(388c) Pathway Engineering for the Biosynthesis of Styrene From Renewable Resources In Escherichia Coli

Styrene, an important commodity chemical, possesses versatile commercial applications and is commonly used as a monomer building block for the production of many useful polymers and co-polymers. Being of petrochemical origin and the exorbitant amount of energy required for the chemical synthesis of styrene, a renewable method to produce styrene is invaluable. Utilizing metabolic pathway engineering techniques, a de novo pathway has been constructed to produce styrene from renewable feedstocks. The immediate precursor to the pathway, L-phenylalanine, is endogenously synthesized from glucose (a renewable resource) using the native shikimic acid pathway. L-phenylalanine is then converted to styrene through the co-expression of a phenylalanine ammonia lyase and a trans-cinnamate decarboxylase. Candidate isoenzymes from a variety of  genetic sources, such as bacterial, yeast, and plant, were screened for function for each pathway step. Using an E. coli host platform, achievable titers for shake flask cultures grown in glucose minimal media were determined to be approximately 300 mg/L, which is closely approaching the toxicity threshold of styrene. Methods for overcoming the toxicity barrier through product removal processes including gas stripping and solvent extraction are being explored. Further strategies aimed at enhancing metabolite flux by improving the availability and utilization of the precursor L-phenylalanine will be presented and discussed.