**Author details**

phase are transferred to a small fermenter and later into a larger fermenter with production medium. Several parameters, like medium composition, pH, temperature, and agitation and aeration rate, are controlled. An inducer such as methionine is added to cephalosporin fermentations, phosphate is restricted in chlortetracycline fermentation, and glucose is avoided

**Figure 2.** Chemical structures of actinobacterial secondary metabolites. (a) Staurosporine, (b) octa-valinomycin, (c) methyl-4,8-dimethylundecanate, and (d) N-isopentyltridecanamide from actinobacteria. Source: Cholarajan and

**Secondary metabolites derived**

gramicidin, immunosuppressive cyclosporine

Antibiotics: erythromycin, antiparasitic avermectin antitumor

1. Shikimic acid Ergot alkaloids, antibiotics: candicidin and chloramphenicol 2. Amino acids Antibiotics: penicillin, cephalosporins and cephamycins, and

4. Sugars Antibiotics: streptomycin and kanamycin.

**Table 4.** Intermediate from primary metabolism and their secondary metabolite derivatives.

doxorubicin, taxol

Solid-state fermentation, defined as a microbial culture that develops on the surface and at the interior of a solid matrix and in the absence of free water, holds an important potential for the production of secondary metabolites. Two types of SSF can be distinguished, depending on

in penicillin or erythromycin fermentation.

Vijayakumar [52]; Cholarajan [72]; Thirumurugan et al. [73].

**S. No. Intermediates from primary metabolic pathway**

14 Secondary Metabolites - Sources and Applications

3. Acetyl-CoA and other Kreb's cycle intermediates

*4.5.2. Solid-state fermentation*

Durairaj Thirumurugan1 , Alagappan Cholarajan<sup>2</sup> , Suresh S.S. Raja<sup>3</sup> and Ramasamy Vijayakumar<sup>3</sup> \*

\*Address all correspondence to: rvijayakumar1979@gmail.com

1 Department of Biotechnology, SRM Institute of Science and Technology, Tamilnadu, India

2 P.G. Department of Microbiology, Srinivasan College of Arts and Science, Perambalur, India

3 Research Department of Microbiology, Bharathidasan University Constituent College, Perambalur, India
