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Nutraceuticals are natural bioactive compounds, generally found in food, that possess medicinal and health-promoting properties other than the sole nutritional role. Popularity of these structurally and functionally diverse molecules, due to their beneficial effects on human health, has raised the global nutraceutical demand which could not be accomplished by their natural and chemical sources. With the progressive development in techniques for synthetic biology, system biology, genetic manipulations, and genome sequencing, microbes can be engineered to be designed as sustainable, economical, and eco-friendly source of value-added nutraceuticals. Moreover, through system metabolic engineering along with the traditional techniques, both native and non-native producers can be programmed by optimizing indigenous regulatory and metabolic pathway or introducing heterologous metabolic pathway genes to produce commercial level of desired metabolites. In addition to overexpression of rate-limiting pathway genes, competing pathways can also be blocked to increase the precursor molecules and direct the carbon flux towards desired pathway. The major steps for development of a high-performance engineered cell factory include the choice of a safe and robust host organism, the selection of best pathway enzymes from different sources to be overexpressed, and the availability of efficient tools for genetic modification. Several genetically tractable microorganisms like Escherichia coli, Corynebacterium glutamicum, Saccharomyces cerevisiae, and Yarrowia lipolytica have been engineered to produce nutraceuticals like polyunsaturated fatty acids, carotenoids, polyphenols, alkaloids, non-proteinogenic amino acid, and poly amino acids. This chapter focuses on the various metabolic engineering strategies employed to design microbes for the production of some valuable nutraceuticals. |
