Issue 5, 2016

Synergistic enzymatic and microbial lignin conversion

Abstract

The utilization of lignin for fungible fuels and chemicals represents one of the most imminent challenges in modern biorefineries. However, bioconversion of lignin is highly challenging due to its recalcitrant nature as a phenolic heteropolymer. This study addressed the challenges by revealing the chemical and biological mechanisms for synergistic lignin degradation by a bacterial and enzymatic system, which significantly improved lignin consumption, cell growth and lipid yield. The Rhodococcus opacus cell growth increased exponentially in response to the level of laccase treatment, indicating the synergy between laccase and bacterial cells in lignin degradation. Other treatments like iron and hydrogen peroxide showed limited impact on cell growth. Chemical analysis of lignin under various treatments further confirmed the synergy between laccase and cells at the chemical level. 31P nuclear magnetic resonance (NMR) suggested that laccase, R. opacus cell and Fenton reaction reagents promoted the degradation of different types of lignin functional groups, elucidating the chemical basis for the synergistic effects. 31P NMR further revealed that laccase treatment had the most significant impact for degrading the abundant chemical groups. The results were further confirmed by the molecular weight analysis and lignin quantification by the Prussian blue assay. The cell–laccase fermentation led to a 17-fold increase of lipid production. Overall, the study indicated that laccase and R. opacus can synergize to degrade lignin efficiently, likely through rapid utilization of monomers generated by laccase to promote the reaction toward depolymerization. The study provided a potential path for more efficient lignin conversion and development of consolidated lignin conversion.

Graphical abstract: Synergistic enzymatic and microbial lignin conversion

Supplementary files

Article information

Article type
Paper
Submitted
20 Aug 2015
Accepted
02 Oct 2015
First published
02 Oct 2015

Green Chem., 2016,18, 1306-1312

Author version available

Synergistic enzymatic and microbial lignin conversion

C. Zhao, S. Xie, Y. Pu, R. Zhang, F. Huang, A. J. Ragauskas and J. S. Yuan, Green Chem., 2016, 18, 1306 DOI: 10.1039/C5GC01955A

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