Mdm Norasyikin Chapter 1.1

1.2 I N T R O D U C T I O N TO FERMENTATION

 The term fermentation can be used to describe any process involving the production of organic products by the mass culture of a microorganism (bacteria, yeast and fungi).

Unbaffled flask

Fermentation using  recombinant  microorganism

The four groups of commercially  important fermentation using  normal microorganisms are; 

A microorganisms  foreign product:  referred to as a  product  from  recombinant DNA  technology or  genetically engineered  strain, i.e.  recombinant strain  (eg., insulin, vaccines,  interferon, human  protein, erythropoitein  - epo)

(ii) production of microbial cell  (biomass),  (iii) production of microbial enzymes,  (iv) production of microbial  metabolites, and  (v) transformation processes - to  modify a compound which is  added to the fermentation (eg.,  certain amino acids and fine  chemicals)

Fermentations can be carried out either  as submerged (liquid medium) or solid  state (solid or semi solid medium)  fermentation process. 

More than 90% of industrial processes  are carried out as submerged  fermentation 

A generalized schematic representation of a typical  submerged fermentation process 

•Main industrial equipment required for  the fermentation process is large scale  aseptic fermentation vessel which is  termed as the fermenter or bioreactor. 

•Main function of a fermenter is to 

provide a controlled environment for the  growth of a microorganism to obtain a  desired product. 

•Fermenter should be capable for being 

operated aseptically for a number of days  and should be reliable in long-term  operation. 

•For aerobic fermentation, adequate 

aeration and agitation should be provided  to meet the metabolic requirements of the  microorganism. However, the mixing  should not cause damage to the  microorganism. 

INDUSTRIAL BIOREACTORS There may be biological waste treatment in larger vessels, but the world’s largest fermenter is shown in these photos taken from Chemical and Engineering News. The fermenter is shown in 200 ft high and 25 ft diameter.

The success of a  fermentation depends  upon the existence of  defined environmental  conditions for biomass  and product formation.  Thus temperature,  pH, degree of  agitation, oxygen  concentration in the  culture and other  factors may have to be  kept constant during  the process.  The provision of such  conditions requires  careful monitoring of  the fermentation so  that any deviation  from the specified  optimum might be  corrected by a control  system. 

Typical Microbial growth phases

The fermenter could also be operated in different modes aims at  improving the performance.

BATCH FERMENTATION

Considered to be a closed system. At time t=0 the sterilized nutrient solution in the fermenter is inoculated with microorganisms and incubation is allowed to proceed. In the course of the entire fermentation, nothing is added, except oxygen (in case of aerobic microorganisms), an antifoam agent, and acid or base to control the pH. The composition of the culture medium, the biomass concentration, and the metabolite concentration generally change constantly as a result of the metabolism of the cells.

FED BATCH FERMENTATION Substrate is added in increments as the fermentation progresses. In the fed-batch method the critical elements of the nutrient solution are added in small concentrations at the beginning of the fermentation and these substances continue to be added in small doses during the production phase.

CONTINUOUS FERMENTATION

An open system is set up. Sterile nutrient solution is added to the bioreactor continuously and an equivalent amount of converted nutrient solution with microorganisms is simultaneously taken out of the system.

Feed  medium  reservoir Productivity = (F/V) x Product  concentration in outflow

Fi V Fo Outflow  containing  product

Continuous Fermentation Fresh growth medium is added continuously during fermentation and spent medium is removed. Fermentation can last up to 1,000 hours.

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