Biotransformation of lignin: Mechanisms, applications and future work

Abstract

As one of the most abundant polymers in biosphere, lignin has attracted extensive attention as a kind of promising feedstock for biofuel and bio-based products. However, the utilization of lignin presents various challenges in that its complex composition and structure and high resistance to degradation. Lignin conversion through biological platform harnesses the catalytic power of microorganisms to decompose complex lignin molecules and obtain value-added products through biosynthesis.Given the heterogeneity of lignin, various microbial metabolic pathways are involved in lignin bioconversion processes, which has been characterized in extensive research work. With different types of lignin substrates (e.g., model compounds, technical lignin, and lignocellulosic biomass), several bacterial and fungal species have been proved to own lignin-degrading abilities and accumulate microbial products (e.g., lipid

Emerging Strategies for Modifying Lignin Chemistry to Enhance Biological Lignin Valorization

“…Furthermore, biomass pretreatment could depolymerize lignins to some derivatives that are easy to be converted into these known reactive monomers, but these molecules have not been exactly identified. The target lignin structure desired to produce through pretreatment and further fractionation is still not that clear, although it is critical for guiding the lignin modification for bioconversion . There are two general ways to identify the ideal lignin structure: 1) metabolic pathways of microorganisms should be further studied to clarify the lignin metabolism, although this systematic approach is complicated and time consuming.…”

“…The target lignin structure desired to produce through pretreatment and further fractionation is still not that clear, although it is critical for guiding the lignin modification for bioconversion. [46] There are two general ways to identify the ideal lignin structure: 1) metabolic pathways of microorganisms should be further studied to clarify the lignin metabolism, although this systematic approach is complicated and time consuming. 2) Another relatively simple way is portraying the ideal lignin substrates through big data analysis.…”

Lignin bioconversion into valuable products: fractionation, depolymerization, aromatic compound conversion, and bioproduct formation

“…Some of the genes and enzymes regulating the pathways such as β-ketoadipate were bountiful in several other microbes including those in the genera Pseudomonas, Rhodococci, Acinetobacter, Amycolatopsis, Sphingomonas, Streptomyces, Burkholderia, Citrobacteria, Bacillus, Pandoraea, Thraustochytrium, and Corynebacterium, which all have been shown as promising candidates for biological lignin valorization [75,77,108,[194][195][196]. For systems and synthetic biology approaches to create more efficient pathways to boost lignin depolymerization and conversion into valuable products, the readers can refer to Li and Zheng [197], Liu et al [198] and Becker and Wittmann [5] for more information.…”

Newly identified genes contribute to vanillin tolerance in Saccharomyces cerevisiae

“…Moreover, vanillin is one of the most widely used flavouring agents in the food industry. Efforts have been made to produce vanillin by microorganisms from other components of lignin, such as ferulic acid (Li and Zheng 2020, Liang et al ., 2020), and some efforts have been directed towards de novo synthesis of vanillin from glucose (Hansen et al ., 2009). Exploring the cellular mechanisms related to vanillin tolerance is important for constructing robust cellular factories that either utilize the lignocellulosic materials or that produce vanillin (Wang et al ., 2017, Pattrick et al 2019).…”