Bioprocess 1 Sbt 2132

BIOPROCESS 1 SBT 2132 ROHAIDA CHE MAN 820311-11-5432 HP: 012-9472376 Email: [email protected]

An Introduction to Fermentation Processes

THE RANGE OF FERMENTATION PROCESS • • • • •

Those that produce: microbial cells (or biomass) as the product microbial enzymes microbial metabolites recombinant product Those that modify a compound which is added to the fermentation – the transformation process

Microbial Biomass • The commercial production of microbial biomass may be divided into two major processes: production of yeast to be used in the baking industry production of microbial cells to be used as human or animal food.

Microbial Enzymes • Enzymes have been produced commercially from plant, animal and microbial sources. • Microbial enzymes have the enormous advantage of being able to be produced in large quantities by established fermentation techniques. • Also, it is infinitely easier to improve the productivity of a microbial system compared with a plant or animal one. • The advent of recombinant DNA technology has enabled enzymes of animal origin to be synthesized by microorganisms. • Ex: Sources - Bacterial Enzyme - Amylase Industry - Textiles Application - Desizing of fabrics

Microbial Metabolites • After the inoculation of a culture into a nutrient medium there is a period during which growth does not appear to occur; “lag phase” (time of adaptation). • Log/exponential phase - growth rate of the cells gradually increases the cells grow at a constant and maximum rate. • Stationary phase – growth cease • Death phase – the viable cell number declines

Cont… • Log phase - product produced: growth of the cells, amino acids, nucleotides, proteins, nucleic acids, lipids, carbohydrates. • These products are referred to as the primary products of metabolism. • The phase they are produced (equivalent to the log/exponential phase) – “trophophase”. • Many products of primary metabolism are of considerable economic importance and are being produced by fermentation.

Cont…. • Deceleration and stationary phase – some microbial cultures synthesize compounds which are not produced during the trophophase and which are not appear to have any obvious function in cell metabolism. • These compounds are referred to as the secondary compounds of metabolism. • The phase they are produced (equivalent to the stationary phase) – “idiophase”. • Secondary metabolism may occur in continuous cultures at low growth rates and is a property of slow-growing, as well as non-growing cells.

Recombinant Products • Genes from higher organisms may be introduced into microbial cells such that the recipients are capable of synthesizing foreign proteins. • A wide range of microbial cells have been used as hosts for systems including E. coli, Saccharomyces cerevisiae & fungi. • Products produced by such genetically engineered organisms: insulin, interferon, human serum albumin. • Important factors in the design of these processes:  The secretion of the products  Minimization of the degradation of the product  Control of the onset of synthesis during the fermentation  Maximizing the expression of the foreign gene

Transformation Processes • Microbial cells may be used to convert a compound into a structurally related and financially more valuable compound. • Micro-organisms can behave as:  Catalysts with high positional specificity  Microbial processes are more specific than purely chemical  Removal or modification of functional groups at specific sites on a complex molecule without the use of chemical protection • The reactions which may be catalyzed: dehydrogenation, oxidation, dehydration & condensation, amination. • Microbial processes have the additional advantage over chemical reagents of operating at relatively low temperatures and pressures without the requirement for potentially polluting heavy-metal catalysts. • Ex: production of vinegar (conversion of ethanol to acetic acid).

THE CHRONOLOGICAL DEVELOPMENT OF THE FERMENTATION INDUSTRY

The chronology development of the fermentation industry may be represented as five overlapping stages as illustrated in Table 1.3.

THE COMPONENT PARTS OF THE FERMENTATION PROCESS •Formulation of media to be used in culturing process organism during the development of the inoculum and in the production fermenter •The sterilization of the medium, fermenters and ancillary equipment •The production of an active, pure culture in sufficient quantity to inoculate the production vessel •The growth of the organism in the production fermenter under optimum conditions for product formation •The extraction of the product and its purification •The disposal of effluents produce by the process