Lignin, the main component of the plant’s cell wall and the most abundant aromatic macromolecule, is known for its resistance to degradation, therefore its valorization is a crucial stride towards ...fostering cleaner consumption and production. The applications of microbial ligninolytic enzymes for achieving efficient lignin biotransformation have gained much attention recently. This review summarized the structural characteristics of lignin which aids recalcitrance to its degradation, and the recent progress in harnessing ligninolytic enzymes for efficient lignin bio-depolymerization. This review discusses the evolution and engineering of ligninolytic enzymes with a particular focus on the role of artificial intelligence in revolutionizing enzyme engineering. Synthesis of lipids, aromatics, ring-opening compounds, and polyhydroxyalkanoate through lignin biotransformation is discussed to highlight its versatility as a source of value-added chemicals. The current state of knowledge, possible gaps, and future directions are also presented. The integration of structural understandings, enzymatic mechanisms, and downstream applications offers a holistic overview, making it a helpful resource for researchers in lignin valorization.
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•Lignin is an abundant source of aromatic compounds for high-value utilization.•Ligninolytic enzymes play a pivotal role in lignin biotransformation processes.•Artificial intelligence can be the game changer in lignin biotransformation.•Lipids, aromatics, ring-opening compounds, and polyhydroxyalkanoate are key products.•Lignin transformation into a valuable resource is vital for a sustainable bio-economy.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
Fungal pretreatment on lignocellulosic biomass has the advantages of being eco-friendly, having low operating cost, and producing no inhibitor. In this study, six white-rot fungi (
Trametes ...versicolor
,
Pleurotus ostreatus
,
Phanerochaete chrysosporium
,
Coriolopsis gallica
,
Pleurotus sajor-caju
,
Lentinula edodes
) were applied to corn stover pretreatment. Biomass degradation, production of enzymes, reducing sugar via hydrolysis, and ethanol yield via yeast fermentation were quantified during 30 days cultivation, and samples were taken every 5 days. Among six fungi, the highest lignin degradation was 38.29% at 30 days for
P. sajor-caju
pretreatment, the highest sugar yield was 71.24%, and the highest ethanol yield was 0.124 g g
−1
corn stover under
P. sajor-caju
pretreatment for 25 days. The highest activities of laccase and manganese peroxidase were 29.22 and 10.22 U g
−1
dry biomass, respectively, under
T. versicolor
pretreatment at 25 days. The highest levels of enzyme, sugar, and ethanol production are comparable or higher than what has been reported in previous literature.
P. sajor-caju
is one of the most widely worldwide cultivated mushrooms. The findings in this study show the potential to incorporate
P. sajor-caju
mushroom cultivation into corn stover pretreatment to enhance the production of a suite of products such as enzymes, sugars, and ethanol.
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CEKLJ, DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The Front Cover shows the formation of low‐molecular‐weight compounds by the oxidative depolymerization of lignin by the laccase‐Lig multienzymatic multistep system. More information can be found in ...the Research Article by E. Vignali, M. Gigli, et al.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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•Lignin is the most abundant heteropolymer for conversion into aromatic compounds.•Lignin modifying and degrading enzymes deconstruct the rigid lignin structure.•Slow rate of ...enzymatic reaction is a major challenge towards lignin valorization.•Lignin valorization is must for economically feasible biorefinery of biomass.
Lignin is the 3rd most abundant biopolymer surpassed by cellulose and hemicellulose and is the most abundant aromatics resource available on earth for utilization by mankind. It was considered undesirable historically which was usually burned as inefficient fuel. Lignin’s 3D recalcitrant nature caused hinderance to feasible biorefinery of holocellulosic fraction of biomass; however, with the rise of lignin biorefinery the concept has changed completely. Now modern biorefinery of biomass insists on making complete value of all the streams including lignin by valorising into variety of phenolics, biopolymers and other high value-added chemicals. Biological depolymerisation of lignin via enzymes is environmentally benign and preferred approach by virtue of low chemical requirement and disposal and energy demand; however, economic challenges are ahead. Robust enzymes are available in nature which can either modify or depolymerise lignin to add further value. Lignin modifying as well as lignin degrading auxiliary enzymes are instrumental and pave the way to a green process for lignin valorisation. This review article is focussed on various lignin degrading as well as lignin modifying enzymes produced by microorganisms especially fungi for degradation or modification of lignin, and its mechanisms, along with the strength and challenges for sustainable bio-based economy development.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
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•Peroxidases were produced with low-cost residue via solid fermentation.•Biodegradation process was improved and the byproducts structures were proposed.•Methyl green in-vitro ...degradation products showed lower toxicity than original dye.•Congo red in-vitro degradation products showed higher toxicity than original dye.•Successful use of crude extract could mitigate the high costs of purification steps.
This work aimed to provide information that contributes to establishing environmental-friendly methods for synthetic dyes’ degradation. The potential decolorization capacity of the crude enzymatic extract produced by Phanerochaete chrysosporium CDBB 686 using corncob as a substrate was evaluated on seven different dyes. Critical variables affecting the in-vitro decolorization process were further evaluated and results were compared with an in-vivo decolorization system. Decolorization with enzymatic extracts presented advantages over the in-vivo system (higher or similar decolorization within a shorter period). Under improved in-vitro process conditions, the dyes with higher decolorization were: Congo red (41.84 %), Poly R-478 (56.86 %), Methyl green (69.79 %). Attempts were made to confirm the transformation of the dyes after the in-vitro process as well as to establish a molecular basis for interpreting changes in toxicity along with the degradation process. In-vitro degradation products of Methyl green presented a toxicity reduction compared with the original dye; however, increased toxicity was found for Congo red degradation products when compared with the original dyes. Thus, for future applications, it is crucial to evaluate the mechanisms of biodegradation of each target synthetic dye as well as the toxicity of the products obtained after enzymatic oxidation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
Ligninolytic enzymes from white-rot fungi are widely used in biotechnological processes. However, the application of these enzymes as free enzymes is limited due to their instability and lack of ...reusability. Enzyme stabilization is therefore a major challenge in biocatalytic process research, and immobilization methods are desirable. Using cross-linked enzyme aggregates (CLEAs) such as magnetic CLEAs, porous-CLEAs and combi-CLEAs is a promising technique for overcoming these issues. Cross-linking methods can stabilize and immobilize enzymes by interconnecting enzyme molecules via multiple bonds using cross-linking agents such as glutaraldehyde. The high catalyst density and microporous assembly of CLEAs guarantee high catalyst activity, which, together with their long shelf life, operational stability, and reusability, provide a cost-efficient alternative to matrix-assisted immobilization approaches. Here, we review current progress in ligninolytic enzyme immobilization and provide a comprehensive review of CLEAs. Moreover, we summarize the use of these CLEAs for biocatalysis processes, bioremediation such as dye decolourization, wastewater treatment or pharmaceutically active compound elimination.
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•Comparison CLEA with another immobilization procedure is summarized.•Various ways to prepare cross-linked enzyme aggregates (CLEAs) are discussed.•Immobilization without a carrier and pure enzyme is an advantage of CLEA method.•CLEA technology is applicable to a wide range of enzymes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK, ZRSKP
7.
Lignin‐degrading enzymes Pollegioni, Loredano; Tonin, Fabio; Rosini, Elena
The FEBS journal,
April 2015, Volume:
282, Issue:
7
Journal Article
Peer reviewed
Open access
A main goal of green biotechnology is to reduce our dependence on fossil reserves and to increase the use of renewable materials. For this, lignocellulose, which is composed of cellulose, ...hemicellulose and lignin, represents the most promising feedstock. The latter is a complex aromatic heteropolymer formed by radical polymerization of guaiacyl, syringyl, and p‐hydroxyphenyl units linked by β‐aryl ether linkages, biphenyl bonds and heterocyclic linkages. Accordingly, lignin appears to be a potentially valuable renewable aromatic chemical, thus representing a main pillar in future biorefinery. The resistance of lignin to breakdown is the main bottleneck in this process, although a variety of white‐rot fungi, as well as bacteria, have been reported to degrade lignin by employing different enzymes and catabolic pathways. Here, recent investigations have expanded the range of natural biocatalysts involved in lignin degradation/modification and significant progress related to enzyme engineering and recombinant expression has been made. The present review is focused primarily on recent trends in ligninolytic green biotechnology to suggest the potential (industrial) application of ligninolytic enzymes. Future perspectives could include synergy between natural enzymes from different sources (as well as those obtained by protein engineering) and other pretreatment methods that may be required for optimal results in enzyme‐based, environmentally friendly, technologies.
Lignin represents a potentially valuable of renewable aromatic chemicals. Owing to its complex structure, considerable effort was devoted to understanding the major natural pathways and enzymes involved in lignin degradation. In this review, recent trends in ligninolytic green biotechnology and the progresses related to engineering and recombinant expression of lignin‐degrading enzymes, are presented.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
As the largest renewable aromatic resource, lignin is a promising feedstock for production of value-added products. However, lignin valorization has not been implemented due to the recalcitrant and ...heterogeneity of lignin. Herein, this work provides a systematic overview of bacterial lignin valorization for producing value-added products from the viewpoint of a cascaded conversion route. The combinatorial depolymerization strategy facilitates the yield of a lignin-derived aromatic stream suitable for the bacterial conversion. Bacterial active transports are curial to improve the uptake of lignin-derived aromatics. Intracellular metabolic pathways of bacteria assimilate heterogenous lignin-derived aromatics through “biological funnel” into central aromatic intermediates. These intermediates can be effectively metabolized in bacteria through aromatic ring cleavage pathways to enable the biosynthesis of various value-added products. The techno-economic analysis highlights that bacterial conversion improves the feasibility of co-production of value-added products from lignin. Therefore, the bacterial cascaded conversion routes hold great promise for upgrading heterogeneous lignin into value-added products and thus contribute to the profitability of lignin valorization.
Cascaded conversion routes of bacterial lignin valorization facilitate production of value-added products. Display omitted
•Cascaded conversion route paves the way for bacterial lignin valorization.•Combinatorial fractionation improves lignin depolymerization and bioconversion.•Bacterial active transports of aromatics are crucial to lignin bioconversion.•Intracellular metabolic pathways assimilate heterogenous lignin-derived aromatics.•Ligninolytic bacteria can convert lignin to value-added products.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
In order to reveal the effects of Wolfiporia cocos lignocellulolytic enzymes and culture methods on its main enzymes, the main lignocellulolytic enzymes of W. cocos were determined in this study. The ...microscopic observation of the culture characteristics of the wild W. cocos strains was carried out, three pairs of primers were used for PCR amplification to carry out phylogenetic identification, and the dominant strain YX1 was screened by qualitative culture and finally the activities of cellulase, hemicellulase and ligninolytic enzymes under different conditions were determined by microplate reader. The results were as follows:（1）W. cocos had mycelium, fruiting body and sclerotium three morphological characteristics.（2）PCR obtained rDNA-ITS sequence of 1 652 bp, ribosomal large subunit sequence of 660 bp and translation elongation factor sequence of 545 bp, and submitted to NCBI，accession numbers were ON129554, ON129553, and ON155840, respectively.（3）The highest secretion of exo-β-glucanase(CBH), endo-β-gluca
Lignin represents an untapped resource in lignocellulosic biomass, primarily due to its recalcitrance to depolymerization and its intrinsic heterogeneity. In Nature, microorganisms have evolved ...mechanisms to both depolymerize lignin using extracellular oxidative enzymes and to uptake the aromatic species generated during depolymerization for carbon and energy sources. The ability of microbes to conduct both of these processes simultaneously could enable a Consolidated Bioprocessing concept to be applied to lignin, similar to what is done today with polysaccharide conversion to ethanol viaethanologenic, cellulolytic microbes. To that end, here we examine the ability of 14 bacteria to secrete ligninolytic enzymes, depolymerize lignin, uptake aromatic and other compounds present in a biomass-derived, lignin-enriched stream, and, under nitrogen-limiting conditions, accumulate intracellular carbon storage compounds that can be used as fuel, chemical, or material precursors. In shake flask conditions using a substrate produced during alkaline pretreatment, we demonstrate that up to nearly 30% of the initial lignin can be depolymerized and catabolized by a subset of bacteria. In particular, Amycolatopsissp., two Pseudomonas putidastrains, AcinetobacterADP1, and Rhodococcus jostiiare able to depolymerize high molecular weight lignin species and catabolize a significant portion of the low molecular weight aromatics, thus representing good starting hosts for metabolic engineering. This study also provides a comprehensive set of experimental tools to simultaneously study lignin depolymerization and aromatic catabolism in bacteria, and provides a foundation towards the concept of Lignin Consolidated Bioprocessing, which may eventually be an important route for biological lignin valorization.
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