Despite their diversity, secondary metabolites are all produced from a few key intermediates of primary metabolism, which includes all of the anabolic and catabolic processes that are finely balanced to keep the organism alive. Primary and secondary metabolisms are intimately related, with secondary metabolites depending on precursors and energy generated through primary metabolism. For example, the following scheme may be representative of natural anthraquinone compounds:
Use of Cells for Dye Production
The unique characteristic of the generation of the secondary metabolite (which can be used as dye) presents a scientific and technological challenge; namely, how can one get yields that can be used in a commercial scale when the cell produces these chemicals only under conditions of stress (most probably as a defense mechanism). We will present our approach to this problem in the next section, along with experimental data obtained from research being conducted in one area. Table 1 presents a compilation of natural, green dyes that have been researched and published in open literature.
Table 1 Natural, Green Dyes Produced at Bench-Scale Level
An effective biotechnology solution to manufacture of these and other dyes or dyestuff intermediates will impart the following benefits:
1. The medium in which these plant cells or fungi or bacteria grow contain no expensive or toxic chemicals
2. The process is carried out at low temperature (around 30 C) compared to the fuel-consumingvery high temperatures in the synthetic process
3. The process is typically run at neutral pH as opposed to very high acidic or alkaline conditions in the synthetic process
4. The process is very environmentally friendly and sustainable
However, the key factors are, (i) high yield of the product, and (ii) high purity.