Understanding the Limitations in the Biosynthesis of Polyhydroxyalkanoate (PHA) from Lignin Derivatives

To investigate the conversion of lignin derivatives to biopolyesters, 11 polyhydroxyalkanoate (PHA)-accumulating strains were cultured on mineral salt media containing each of the 18 lignin derivatives and hydroxybenzoic acids, including intermediates derived from the metabolism of lignin derivatives in bacteria. Most of the strains grew poorly in media containing lignin derivatives such as p-coumaric acid, caffeic acid, ferulic acid, and sinapinic acid. One of the strains, Pseudomonas putida Gpo1, grew in the presence of p-coumaric acid, ferulic acid, vanillic acid, 4-hydroxybenzoic acid (4-HBA), and 3,4-dihydroxybenzoic acid (3,4-DHBA). Pseudomonas putida JCM 13063 also grew in the presence of 4-HBA, 3,4-DHBA, and vanillic acid. Another strain, Ralstonia eutropha H16, synthesized PHA from 4-HBA, 2,5-DHBA, and 3,4-DHBA. On the basis of the data obtained from these experiments, we suggest that the conversion of lignin derivatives into intermediates such as 4-HBA, 2,5-DHBA, 3,4-DHBA, and vanillic acid represents the major bottleneck in the synthesis of PHA from lignin derivatives.