The subject technology generally relates to biosynthesis of styrene. Certain embodiments of the subject technology is based, in part, on the recognition that phenylalanine can be converted to styrene by a two-step pathway of deamination and decarboxylation, with trans-cinnamic acid (tCA) as the intermediate. Two types of enzymes are directly involved in this process, phenylalanine ammonia lyase (PAL), which converts phenylalanine to tCA, and cinnamic acid decarboxylase, which coverts tCA to styrene. Host cells expressing these two types of enzymes can be cultured in bioreactor to produce styrene from renewable substrates such as glucose.