A Review on the Utilization of Lignin as a Fermentation Substrate to Produce Lignin-Modifying Enzymes and Other Value-Added Products

Abstract

The lignocellulosic biomass is comprised of three major components: cellulose, hemicellulose, and lignin. Among these three, cellulose and hemicellulose were already used for the generation of simple sugars and subsequent value-added products. However, lignin is the least applied material in this regard because of its complex and highly variable nature. Regardless, lignin is the most abundant material, and it can be used to produce value-added products such as lignin-modifying enzymes (LMEs), polyhydroxyalkanoates (PHAs), microbial lipids, vanillin, muconic acid, and many others. This review explores the potential of lignin as the microbial substrate to produce such products. A special focus was given to the different types of lignin and how each one can be used in different microbial and biochemical pathways to produce intermediate products, which can then be used as the value-added products or base to make other products. This review paper will summarize the effectiveness of lignin as a microbial substrate to produce value-added products through microbial fermentations. First, basic structures of lignin along with its types and chemistry are discussed. The subsequent sections highlight LMEs and how such enzymes can enhance the value of lignin by microbial degradation. A major focus was also given to the value-added products that can be produced from lignin.

Recent Biotechnology Advances in Bio-Conversion of Lignin to Lipids by Bacterial Cultures

“…Ligninolytic enzymes, which are crucial for lignin valorization, are mainly divided into two groups, i.e., lignin modifying enzymes (LMEs) and lignin-degrading auxiliary enzymes (LDAs) ( Iram et al, 2021 ). LMEs, including laccase and peroxidase (e.g., lignin peroxidase, manganese peroxidase, multifunctional peroxidases, etc.…”

“…As attractive feedstocks for biofuel production, lipids can be synthesized from lignin-based aromatic building blocks by oleaginous microorganisms with nearly 20% of lipids accumulation out of their dry cell weight (DCW) ( Reshmy et al, 2022 ). Prominent oleaginous bacteria can exhibit excellent lipid accumulation capacities, such as Acinetobacter calcoaceticus (lipid accumulation up to 27%–38% of their DCW), Rhodococcus opacus (25%), and Bacillus alcalophilus (18%–24%) ( Iram et al, 2021 ). Biocatalytic processes that integrate upstream depolymerization and bacterial aromatic metabolic pathways (bio-funneling process) can overcome the lignin inherent heterogeneity ( Linger et al, 2014 ).…”

Mystifications and misconceptions of lignin: revisiting understandings

“…A constantly reproduced but highly questionable statement is the lignin's attribution as the "second most abundant organic/biopolymer (and similar) in the world". [131][132][133][134][135] Most scientific references indicate that the total lignin in the biosphere is estimated at 3 × 10 11 tonnes with a growth rate of 2 × 10 10 tonnes per year. [136][137][138][139][140] Strangely enough, no update could be found since 1987.…”

Pineapple Agro-Industrial Biomass to Produce Biomedical Applications in a Circular Economy Context in Costa Rica

“…There arephysicochemical technology and biological techniques that can be employed during lignin depolymerization: The first is achieved through the use of high temperatures and chemical additives, catalysts, and other compounds, which are commonly used in industrial areas. While the second technique, biological depolymerization, is a slower process, it is more environmentally friendly; this technique uses microorganisms such as bacteria and fungi to degrade lignin due to lignin-modifying enzymes that act by oxidative means, which can be classified according to their specific mechanism-of-action and according to the organism from which they originate [46].…”