Emerging Strategies for Modifying Lignin Chemistry to Enhance Biological Lignin Valorization

Abstract

Biological lignin valorization represents a promising approach contributing to sustainable and economic biorefineries. The low level of valuable lignin-derived products remains a major challenge hindering the implementation of microbial lignin conversion. Lignin's properties play a significant role in determining the efficiency of lignin bioconversion. To date, despite significant progress in the development of biomass pretreatment, lignin fractionation, and fermentation over the last few decades, little efforts have gone into identifying the ideal lignin substrates for an efficient microbial metabolism. In this Minireview, emerging and state-of-the-art strategies for biomass pretreatment and lignin fractionation are summarized to elaborate their roles in modifying lignin structure for bioconversion. Fermentation strategies aimed at enhancing lignin depolymerization for microbial utilization are systematically reviewed as well. With an improved understanding of the ideal lignin structure elucidated by comprehensive metabolic pathways and/or big data analysis, modifying lignin chemistry could be more directional and effective. Ultimately, together with the progress of fermentation process optimization, biological lignin valorization will become more competitive in biorefineries.

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

“…The lignin used in this study is alkali lignin, which seems to have low bioavailability due to the repolymerization reaction during lignin preparation (Toledano et al, 2014). Plentiful strategies have been established to enhance lignin bioavailability for microbial utilization, such as improving lignin output with combinatorial pretreatment of biomass (Liu et al, 2018), increasing water solubility for lignin by alkali sterilization (Zhao et al, 2021), improving lignin distribution uniformity with cosolvent enhanced lignocellulosic fractionation pretreatment (Meng et al, 2018; Zhao et al, 2020). In addition, tailoring lignin biosynthesis in plants is a direct approach to obtain suitable lignin substrate for biological conversion.…”

Phosphoric acid-modified commercial kieselguhr supported palladium nanoparticles as efficient catalysts for low-temperature hydrodeoxygenation of lignin derivatives in water

“…However, because of the high oxygen content in lignin or lignin pyrolysis derivatives, the hydrodeoxygenation (HDO) process to remove partial oxygen from these feedstocks is regarded as an effective route to produce high value-added chemicals and energetic biofuels. [7][8][9][10][11][12] On the other hand, >10 wt% of water is co-pro-duced during the production of lignin derivatives by direct pyrolysis of lignin or lignocellulosic biomass and a certain amount of generated lignin derivatives is miscible with water. [13][14][15][16][17][18] Therefore, direct HDO of lignin derivatives in water to avoid the energy-consuming separation process is highly desired for the maximum utilization of renewable carbon resources.…”

Synthesis and Antibacterial Properties of Oligomeric Dehydrogenation Polymer from Lignin Precursors

“…In the process of synthesising DHP, the reaction conditions can be artificially controlled to adjust the type of DHP produced [ 22 , 23 ]. Therefore, DHP has a low degree of polymerisation, simple structure, and connectivity, and more functional groups can be obtained, which can achieve higher biological activity than natural lignin [ 24 , 25 , 26 ].…”