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BIOREACTION AND BIOREACTOR

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## BIOREACTION AND BIOREACTOR

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**BIOREACTION AND BIOREACTOR**By: Mdm. Noor Amirah Abdul Halim**WHAT IS BIOREACTOR?**• A special reactor that sustains and supports life for cells and tissue cultures. • Used in industrial processes to produce pharmaceuticals, vaccines, or antibodies • Bioreactors are commonly employed in the food and fermentation industries, in waste treatment, and in some biomedical operations - the heart of any industrial fermentation process. • The advantages are mild reaction conditions, high yields and stereospecific compounds. • Bioreactors supply a homogeneous (same throughout) environment by constantly stirring the contents. • Bioreactors give the cells a controlled environment by ensuring the same temperature, pH, and oxygen levels.**THE CELL**• A cell uses its nutrients to produce energy and more cells. • The cell consists of a cell wall and an outer membrane that encloses cytoplasm containing a nuclear region and ribosomes. • The cell wall protects the cell from external influences. • The cell membrane provides for selective transport of materials into and out of the cell**CELL GROWTH**• The growth of an aerobic organism follows the equation; SUBSTRATE**RATE LAW FOR BIOREACTOR**• The most commonly used expression is the Monod equation for the exponential growth • The specific growth rate can be expressed as; • Thus,**RATE LAW FOR BIOREACTOR**• For most of the bacteria, Ks is small ( ) Thus, it can be neglected to give; Growth rate, rg depends on the nutrient concentration (Cs)**INHIBITION OF THE GROWTH RATE (rg)**• In many systems, product inhibits the growth rate. • Wine production is an example where fermentation of glucose to produce ethanol is inhibited by the product ethanol (ethanol kills the yeast)**TESSIER AND MOSER EQUATION**• Tessier & Moser equations are another equation used to describe the cell growth rate. They fit the experimental data better. • 𝜆 and k are empirical constants TESSIER MOSER**CELL DEATH RATE (rd)**• The cell death is a result of; - harsh environments - depletion of nutrients - presence of toxic substance • The rate law for cell death is given by;**EFFECT OF TEMPERATURE**The cell growth at temperature =T**RATE OF PRODUCT FORMATION (rp)**• Product formation can take place during different phases of the cell growth cycle. When product formation only occurs during the exponential growth phase, the rate of product formation is:**Batch operation**Cell**Substrate**Growth phase stationary phase**DESIGN EQUATION**• CSTR (chemostat) The case where the volumetric flow rates in and out are the same and no live cells enter the chemostat • Dilution rate Dilution rate is a parameter used in bioreactor. It is reciprocal of space time**CSTR Mass Balance**• Using Monod Eqn;the growth rate,rg**For steady state operation;**• Mass flowrate of cells out of the system, Fc Divide by Cc V, Neglect death rate The specific growth rate of the cell can be controlled by the dilution rate,D**From Monod Equation,**• If a single nutrient is limiting, • - cell growth is the only process to substrate consumption. • cell maintenance is neglected. • Then,**WASH OUT**To learn the effect of increasing the dilution rate; Assume; the dilution rate at which wash-out will occur is:**D for the maximum cell production:**{Cell production per unit volume is the mass flow rate of cells out of the reactor} :**Exercise**Cell growth takes place in bioreactors called chemostat. A substrate such as glucose is used to grow cells and produce a product which is CO2. Glucose cell More cells + CO2 By assuming 1 mole of glucose (180g/dm3) reacts, to produce 0.909 mol/dm3 of cells (MW: 91.34 g/mol) and 1.47 mol/dm3 of CO2 Calculate: • The yield coefficient YC/S • The yield coefficient , Y c/p • The rate of cell growth rg ( k = 1.3 h-1 and μmax = 2.2 x 10-5 s-1) • The rate of product formation, rpduring the exponential growth • The rate of substrate consumption (-rs) during the exponential growth (m = 0.05 h-1)