Studies on the environmental fate, ecotoxicology and toxicology of 2-methyl 1,3-propanediol

Biosynthesizing structurally diverse diols via a general route combining oxidative and reductive formations of OH-groups

Diols encompass important bulk and fine chemicals for the chemical, pharmaceutical and cosmetic industries. During the past decades, biological production of C3-C5 diols from renewable feedstocks has received great interest. Here, we elaborate a general principle for effectively synthesizing structurally diverse diols by expanding amino acid metabolism. Specifically, we propose to combine oxidative and reductive formations of hydroxyl groups from amino acids in a thermodynamically favorable order of four reactions catalyzed by amino acid hydroxylase, L-amino acid deaminase, α-keto acid decarboxylase and aldehyde reductase consecutively. The oxidative formation of hydroxyl group from an alkyl group is energetically more attractive than the reductive pathway, which is exclusively used in the synthetic pathways of diols reported so far. We demonstrate this general route for microbial production of branched-chain diols in E. coli. Ten C3-C5 diols are synthesized. Six of them, namely isopentyldiol (IPDO), 2-methyl-1,3-butanediol (2-M-1,3-BDO), 2-methyl-1,4-butanediol (2-M-1,4-BDO), 2-methyl-1,3-propanediol (MPO), 2-ethyl-1,3-propanediol (2-E-1,3-PDO), 1,4-pentanediol (1,4-PTD), have not been biologically synthesized before. This work opens up opportunities for synthesizing structurally diverse diols and triols, especially by genome mining, rational design or directed evolution of proper enzymes.

Diols are important bulk and fine chemicals, but bioproduciton of branch-chain diols is hampered by the unknown biological route. Here, the authors report the expanding of amino acid metabolism for biosynthesis of branch-chain diols via a general route of combined oxidative and reductive formations of hydroxyl groups.