Mattoo Aroosa Jan, Nonzom Skarma
Department of Botany, University of Jammu, Jammu, India.
Front Bioeng Biotechnol. 2022 Jul 19;10:895414. doi: 10.3389/fbioe.2022.895414. eCollection 2022.
Lignin, one of the essential components of lignocellulosic biomass, comprises an abundant renewable aromatic resource on the planet earth. Although 15%--40% of lignocellulose pertains to lignin, its annual valorization rate is less than 2% which raises the concern to harness and/or develop effective technologies for its valorization. The basic hindrance lies in the structural heterogeneity, complexity, and stability of lignin that collectively makes it difficult to depolymerize and yield common products. Recently, microbial delignification, an eco-friendly and cheaper technique, has attracted the attention due to the diverse metabolisms of microbes that can channelize multiple lignin-based products into specific target compounds. Also, endophytes, a fascinating group of microbes residing asymptomatically within the plant tissues, exhibit marvellous lignin deconstruction potential. Apart from novel sources for potent and stable ligninases, endophytes share immense ability of depolymerizing lignin into desired valuable products. Despite their efficacy, ligninolytic studies on endophytes are meagre with incomplete understanding of the pathways involved at the molecular level. In the recent years, improvement of thermochemical methods has received much attention, however, we lagged in exploring the novel microbial groups for their delignification efficiency and optimization of this ability. This review summarizes the currently available knowledge about endophytic delignification potential with special emphasis on underlying mechanism of biological funnelling for the production of valuable products. It also highlights the recent advancements in developing the most intriguing methods to depolymerize lignin. Comparative account of thermochemical and biological techniques is accentuated with special emphasis on biological/microbial degradation. Exploring potent biological agents for delignification and focussing on the basic challenges in enhancing lignin valorization and overcoming them could make this renewable resource a promising tool to accomplish Sustainable Development Goals (SDG's) which are supposed to be achieved by 2030.
木质素是木质纤维素生物质的重要组成部分之一，是地球上丰富的可再生芳香资源。尽管木质纤维素的15% - 40%是木质素，但其年增值率不到2%，这引发了人们对开发有效增值技术的关注。基本障碍在于木质素的结构异质性、复杂性和稳定性，这些因素共同导致其难以解聚并生成常见产品。近年来，微生物脱木质素作为一种环保且成本较低的技术，由于微生物的多样代谢能够将多种基于木质素的产物转化为特定目标化合物而受到关注。此外，内生菌是一类奇妙的微生物群体，无症状地生活在植物组织内，具有惊人的木质素解构潜力。除了是强效和稳定的木质素酶的新来源外，内生菌还具有将木质素解聚为所需有价值产品的巨大能力。尽管它们具有功效，但关于内生菌的木质素分解研究仍然很少，对分子水平上所涉及的途径了解不完整。近年来，热化学方法的改进受到了广泛关注，然而我们在探索新型微生物群体的脱木质素效率及其能力优化方面仍滞后。本综述总结了目前关于内生菌脱木质素潜力的现有知识，特别强调了生物转化生产有价值产品的潜在机制。它还突出了开发最具吸引力的木质素解聚方法的最新进展。着重比较了热化学和生物技术，特别强调生物/微生物降解。探索用于脱木质素的有效生物制剂，并关注提高木质素增值的基本挑战并克服它们，可能会使这种可再生资源成为实现2030年可持续发展目标（SDG）的有前途的工具。
