Sustainable production of novel biomaterials in Escherichia coli

Synthetic biological engineering can be used to program microorganisms to perform a variety of functions such as producing new chemicals, aiding in healthcare, and environmental cleanup. In this study, two biomaterials were produced in Escherichia coli: polyhydroxybutyrates (PHBs) and spider silk. While production of biomaterials can be optimized using synthetic biological engineering, one of the bottlenecks to mass production of bioproducts is the cost of the carbon substrate. This study coupled synthetic biological engineering with inexpensive carbon substrates for production of biomaterials.;Currently, there is a need to reduce the dependence on petroleum-derived commodities and a move towards renewable products. PHBs are a group of biodegradable plastics that are produced by a wide variety of microorganisms, mainly as a storage intermediate for energy and carbon. Synthetic biological engineering techniques were used to create export systems for secretion of bioproducts from the cell. PHAs form granules inside bacteria and have associated proteins bound to the granule surface. Phasin, a granule bound protein, was targeted for type I secretion by fusion with a HlyA signal peptide and thereby facilitating indirect secretion of PHAs. To help understand secretion of PHAs, a green fluorescent protein (GFP) was tagged to the PHA polymerase enzyme encoded by phaC. phaC is part of a three-gene cassette that includes phaA and phaB, which are required for PHA production.;Spider silk is a highly versatile biomaterial with a range of potential applications. In this study, spider silk DNA sequences were optimized for production in E. coli and assembly of DNA constructs was carried out with the use of synthetic biological engineering. Specific tRNAs were engineered to be compatible with these spider silk sequences for optimized production.;To address the issue of expensive carbon substrate, a wastewater microalgae extract was used. One of the side streams of microalgae biodiesel production is an aqueous phase that contains simple sugars, ideal for recombinant bacteria growth and bioproduct generation. As a demonstration, PHB production was shown from E. coli grown on an algae-based medium. Coupling synthetic biological engineering with inexpensive substrates could potentially make bioproduct production economically feasible in the future.