Fed-Batch Culture Maintenance Coefficient

Introduction

“Fed-batch culture” is a widely used technique  for controlling substrate intakes by cells and also helps to perform a cell regulation by using control operation culture technique.. Specific rate of substrate uptake from a medium for maintenance activity is known as maintenance coefficient. Unit for calculating the maintenance coefficient is Kg. maintenance includes the energy cost of osmoregulation cell motility and other metabolic reactions in cells. Maintenance coefficient is used to define a specific rate of substrate intake and the formula of this is “m= [dS/dT] m/X”.

Fed-batch culture maintenance coefficient

In Fed-batch culture is a semi-open system where nutrients are added and volume of liquor culture increases as systematically added to culture. Fed-batch culture is a more controlled and sequential addition of nutrients that enables higher cell densities. There are many advantages of Fed-batch culture that includes long-term synthesis of products, increased cell numbers and number of products. A number of products proportional to biomass help to achieve greater efficiencies. With controlled and sequential action Fed-batch increases the productivity of nutrients. 

It also allows bioreactors to be used for the production of non-profitable periods. Catabolite repression and crabtree effect in Fed-batch can be managed by limiting the concentration of substrates. Broth viscosity can be reduced, if necessary, it also helps in evaporation that replaces water loss. “Maintenance coefficient” is also known as “Specific substrate consumption rate”. An important role of the maintenance coefficient includes the energy supply rate that is essential for maintaining the life function of non-growing cells. It helps to maintain physiological reactions such as osmoregulation, rebuilding or denaturing proteins and sensory or tactile movement of cells. Units that are generally used to denote maintenance growth rates are mol ATP/ cell/ hour and mostly used gm substrates/gm biomass/ hour. 

What is fed-batch culture

Fed-batch culture is a modified culture or an intermediate batch that provides continued fermentation techniques. Fed-batch is a population method for the industrial fermentation process that supplements nutrients to the bioreactors. Supplement of nutrients to bioreactors in specific intervals helps to obtain a high density of biomass thus it is a semi-continuous system that remains in bioreactors until substrates are added in small amounts through processes. Fed-batch allows intermittent or continuous feeding of substrates during culture broth fermentation. In this process, no culture media is removed until the process is finished. Due to periodic addition of nutrients volume inside the culture vessel increased. It provides a controlled operation that limits nutrition increments and always neglects maximum growth rates. High cell density in Fed-batch culture produces more metabolites and results in high productivity. 

Addition of relative dilutes substrates initiates the process of Fed-batch culture. After batch time production within culture vessels are harvested. In Fed-batch Culture volume remains constant. The variable volume of Fed-culture keeps changing with the due time of fermentation. It prevents catabolite repression; catabolism is simple products after the breakdown of complex products and this process is known as “Catabolism”. “Repression” is a mechanism that synthesises a specific enzyme, thus metabolites that repress enzymes and their activities are known as Catabolite repression. Examples of Catabolic reactions include Lactose-operon in E.coli; it doesn’t take up lactose when glucose is present inside the cell. 

Fed-batch culture 

Fed-batch Culture is used for the production of antibiotics such as drugs formed using penicillin that requires control feeding of nutrients or substrates. Controlling of intake of substances is important as underfeeding or overfeeding of substrates results in starvation and dilution of products. Thus Fed-batch provides a controlled flow of nutrition and results in control growth of the cell and desire to obtain a high density of the cell. Fed-batch culture is used heavily in industries for production of Saccharomyces cerevisiae also known as baker’s yeast. Several benefits of this technique include it provides control over feed flow during fragmentation and helps in overcoming conditions of catabolic repression. Replace water loss with evaporation. Major advantages of Fed-batch Culture include lower operation cost than batch fermentation and also loss velocity of broth.

Fixed volume fed-batch culture

Fixed volume fed-batch culture is a limiting substance that is fed without liquified solutions.Substances can be added to cultures added by dialysis. This provides a constant rate and also produces a huge mass of biology of living cells that is constant during the fermentation time. Fixed volume Fed-Batch Culture is used for “hyperthermophilic Archaebacteria cultivation”.  That helps to achieve an almost constant volume of culture and limiting substances for the growth of cells. This procedure is associated with feeding limiting substances to reactors that are very concentrated and resulting in a notable increase in volume.

Conclusion 

Many disadvantages of Fed-batch include it requires technical skills for maintenance and operation and that makes it a complex process. This culture prevents nutrition from becoming a limiting factor by supplying substrates at sequential intervals.  Maintenance coefficients help to measure the up taking of substrates from a medium. Fed-batch fermentation is an advanced technique rather than batch fragmentation. Fed-batch overcomes limitations of batch culture due to addition of substrates once in a single batch. For culture, it is necessary to study physiology and microbial cells that relate to productivity.