Malaysian Journal of Microbiology (Jan 2005)
Secondary Metabolites Production by Solid-State Fermentation
Abstract
Microbial secondary metabolites are useful high value products with an enormous range of biological activities. Moreover, the past two decades have been a phase of rapid discovery of new activities and development of major compounds for use in different industrial fields, mainly pharmaceuticals, cosmetics, food, agriculture and farming. Many of these metabolites could be produced advantageously in industry by solid–state fermentation (SSF). Two types of SSF can be distinguished, depending on the nature of the solid phase used: 1) Solid cultures of one support-substrate phase in which solid phase is constituted by a material that assumes, simultaneously, the functions of support and of nutrients source; and 2) Solid cultures of two substrate-support phases: solid phase is constituted by an inert support impregnated with a liquid medium. Besides good production performance, two phases systems have provided a convenient model for basic studies. Studies in our laboratory, as well as in others, have shown that physiology of idiophase (production phase) in SSF share several similarities with the physiology in liquid medium, so similar strategies must be adapted for efficient production processes. However, our studies indicate the need to develop special strains for SSF since overproducing strains, generated for liquid fermentation, cannot be relied upon to perform well in SSF. On the other hand, there are important parameters, specific for SSF, that have to be optimized (pretreatment, initial moisture content, medium concentration and aeration). Respiration studies of secondary metabolites SSF, performed in our laboratory, have shown more subtle aspects of efficient production in SSF. This indicates that there are certain particularities of physiology in SSF that represent the point that needs a better understanding, and that promise to generate knowledge that will be the basis for efficient processes development and control strategies, as well as for the methodology to generate hyperproducing strains, particularly suited for SSF.
