Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands.
Department of Microbiology, University of Helsinki, Viikinkaari 9, Helsinki, Finland.
Biotechnol Adv. 2019 Nov 15;37(7):107396. doi: 10.1016/j.biotechadv.2019.05.002. Epub 2019 May 7.
Aromatic compounds derived from lignin are of great interest for renewable biotechnical applications. They can serve in many industries e.g. as biochemical building blocks for bioplastics or biofuels, or as antioxidants, flavor agents or food preservatives. In nature, lignin is degraded by microorganisms, which results in the release of homocyclic aromatic compounds. Homocyclic aromatic compounds can also be linked to polysaccharides, tannins and even found freely in plant biomass. As these compounds are often toxic to microbes already at low concentrations, they need to be degraded or converted to less toxic forms. Prior to ring cleavage, the plant- and lignin-derived aromatic compounds are converted to seven central ring-fission intermediates, i.e. catechol, protocatechuic acid, hydroxyquinol, hydroquinone, gentisic acid, gallic acid and pyrogallol through complex aromatic metabolic pathways and used as energy source in the tricarboxylic acid cycle. Over the decades, bacterial aromatic metabolism has been described in great detail. However, the studies on fungal aromatic pathways are scattered over different pathways and species, complicating a comprehensive view of fungal aromatic metabolism. In this review, we depicted the similarities and differences of the reported aromatic metabolic pathways in fungi and bacteria. Although both microorganisms share the main conversion routes, many alternative pathways are observed in fungi. Understanding the microbial aromatic metabolic pathways could lead to metabolic engineering for strain improvement and promote valorization of lignin and related aromatic compounds.
来源于木质素的芳香族化合物在可再生生物技术应用中具有很大的兴趣。它们可以用于许多行业，例如作为生物塑料或生物燃料的生化构建块，或作为抗氧化剂、香料或食品防腐剂。在自然界中，木质素被微生物降解，导致同环芳香族化合物的释放。同环芳香族化合物也可以与多糖、单宁结合，甚至在植物生物质中自由存在。由于这些化合物在低浓度时对微生物通常就具有毒性，因此需要对其进行降解或转化为毒性较小的形式。在进行环裂解之前，植物和木质素衍生的芳香族化合物通过复杂的芳香族代谢途径转化为七个中心环裂中间体，即儿茶酚、原儿茶酸、羟基喹啉、对苯二酚、龙胆酸、没食子酸和焦儿茶酚，然后作为三羧酸循环中的能量源被利用。几十年来，细菌芳香族代谢已被详细描述。然而，真菌芳香途径的研究分散在不同的途径和物种中，这使得真菌芳香代谢的全貌变得复杂。在这篇综述中，我们描述了真菌和细菌中报道的芳香代谢途径的相似性和差异。尽管这两种微生物都共享主要的转化途径，但在真菌中观察到许多替代途径。了解微生物的芳香代谢途径可能导致对菌株的代谢工程改良，并促进木质素和相关芳香族化合物的增值。
