Enhanced degradation of lignin by the strain fusion of Pseudomonas putida and Gordonia sp

Abstract

The protoplast fusion technique was applied to construct a more efficient engineering microbial strain to degrade lignin by fusing two strains, Pseudomonas putida and Gordonia sp. At an initial lignin concentration of 900 mg/L, COD, BOD, TOC removal efficiencies increased from 69–76%, 69–72%, and 70–72% by the parent stains to 83%, 83%, and 83% of the fused strain, respectively. IR and HPLC analyses of the treated solution suggested that the fused strains were more capable of breaking the Cα–Cβ bonds of the benzene ring in lignin compared to its parent strains, yielding syringyls as the main product. GC–MS analysis was used to identify the release of three-types of lower molecular intermediates: ring-opening, monomer, and dipolymer products. The phenolic hydroxyl group in lignin was oxidized to carbonyls, followed by further degradation to acids and esters. The carboxyl group on the ether linkage that maintains the macromolecular structure of lignin was oxidized to acyls, which further led to depolymerization and the opening of benzene ring.