Question

What are the advantages of bioreactor which uses a continuous culture system rather than batch culture?

Answer 1

Bioreactors are closed systems equipped with multiple sensors, motor-driven impellers for agitation, and instruments for temperature control, gassing and thus the provision of liquids. Associated software facilitates online monitoring and control of all relevant process parameters, and sometimes allows for integrated analytics and comprehensive processing furthermore.

Complete answer:
A bio-process consists of; upstream processing, bioreaction and downstream processing to alter the material to a finished product.

Upstream Processing: The staple is either from a biological or non-biological origin. Firstly, it's changed to a more suitable form for processing. This is often completed within the upstream processing stage. This stage involves:
1.Chemical hydrolysis
2.Preparation of liquid medium
3.Parting of particulate
4.Air purification
5.Other preparatory operations

Bioreaction: After upstream processing, the resulting material is moved to at least one or more bioreaction stages. The bioreactors form the bottom of the bioreaction stage. The bioreaction stage consists of three operations:
1.Production of biomass
2.Metabolise biosynthesis
3.Biotransformation

Downstream Processing: For the subsequent stage of the method, the fabric which was created within the bioreactor has to be further processed to alter it to a more useful form. This process comprise of:
1.Solid liquid separation
2.Adsorption
3.Liquid-liquid extraction
4.Distillation
5.Drying

A batch fermentation system- a closed system. Initially, sterilized nutrient solution within the fermenter is inoculated with microorganisms and incubation is allowed t at an appropriate temperature and gaseous environment for an appropriate time. During this nothing is added, except oxygen, an antifoam agent, acid or base to manage pH. The composition of the medium, the biomass concentration and therefore the metabolite concentration generally change constantly as a result of metabolism of the cells. After the inoculation of a sterile nutrient solution with microorganisms and cultivation under physiological conditions is completed. Batch culture systems provide variety of advantages:
Reduced risk of contamination or cell mutation because the growth period is brief.
Lower capital investment compared to continuous processes for the identical bioreactor volume.
More flexibility with varying product/biological systems.
Higher material conversion levels, resulting from a controlled growth period.

Continuous fermentation: In continuous fermentation an open system is about up. Sterile nutrient solution is added to the bioreactor continuously and a similar amount of converted nutrient solution with microorganisms is simultaneously taken out of the system. During a homogeneously mixed bioreactor, we are able to have a chemostat or a turbidostat. Within the chemostat, within the steady state adjusting the concentration of 1 substrate controls cell growth. Within the turbidostat, cell growth is kept constant by using turbidity to observe the biomass concentration and also the rate of feed of nutrient solution is appropriately adjusted. Within the chemostat, a constant chemical environment is maintained, while in an exceedingly turbidostat constant cell concentration is maintained.
In a chemostat the expansion chamber is connected to a reservoir of sterile medium. Once growth is initiated, fresh medium is continuously supplied from the reservoir. The quantity of fluid within the growth chamber is maintained at a continuing level by some style of overflow drain. Fresh medium is allowed to enter the expansion chamber at a rate that limits the expansion of the bacteria. The speed of addition of fresh medium determines the speed of growth because the fresh medium always contains a limiting amount of a necessary nutrient. Thus the chemostat relieves the insufficiency of nutrients, the buildup of toxic substances and therefore the accumulation of excess cells within the culture which are the parameters that initiate the stationary phase of the expansion cycle. There are several major advantages of using continuous cultures as critical batch cultures:

Continuous reactions offer increased opportunities for system investigation and analysis. Because the variables remain unchanged, a benchmark are often determined for the method results, and so the consequences of even minor changes to physical or chemical variables will be evaluated. By changing the growth-limiting nutrient, changes in cell composition and metabolic activity are often tracked. The constancy of the continual process also provides a more accurate picture of kinetic constants, maintenance energy and true growth yields.
Continuous culture provides a better degree of control than a batch culture. Growth rates are regulated and maintained for extended periods. By varying the dilution rate, biomass concentration may be controlled. Secondary metabolite production may be sustained simultaneously together with growth. In steady state continuous culture, mixed cultures are often maintained using chemostat cultures – unlike in a very batch process where one organism usually outgrows another.
Bioreactors operated as chemostats enhance selectivity for thermophiles, osmotolerant strains or mutant organisms with high growth rates. Also the medium composition is optimized for biomass and products formation employing a pulse- and shift method that injects nutrients directly into the chemostat. As changes are observed, the nutrient is added to the medium supply reservoir and a brand new steady state is established.
Because of the steady state of continuous culture, the results don't seem to be only more reliable but also more consistent resulting in a higher quality product.
It also ends up in higher productivity per unit volume, as time consuming tasks, like cleaning and sterilization are unnecessary.
The ability to automate the method makes it more cost-efficient and fewer sensitive to the impact of human error.

Note: 1.Citric acid (citrate) is widely used as a flavour enhancer, a preservative in manufactured foods and an antioxidant. It is produced as an intermediate of the tricarboxylic acid cycle under aerobic conditions.
2.Citric acid is mass produced by continuous fermenter systems from cultures of the fungus Aspergillus niger.