Abstract:
The grand challenge of metabolic engineering lies in the complexity and redundancy of
cellular pathways and the evolutionary drive of a cell to maximize growth rather than a
forced bioengineering objective. Engineering microorganisms to thus produce value
added products from bulk chemicals as carbon source is now greatly accelerated by use of
Synthetic Biology. The fast forwarding evolution has thus uncapped the limits of
engineering biological systems. Rational strain design for production of value added
products requires channeling of basic substrate molecules towards a desirable metabolic
output to make products of interest. When complex pathways are introduced inside the
cell, limitations including intermediate toxicity, low enzyme activity, metabolic burden
(cofactor imbalance etc.) need to be overcome for high performance. Such bottlenecks
can be addressed using pathway engineering that exploits the synergies of synthetic
biology, metabolic engineering and systems biology. Successful metabolic engineering
for platform cell factories to produce a wide range of fuels and chemicals necessitates
identifying the sensitivity of product/process to nutrient precursors and cofactors by
coupling of cellular objectives of growth and energy to desired bioengineering objectives.
This thesis explores the application of these principles to develop scalable systems to
make a drug molecule violacein and a biopolymer Polyhydroxyalkanoates (PHAs).
Violacein is a bacterial bis-indole pigment of commercial interest having antibacterial,
antitumoral, antiviral, trypanocidal and antiprotozoan properties. PHAs form a class of
natural polyesters, commonly referred to as bioplastics, that many organisms accumulate
as intracellular granules to store carbon and reducing equivalents in response to specific
environmental conditions. This thesis discusses the rational strain design and
development in the context of systems metabolic engineering and synthetic biology for
violacein and polyhydroxybutyrate.
