Bioreactors

bioreactors brief structure

1. Bioreactors Design and construction of bioreactor By Deya 4thyear VII th sem M.Sc , integrated biotechnology SPMVV.

2. BIOREACTOR Bioreactor is a vessel for the growth of microorganisms( fermentation). Bioreactors provide the aseptic condition for fermentation by not permitting contamination. A bioreactor can be defined as an apparatus, such as a large fermentation chamber, for growing organisms such as bacteria or yeast that are used in the biotechnological manufacture of substances such as pharmaceuticals, antibodies, or vaccines, or for the bioconversion of organic waste.

3. Fermentation Fermentation is a metabolic process that converts sugar to acids, gases or alcohol. It occurs in yeast and bacteria, but also in oxygen-starved muscle cells, as in the case of lactic acid fermentation. Fermentation is also used for the bulk growth of microorganisms on a growth medium, often with the goal of producing a specific chemical product. The science of fermentation is known as zymology.

4. Basic principles of bioreactors design

5. introduction The function of the bioreactor is to provide a suitable environment in which an organism can efficiently produce a target product . Cell biomass Metabolite Bioconversion Product

6. The performance of any bioreactor depends on the following key factors: Agitation rate Oxygen transfer pH Temperature Foam production The design of a bioreactor should consider the following factors: the production organism the optimal operating condition required for target product formation , product value scale of production . capital investment

7. Requirements of Bioreactors The design and construction of bioreactors must keep sterility from the start point to end of the process. Optimal mixing with low, uniform shear. Adequate mass transfer, oxygen. Clearly defined flow conditions. Feeding substrate with prevention of under or overdosing. Suspension of solids. Gentle heat transfer. ability to be sterilized for long term; simple construction; simple measuring, control, scale-up &flexibility; compatibility with up- downstream processes; antifoaming measures.

8. Requirements for bioreactor design The basic points of consideration while designing a fermentor : Productivity and yield Fermentor operability and reliability Product purification Water management Energy requirements Waste treatment Operation should be contamination free

9. Bioreactor design In olden days ,traditional design is open cylindrical or rectangular vessels made from wood or stone. Most fermentations are now performed in close system to avoid contamination. It should be constructed from non-toxic, corrosion-resistant materials. Small fermentation vessels of a few liters capacity are constructed from glass and/or stainless steel. A good fermenter should have: Heat and oxygen transfer configuration Sterilization procedures Fast and thorough cleaning system Proper monitoring and control system

10. Construction of bioreactors

11. Bioreactor construction required: Steel/glass vessel Agitator (impeller) Baffles Sparger (aeration system) Temperature probe PH probe Foam probe Cooling jacket Heating coil Dissolved oxygen Pressure

12. Steel/glass vessel In starting wooden or rock vessels are used for fermentation process, they are lack of aseptic condition. In modren bioreactors glass or steel vessels are used Industrial vessels are constructed of stainless steel(SS304)

13. Aeration & agitation Make uniform suspension of microbial cells in homogeneous nutrient medium and provide sufficient oxygen .

14. Impeller ( agitator) Mounted to a shaft through a bearing in the lid Driven by an external power source or direct drive Direct drive - action varied by using different impeller blades Spining of medium in circular direction

15. By Mixing objectives it achieve Bulk fluid & gas phase mixing Air dispersion O 2 transfer Heat transfer Suspension of solid particles Maintenance of uniform environment throughout the vessel.

16. Basffles Four baffles are normally incorporated into agitated vessels of all sizes to prevent a vortex and to improve aeration efficiency. Baffles are metal strips roughly one-tenth of the vessel diameter and attached radially to the wall. recommended that baffles should be installed so that a gap existed between them and the vessel wall, so that there was a scouring action around and behind the baffles thus minimizing microbial growth on the baffles and the fermentor walls.

17. Sparger (aeration system) A device that introduce air into medium Has a pipe with minute holes (1/64 - 1/32 inch or large) Hole – allows air under P to escape into medium Impeller blades disperses air released through sparger into medium

18. Porous sparger Made of sintered glass, ceramics or metal Used mainly on a large scale fermentors Bubble size produced – 10-100 times larger than pores There is also the problem of the fine holes becoming blocked by growth of the microbial culture.

19. Orificie sparger In small stirred fermentors the perforated pipes were arranged below the impeller in the form of crosses or rings (ring sparger ), approximately three-quarters of the impeller diameter. In most designs the air holes were drilled on the under surfaces of the tubes making up the ring or cross. Sparger holes should be at least 6 mm (1/4 inch) diameter because of the tendency of smaller holes to block and to minimize the pressure drop.

20. Nozzle sparger Modern mechanically stirred fermentors use them Single open or partially closed pipes Ideally, positioned centrally below impeller no clogging of pores

21. Control & monitoring probes In-situ methods are developed to process closer control and monitoring .

22. Temperature probe Maintaining a required temperature for microbial growth is essential for good yield . Fluctuation in temperature may cause damage to microorganisms . Cultivation temperature is normally monitored with an accuracy +/-5*c Temperature affects the solubility and diffusivity of oxygen in the fermentation broth. Measurement rang of 20 upto 180oC Electrode body made of stainless steel and highly measuring sensitivity.

23. PH probe Only sterilizable electrodes are used Electrode body is made of glass Measurement range 0 upto13 High sensitiveness The control of pH values is ensured with the help of peristatic pumps.

24. Foam checking probe The appearing of foam is very undesirable phenomenon, since there is a risk to lose an essential part of fermentation broth. During foaming it is not possible to perform high quality analysis and measurements.

25. Elimination of foam Additional metering of antifoam based on sensor Mechanical metering of foam Probe is inserted through top of bioreactor Stainless steel rod set at a defined levels above the broth surface When foam rises and touched the probe tip ,pump is activated and antifoam is released into bioreactor. Mechanical antifoam devices: Discs Propellers Brushes Hollow cones They are attached to agitator shaft above the broth surface Foam is broken down when it is thrown against the walls of the bioreactors.

26. Cooling jacket Cooling jacket is filled with cool water Water jacket circulates cooling water to remove the heat produced by microbial activity It prevents the denaturation of enzyme It used to cool down the reaction so it can come to optimal condition

27. Heating coil Heat will be produced by the microbial activity and agitation If heat generated by these two process is not ideal for manufacturing process then heat may be provided by Placing fermentor in a thermostatically controlled bath By internal heating coils By silicone heating jacket By circulating hot water around the tank in jacket

28. Pressure Industrial bioreactors are designed to withstand a specific working pressure Pressure measurements are required as a factor of safety It is important to fit the e quipment with devices that sense ,indicate, and control pressure Pressure measuring sensors: Bourdon tube pressure gauge Diaphragm gauge Piezoelectric transducer The correct pressure is maintained by regulatory values controlled by associated pressure gauges

29. Dissolved oxygen Measured by DO probe DO electrodes measured partial pressure of dissolved oxygen Electrodes are made up of stainless steel and high responsitivity Function according to C lark principle In event of low oxygen tension in broth ,and agitator speed is increased.

30. Conclusion It is observed that various bioreactor configurations effect the production rate of fermentation Various factors like vessel shape, agitation, aeration, baffles etc., play major role in productivity There is no bioreactor which can satisfy all the conditions There are other novel approaches are developed to increase productivity of spargers , agitators, as well as various controlling probes in order to improve productivity of bioreactors.