Developing Rhodococcus opacus and Sphingobium sp. coculture systems for valorization of lignin‐derived dimers

Abstract

Bioconversion is being regarded as a promising way for lignin valorization because it enables funneling diverse lignin components into single compounds, overcoming the heterogeneity of lignin. Although numerous lignin‐derived aromatic monomers have been funneled to target compounds in previous studies, the bioconversion of low‐molecular‐weight lignin (LMW‐lignin) fragments, for example, lignin‐derived dimers, has been rarely systematically studied, impeding further conversion of lignin. In this study, coculture systems were designed and developed to funnel multiple lignin‐derived dimers to cis, cis‐muconate and gallate by combining lignin‐derived dimers cleavage bacterium Sphingobium sp. and monomers conversion bacterium Rhodococcus opacus. With the developed coculture systems, β‐O‐4 type dimer guaiacylglycerol‐β‐guaiacyl ether, 4‐O‐5 type dimer 4,4′‐dihydroxydiphenyl ether, β‐5 type dimer balanophonin, β‐β type dimer pinoresinol, β‐1 type dimer 1,2‐bis(4‐hydroxy‐3‐methoxyphehyl)‐1,3‐propanediol and 5‐5 type dimer 5,5′‐dehydrodivanillate were converted to cis, cis‐muconate. Additionally, the developed coculture systems also showed potential in conversion of lignin‐derived dimers to gallate. The application of alkali lignin for cis, cis‐muconate production further demonstrated the effectiveness of the designed coculture systems. Overall, the developed coculture systems are beneficial to lignin biological valorization, and also provide references for the valorization of other bio‐resources.

Biotransformation of lignin into 4-vinylphenol derivatives toward lignin valorization

“…[34][35][36] These ligninolytic enzymes boost the depolymerization of the highmolecular-weight lignin polymers into aromatic dimers and monomers. 37 For example, laccase purified from Bacillus sp. PCH94 treated kraft lignin and yielded more FA, acetovanillone and three dimers.…”

Perspectives and advances in consolidated bioprocessing strategies for lignin valorization

“…It must be stated here that microbial consortia generally have higher metabolic flexibility than single cultures, and the introduction of multiple genes into a chassis cell is challenging due to the heavy metabolic burden and unclear pathways. 171 The development of a microbial consortium is a promising approach for lignin valorization that may overcome the difficulties faced by a single recombinant strain in lignin CBP. In conclusion, microorganisms or microbial consortiums that can simultaneously perform multiple complex lignin catabolism functions are of great significance for establishing a lignin CBP platform with greater synthetic potential for lignin value-added products.…”

“…173 This approach enables the manipulation of genetic content and regulatory processes. Cai et al 171 designed a co-culture system of R. opacus PD630 and Sphingobium sp . SYK-6 by modifying the lignin catabolic pathway and demonstrated the effectiveness of the synthetic microbial consortium in promoting the bioconversion of lignin components.…”

Top-down and bottom-up microbiome engineering approaches to enable biomanufacturing from waste biomass

“…Synthetic microbial consortia have been so far used for syngas waste and lignocellulosic biomass conversion (Shahab et al., 2020a ; Diender et al., 2021 ; Cai et al., 2022 ). By leveraging the concept of metabolic division of labor (DOL), researchers can design a consortium to achieve specific waste valorization goals.…”

“…For example, simultaneous lignin depolymerization and upgrading is challenging to achieve in a monoculture system compared to microbial consortia, due to its complex structure and toxic lignin-derived compounds (Shrestha et al., 2024 ). A co-culture system consisting of Sphingobium and Rhodococcus opacus was able to effectively break down lignin via DOL, with each strain handling separate steps during conversion of lignin-derived dimers and aromatic monomers to cis, cis ‐muconate, and gallate (Cai et al., 2022 ). Another study successfully designed a three-member consortium of T. reesei, Lactiplantibacillus pentosus , and Clostridium tyrobutyricum for efficient conversion of lignocellulose-derived components through DOL.…”