Current status and advances in the green synthesis of muconic acid.

Muconic acid (MA) is a valuable dicarboxylic acid with three isomers that are extensively utilized in textile and chemical industries. Traditionally, the chemical synthesis of MA consumes nonrenewable petrochemical raw materials and causes significant environmental problems. With the rapid increase in demand for MA, eco-friendly biosynthetic technologies with renewable sources are becoming ideal alternative solutions. This paper systematically reviews recent advances in the biosynthesis of MA isomers, describing not only the mechanism for MA biosynthesis in different microorganisms, including wild and engineered strains, but also focuses on MA production from various renewable resources, especially lignin hydrolysate and lignin-derived aromatics hydrocarbons, such as: benzoic acid, isoeugenol, vanillic acid and phenol. Moreover, cis,cis-muconic acid production from xylose, PET, methane, and glycerol are discussed in detail, providing a much broader substrate spectra and further possibilities for MA large scale industrialization economically. Challenges facing biosynthesis of cis, trans muconic acid and trans, trans muconic acid are discussed finally.