Improvement of product quality and quantity by manipulating the process.
I-Upstream manipulation (Strain development) The productivity of the wild strains are usually too low for economical processes In general such programs include
•Selection of the biological entities by a screening program to choose the best biocatalyst of the required product.
•Utilization of mutation techniques to prepare mutants of better characters.
•Utilization of recombinant DNA (genetic engineering) to improve an existing process or developing a totally new product.
•Cell fusion for the generation of hybrids with improved productivity.
•Plant cell and tissue culture.
II-Down stream processing
1) Manipulation of the fermentation conditions to specify the product and maximize the yield e.g. changing the oxygen potential of growth for Saccharomycesyields different product.Saccharomyces+ Hexosesaerobic Baker’s yeastSaccharomyces+ Hexosesanaerobic alcoholSaccharomyces+ Hexosesanaerobic & bisulphiteglycerolAlso citric acid production could be performed by surface orby submerged culture (Higher yield).2) Obtaining mathematical models for the fermentation parameters to in the prediction of the best conditions for maximum yield and cost reduction in scaling up of the process.3) Improvement of the efficiency of the biocatalyst by immobilization (discussed later).4) Application of the proper methods for separation and purification of the product e.g. centrifugation, filtration or chromatography.
Fermentation processes
•Fermentation is an industrial process utilizing living cells for the production of commercially valuable products either aerobically or anaerobically.
•In fermentation living cells are allowed to grow under defined conditions in a fermenter(bioreactor). The defined conditions include the use of the proper substrate (medium) and the proper environmental parameters (e.g. temperature, agitation, pH and aeration).
•All must be optimized to achieve the highest yield and quality at the lowest cost possible.
Classification of bioreactors:
1.Configuration:
1.Open
2.Closed
2.Biomass retention mode:2. Immobilized1. Suspended
Methods of fermentation
•Batch fermentation:
•Fed-batch process:
•Continuous Fermentation
–chemostat,or turbidostat.
4. Feeding mode = common methods of fermentation
Scale-up:
It is the transfer of small scale laboratory fermentation to an industrial large scale. Fermentation processes are usually developed in three stages namely laboratory scale(flasks, laboratory fermenters), pilot plant scale(usually 50-200 liters) and production scale
The scheme of fermentation process
preparation Step: Inoculum, medium & bioreactor
Production of the product:5-10% v/v
Recovery of the product:
•In most cases, the product represents a very small fraction of the total fermentation broth and extensive purification procedures must be employed.
•The choice of the operations used in recovery depends on:
•The nature of the desired product
•Concentration
•Stability
•Required level of purity in the end product.•The following are the general methods for concentration and or purification of the product:
–Centrifugation for separation of cells.
–Filtration or sedimentation for separation of cells.
–Precipitation
–Extraction with solvents.
–Chromatography.
–Fractional distillation.
–Ultrafiltration.
–Reverse osmosis and dialysis.
Categories of products
1.Biomass:
2.Enzyme:
3.Metabolites: either primary metabolite such as citric acid which are usually produced during the logarithmic phase of growth (trophophase) or secondary metabolites such as antibiotics, alkaloids or glycosides which are produced during the stationary phase (idiophase).
4.Biotransformation product:
5.Biodegradation product:
6.Immunological product:
7.Energy: alcohol, methane (biogas).
8.Genetically engineered therapeutic protein:
9.Intra or extracellularaccumulation of metals.
10.Plant tissue culture: cell suspension, callus and hairy root.