Microbial Upgrading of Lignin Depolymerization: Enhancing Efficiency with Lignin-First Catalysis.

Abstract

Chemical lignin depolymerization typically yields a heterogeneous mixture of breakdown products. This study constructed a hybrid conversion scheme pairing reductive catalytic fractionation (RCF) of poplar biomass using a Pd/C catalyst with subsequent cultivation of Rhodococcus opacus PD630 on the resulting lignin breakdown products (LBPs). Compared with base-catalyzed depolymerization performed without Pd/C or molecular hydrogen, RCF-derived LBPs supported greater cell biomass accumulation per gram of feedstock. Residual cellulose after RCF exhibited enzymatic digestibility exceeding 40% saccharification yield. Techno-economic and life cycle analyses, modeled within a cellulosic bioethanol facility, showed a reduction in the minimum ethanol selling price from $4.07 to $3.94 per gallon, with global warming potentials between 29 and 30.5 CO2eq/MJ. The findings support the feasibility of an industrial biorefinery integrating lignin-first catalytic deconstruction with microbial valorization.

Mechanism

RCF using Pd/C and molecular hydrogen modifies the composition of lignin breakdown products, improving their assimilability by R. opacus PD630 and simultaneously enhancing enzymatic saccharification of residual cellulose in the treated biomass.