Lignin Degradation Processes and the Purification of Valuable Products

Abstract

Lignin is a heterogeneous, phenolic and polydisperse biopolymer which resists degradation due to its aromatic and highly branched structure. Lignin is the most abundant renewable source of aromatic molecules on earth. The valorization of lignin could therefore provide a sustainable alternative to petroleum refineries for the production of valuable aromatic compounds. Even so, paper mills and lignocellulose feedstock biorefineries treat lignin largely as a waste product. In paper mills, 98% of technical lignin is incinerated for internal energy recovery while only 2% is used commercially (e.g. for the production of aromatics such as vanillin). The reasons for the underutilization of lignin include its recalcitrance to degradation and the challenge of separating mixtures of numerous degradation products. The successful valorization of lignin in the future thus depends on a broad understanding of biological and technical degradation processes, and the implementation of efficient product purification strategies. This article describes enzymatic, photocatalytic and thermochemical lignin degradation processes and considers purification methods for valuable lignin-derived degradation products. We focus on the potential of membrane-based separation technology, including data from our own recent research.

Deconstruction of Lignin: From Enzymes to Microorganisms

“…Lignin is the main plant cell wall component responsible for recalcitrance [ 6 ]. Thus, pretreatment is an essential step for removing lignin in the process of lignocellulosic biomass conversion into biofuels [ 7 , 8 ]. The high carbon/oxygen ratio and the natural abundance of lignin make it a promising feedstock material for biological conversion into value-added products [ 9 ].…”

Bacterial (9A2H) enhancement alters the nematode community structure and decomposition pathway of amended nutrient-limited soil

“…The nematode community changed which larger-body nematodes of omnivores and carnivores were abundant. No bacterial addition to soil might increase fungal growth; this is possible because paddy litter contains a large amount of lignin, suitable for fungal degradation but not bacterial degradation (Janusz et al 2017, Schoenherr et al 2018. After 41 days, as recorded by the data, fungal decomposition of paddy litter might have provided smaller molecules for use by the natural opportunistic bacteria (De Vries and Caruso 2016).…”

Keramische Membrantechnologie für die Verfügbarmachung biogener Stoffströme

“…Diese Biomasse ist eine natürliche und reichlich vorhandene erneuerbare Ressource, die beispielsweise als geeigneter Kohlenstofflieferant für die Synthese funktioneller Kohlenstoffmaterialien angesehen werden kann [4,7]. Die lignozellulosehaltige Biomasse ist der wichtigste strukturelle Bestandteil von Pflanzen und setzt sich zusammen aus Zellulose (40-60 %), Hemicellulose (10-40 %), Lignin (15-30 %) sowie geringen Mengen an Extrakten, Proteinen und anorganischen Verbindungen [7,8] (Abb. 1).…”

“…70 Millionen Tonnen anfällt [7]. Der größte Teil dieses ,,Abfallproduktes'' wird zur Dampf-, Wärme-und Stromerzeugung verbrannt (etwa 98 % des gesamten anfallenden Lignins), während ein sehr kleiner Teil zur Herstellung von Produkten verwendet wird [8].…”