Metabolic engineering of bacteria has become a viable technique as a sustainable and efficient method for the production of biochemicals. Two main goals were explored: investigating styrene tolerance genes in E. coli and engineering cyanobacteria for the high yield production of L-serine. In the first study, genes that were shown to be highly differentially expressed in E. coli upon styrene exposure were further investigated by testing the effects of their deletion and overexpression on styrene tolerance and growth. It was found that plsX, a gene responsible for the phospholipid formation in membranes, had the most promising results when overexpressed at 10 µM IPTG, with a relative OD600 of 706 ± 117% at 175 mg/L styrene when compared to the control plasmid at the same concentration. This gene is likely to be effective target when engineering styrene- and other aromatic-producing strains, increasing titers by reducing their cytotoxicity.In the second study, the goal is to engineer the cyanobacterium Synechococcus sp. PCC 7002 for the overproduction of L-serine. As a robust, photosynthetic bacteria, it has potential for being used in such-rich states to capture CO2 and produce industrially relevant products. In order to increase L-serine titers, a key degradation gene, ilvA, must be removed. While ilvA is responsible for degrading L-serine into pyruvate, it is also responsible for initiating the only known pathway for the production of isoleucine. Herein, we constructed a plasmid containing the native A0730 gene in order to investigate its potential to restore isoleucine production. If functional, a Synechococcus sp. PCC 7002 ΔilvA strain can then be engineered with minimal effects on growth and an expected increase in L-serine accumulation.

Cyanobacteria have the potential to efficiently produce L-serine, an industrially important amino acid, directly from CO2 and sunlight, which is a more sustainable and inexpensive source of energy as compared to current methods. The research aims to engineer a strain of Cyanobacterium Synechococcus sp. PCC 7002 that increases L-serine production by mutating regulatory mechanisms that natively inhibit its production and encoding an exporter. While an excess of L-serine was not found in the supernatant of the cell cultures, with further fine tuning of the metabolic pathway and culture conditions, high titers of L-serine can be found. With the base strain engineered, the work can be extended and optimized by deleting degradation pathways, tuning gene expression levels, optimizing growth conditions, and investigating the effects of nitrogen supplementation for the strain.