S30: Styrene Biosynthesis from Renewable Resources

With versatile commercial applications, such as a monomer building-block for the synthesis of many useful polymers and co-polymers, styrene is an important commodity chemical that is solely derived from petroleum feedstocks. Through the de novo design and development of a novel metabolic pathway, we have alternatively shown that styrene can be synthesized from renewable feedstocks, such as glucose. The engineered pathway converts endogenously-synthesized L-phenylalanine to styrene through the co-expression of phenylalanine ammonia lyase and a trans-cinnamate decarboxylase. Candidate isoenzymes for each pathway step were screened for function from bacterial, yeast, and plant genetic sources. Using an E. coli host platform, achievable titers for shake flask cultures grown in glucose minimal media already approaching the toxicity threshold of styrene, which was determined to be approximately 300 mg/L.  Further strategies aimed at enhancing metabolite flux by improving the availability and utilization of the precursor will be presented and discussed as well as methods for overcoming the toxicity barrier. To the best of our knowledge, these works represent the first report of microbial styrene production from sustainable feedstocks.