on the lid. Impeller blades play an important role in reducing the size of air bubbles and distribute them uniformly into the fermentation media. Variable impellers are used in the fermenters and are classified as follows. Disc turbines Variable pitch open turbine

12. Sparger : A sparger is a system used for introducing sterile air to a fermentation vessel. It helps in providing proper aeration to the vessel. The sparger pipes contain small holes of about 5-10 mm, through which pressurized air is released. Three types of sparger are used Porous sparger Nozzle sparger Combined sparger –agitator

13. Feed Ports They are used to add nutrients and acid/alkali to the fermentor .  Feed ports are tubes made up of silicone. In-situ sterilization is performed before the removal or addition of the products . Foam-Control The level of foam in the vessel must be minimized to avoid contamination, this is an important aspect of the fermentor . Foam is controlled by two units, foam sensing, and a control unit. A foam-controlling device is mounted on top of the fermentor , with an inlet into the fermentor .

14. Controlling Devices for Environmental Factors : A variety of devices are utilized to control environmental elements like temperature, oxygen concentration, pH, cell mass, essential nutrient levels, and product concentration. Use of Computer in Fermenter : For an efficient process, monitoring, and data collecting, fermentors are generally coupled with modern automated and semi-automated computers and databases.

15. Types Continuous stirred tank bioreactor Bubble column bioreactor Packed bed reactors Fluidized bed bioreactors Photobioreactor Membrane bioreactor Rotary drum bioreactor Immobilized cell bioreactor Activated sludge bioreactor

16. Stirred tank bioreactors Stirred tank bioreactors, also known as stirred tank fermenters, are bioreactors that are designed to hold and mix a liquid culture of microorganisms or cells. They typically consist of a cylindrical tank with a stirrer or impeller to mix the contents and provide oxygen for respiration. Some key features of stirred tank bioreactors include: Agitation Temperature control   pH control   Aeration Sterilization Monitoring and control   Scalability

17. Advantages of Stirred Tank Bioreactors Continuous operation. Excellent temperature control. It is easy to adapt easily to easily adapt to. The simplicity of construction Flexible and low operating (labor) costs and investment requirements. Disadvantages of Stirred Tank Bioreactors The requirement for bearings and shaft seals. Limitation of size by motor size as well as shaft length and weight. The problem of foaming can be a major one. Power consumption is increased because of the Mechanical pressure pumps.

18. Bubble column bioreactor The ratio for height-to-diameter is usually between 4-6. Gas is sucked at the bottom by perforated pipes or plates , or metal spargers with porous materials. O2 transfer, mixing , and other performance parameters are affected mostly by the gas flow rate as well as the characteristics of the gas. Mixing and mass transfer could be improved by putting perforated plates, or baffles with vertical sides within the vessel.

19. Advantages of Bubble column bioreactors  High volumetric efficiency and outstanding heat management. Greater utilization of the plate’s area as well as flow distrubution . Self-regulating. Disadvantages of Bubble column bioreactors  Inefficient compared to other bioreactors. Doesn’t have draft tube A higher consumption of catalysts that the bed fixed Installation costs are higher, and the design is difficult to create

20. Packed bed reactors A bed of particles are confined in the reactor. The biocatalyst (or cell) is immobilized on the solids which may be rigid or macroporous particles. A fluid containing nutrients flows through the bed to provide the needs of the immobilized biocatalyst. Metabolites and products are released into the fluid and removed in the outflow. The flow can be upward or downward.

21. Advantages of Packed Bed Reactors Higher conversion per unit mass of catalyst than other catalytic reactors Low operating cost. Continuous operation. No moving parts to wear out. Catalyst stays in the reactor. Reaction mixture/catalyst separation is easy Design is simple Effective at high temperatures and pressures Disadvantages of Packed Bed Reactors Undesired heat gradients. Poor temperature control. Difficult to clean. Difficult to replace catalyst. Undesirable side reactions.

22. Fluidized bed bioreactors Suitable for reactions involving a fluid-suspended particulate biocatalyst such as immobilized enzyme and cell particles. The properties include: Extremely high surface area contact between fluid and solid per unit bed volume High relative velocities between the fluid and the dispersed solid phase. High levels of intermixing of the particulate phase. Frequent particle-particle and particle-wall collisions.

23. Advantages of Fluidized Bed Bioreactor Uniform Particle Mixing Uniform Temperature Gradients Ability to Operate Reactor in Continuous State Disadvantages of Fluidized Bed Bioreactor Increased Reactor Vessel Size Lack of Current Understanding Erosion of Internal Components Pressure Loss Scenarios

24. Photobioreactor Photobioreactors are utilised for the photosynthetic cultivation of microalgae and cyanobacteria to produce astaxanthin and β-carotene, among other products. Photosynthetic cultures require either natural or artificial light. However , excessive light induces photoinhibition ; in this case, a little reduction in light intensity will increase the rate of photosynthesis. As cell population increases, the self-shading effect of cells further restricts light penetration.

25. Advantages of Photobioreactor Higher productivity Large surface-to-volume ratio Better control of gas transfer. Reduction in evaporation of growth medium. More uniform temperature. Disadvantages of Photobioreactor Capital cost is very high. The productivity and production cost in some enclosed photobioreactor systems are not much better than those achievable in open-pond cultures. The technical difficulty in sterilizing

26. Membrane bioreactor Membrane bioreactors (MBR) are been used since 90s. It basically combines traditional treatment system with filtration via membranes resulting in removal of organic and suspended solid matters that also removes high level of nutrients. Membranes in the MBR system are submerged in an aerated biological reactor. The pore size of the membrane ranges from 0.035 microns to 0.4 microns. However, membrane fouling is a chief obstacle to the extensive application of MBRs. Moreover large-scale use of MBRs in waste water treatment will involve a notable worthy decrease in price of the membranes

27. Advantages The loss of enzyme is reduced. Enzyme lost by denaturation can be made up by periodic addition of enzyme. Substrate and enzyme can be easily replaced.

28. Rotary drum bioreactor The rotating-drum bioreactors comprise a horizontally rotating drum, that may or may not have a paddle mixer and rotates slowly for proper mixing of fermentation substrate. For scaling-up purposes, many assumptions need to be made concerning the rotating-drum bioreactors. The bioreactor is cylindrical (with a length L and diameter D) and partially filed;

29. Advantages of Rotary Drum Reactor High oxygen transfer. Good mixing facilitates better growth Disadvantages of Rotary Drum Reactor: Difficult to scale up.

30. Immobilized cell bioreactor The immobilized cell reaction (ICR) operates in accordance with the principle of immobilization. The process of limiting the cell’s mobility within a certain space. The interaction between hydrogen and hydrophobic and the formation of salt bridges between the adsorbent as well as the cells are the driving factors for immobilization. In general, immobilization can be divided into two kinds which are passive and active. In the passive model  cells, they are stuck naturally in the matrix of solids, leading to the creation of biofilm. In active techniques  Immobilization can be induced by a physical or chemical method. This can occur in a variety of ways like attachment, entrapment gathering, and confinement.

31. Advantages: The harvesting of the product you want is a breeze and requires any effort if the substances are released in the medium Disadvantages There are some restrictions in the ICR like; A limitation in mass transfer due to the intraparticle diffusion resistance, which restricts the ability of the substrate to get to cells. This type of problem occurs in aerobic reactions, where there is an oxygen shortage to cells, resulting in lower reactor performance. Another issue is inhibition of the product in which the concentration of the product is reduced within the inner core and, consequently, the rate of reaction is also decreased.

32. Activated sludge bioreactor When an active sludge bioreactor is used the proportion of microbes as well as the amount of oxygen and substrate are all the same as the reactor is equipped with a homogeneous tank in which the feed is dispersed throughout the. In the active sludge with plug flow, the reactor has an extended channeled inlet which restricts any growth in microorganisms as well as improves the ability of sludge to settle . In the process of activated Sludge, sewage with organic matter is pumped to the tank for aeration that is then metabolized because it is filled with microorganisms. The organic matter that is metabolized is converted to CO2 and water in order to generate energy. A portion of the cells that have formed during the process are eliminated from the process in sludge. The remaining sludge returns to an aeration tank in which this process is carried on.

33. Application The reactor is employed in the treatment of wastewater and sewage. This particular reactor is used to produce biofuels such as biogas, bioethanol and so on. such as biofuels that are made by milk-based waste. Advantage: The reactor can be operated with high organic loading rates. Limitation: This reactor is a major consumer of energy and also capital, The operating expenses are high.