Primary and secondary metabolism

A compound that is formed during the log phase of microbial growth is known as a primary metabolite. Those compounds that are formed at the very late stages of growth or during stationary phase are known as secondary metabolites. As these two definitions overlap there is some confusion over how some microbial products might be classified but   a clear   primary metabolite is alcohol from   Saccharomyces cerevisiae.   Here   the production of alcohol is intrinsically linked to energy production so accumulation of alcohol is parallel with the appearance of biomass.

Several significant industrial bioproducts for example almost all nonrecombinant antibiotics are secondary rather than primary metabolites. To enhance the differences between these and the primary metabolites secondary metabolites are also characterized as:

? Having a nonessential role in growth

? Being dependent on the growth conditions for the production

? Being produced as one of a family of similar compounds example for complex heterocycles differing in methylation

The biochemical pathways of secondary metabolite synthesis tend to be longer than primary. Erythromycin is made through the action of 25 separate enzymes and tetracycline by more than 70.