Styrene biosynthesis from glucose by engineered E. coli.

Styrene is a large volume, commodity petrochemical with diverse commercial applications, including as a monomer building-block for the synthesis of many useful polymers. Here we demonstrate how, through the de novo design and development of a novel metabolic pathway, styrene can alternatively be synthesized from renewable substrates such as glucose. The conversion of endogenously synthesized l-phenylalanine to styrene was achieved by the co-expression of phenylalanine ammonia lyase and trans-cinnamate decarboxylase. Candidate isoenzymes for each step were screened from bacterial, yeast, and plant genetic sources. Finally, over-expression of PAL2 from Arabidopsis thaliana and FDC1 from Saccharomyces cerevisiae (originally classified as ferulate decarboxylase) in an l-phenylalanine over-producing Escherichia coli host led to the accumulation of up to 260 mg/L in shake flask cultures. Achievable titers already approach the styrene toxicity threshold (determined as ~300 mg/L). To the best of our knowledge, this is the first report of microbial styrene production from sustainable feedstocks.