Biotransformation of lignin into 4-vinylphenol derivatives toward lignin valorization

As the most abundant renewable aromatic resource, lignin is an ideal precursor for the production of aromatic fine chemicals. Biotransformation of lignin into 4-vinylphenol (4VP) derivatives holds the promise to contribute to a lignin-based economy. However, the limited bioavailability of lignin and the absence of an effective biotransformation route for lignin to 4VPs have hindered the valorization of lignin and the production efficiency of 4VPs. This review aims to explore an atom-economic biotransformation route for lignin to 4VPs by summarizing the state-of-the-art technologies involved in the entire process, from upstream to downstream. Effective depolymerization technologies have enabled the generation of favorable lignin-derived aromatic precursors for the biosynthesis of 4VPs. Additionally, these technologies also yielded oligomers or monomers that can serve as carbon sources for the cell growth of host strains. Furthermore, the exploration of key enzymes and the construction of effective microbial cell factories have facilitated the assimilation of lignin derivatives and resulted in improved yields and titers of 4VPs. Emerging technologies have further enhanced the biotransformation of lignin by regulating metabolism efficiency, improving the stability and activity of key enzymes, and mitigating inhibitory effects. Overall, by harnessing the inherent aromatic value of lignin, the biotransformation of lignin-derived aromatic precursors into 4VPs offers a promising and sustainable route for 4VPs biosynthesis and lignin valorization. This approach aligns with the atom-economic concept and holds great potential. Biological valorization of lignin toward various high-value products can effectively reduce the dependence on petroleum-based resources and contribute to building a renewable carbon cycle system.