Identification of novel glycosyl hydrolases with cellulolytic activity against crystalline cellulose from metagenomic libraries constructed from bacterial enrichment cultures

Recent advances in metagenomic analysis of different ecological niches for enhanced biodegradation of recalcitrant lignocellulosic biomass

Lignocellulose wastes stemming from agricultural residues can offer an excellent opportunity as alternative energy solutions in addition to fossil fuels. Besides, the unrestrained burning of agricultural residues can lead to the destruction of the soil microflora and associated soil sterilization. However, the difficulties associated with the biodegradation of lignocellulose biomasses remain as a formidable challenge for their sustainable management. In this respect, metagenomics can be used as an effective option to resolve such dilemma because of its potential as the next generation sequencing technology and bioinformatics tools to harness novel microbial consortia from diverse environments (e.g., soil, alpine forests, and hypersaline/acidic/hot sulfur springs). In light of the challenges associated with the bulk-scale biodegradation of lignocellulose-rich agricultural residues, this review is organized to help delineate the fundamental aspects of metagenomics towards the assessment of the microbial consortia and novel molecules (such as biocatalysts) which are otherwise unidentifiable by conventional laboratory culturing techniques. The discussion is extended further to highlight the recent advancements (e.g., from 2011 to 2022) in metagenomic approaches for the isolation and purification of lignocellulolytic microbes from different ecosystems along with the technical challenges and prospects associated with their wide implementation and scale-up. This review should thus be one of the first comprehensive reports on the metagenomics-based analysis of different environmental samples for the isolation and purification of lignocellulose degrading enzymes.

Prospects of soil microbiome application for lignocellulosic biomass degradation: An overview

Sustainable and practically viable biofuels production technology using lignocellulosic biomass is still seeking its way of implementation owing to some major issues involved therein. Unavailability of efficient microbial sources for the degradation of cellulosic biomass is one of the major roadblocks in biomass to biofuels production technology. In this context, utilization of microbiomes to degrade lignocellulaosic biomass is emerging as a rapid and effective approach that can fulfill the requirements of biomass based biofuels production technology. Therefore, the present review is targeted to explore soil metagenomic approach to improve the lignocellulosic biomass degradation processing for the cost-effective and eco-friendly application. Soil microbiomes consist of rich microbial community along with high probability of cellulolytic microbes, and can be identified by culture independent metagenomics method which can be structurally and functionally explored via genomic library. Therefore, in depth analysis and discussion have also been made via structural & functional metagenomics tools along with their contribution to genomic library. Additionally, the present review highlights currently existing bottlenecks along with their feasible solutions. This review will help to understand the basic research as well as industrial concept for the process improvement based on soil microbiome mediated lignocellulosic biomass degradation, and this may likely to implement for the low-cost commercial biofuels production technology.

Metagenomic Approaches as a Tool to Unravel Promising Biocatalysts from Natural Resources: Soil and Water

Natural resources are considered a promising source of microorganisms responsible for producing biocatalysts with great relevance in several industrial areas. However, a significant fraction of the environmental microorganisms remains unknown or unexploited due to the limitations associated with their cultivation in the laboratory through classical techniques. Metagenomics has emerged as an innovative and strategic approach to explore these unculturable microorganisms through the analysis of DNA extracted from environmental samples. In this review, a detailed discussion is presented on the application of metagenomics to unravel the biotechnological potential of natural resources for the discovery of promising biocatalysts. An extensive bibliographic survey was carried out between 2010 and 2021, covering diverse metagenomic studies using soil and/or water samples from different types and locations. The review comprises, for the first time, an overview of the worldwide metagenomic studies performed in soil and water and provides a complete and global vision of the enzyme diversity associated with each specific environment.

Screening of Neutrophil Activating Factors from a Metagenome Library of Sponge-Associated Bacteria

Marine sponge-associated bacteria are known as bio-active compound produce. We have constructed metagenome libraries of the bacteria and developed a metagenomic screening approach. Activity-based screening successfully identified novel genes and novel enzymes; however, the efficiency was only in 1 out of 10⁴ clones. Therefore, in this study, we thought that bioinformatics could help to reduce screening efforts, and combined activity-based screening with database search. Neutrophils play an important role for the immune system to recognize excreted bacterial by-products as chemotactic factors and are recruited to infection sites to kill pathogens via phagocytosis. These excreted by-products are considered critical triggers that engage the immune system to mount a defense against infection, and identifying these factors may guide developments in medicine and diagnostics. We focused on genes encoding amino acid ligase and peptide synthetase and selected from an in-house sponge metagenome database. Cell-free culture medium of each was used in a neutrophil chemiluminescence assay in luminol reaction. The clone showing maximum activity had a genomic sequence expected to produce a molecule like a phospho-N-acetylmuramyl pentapeptide by the metagenome fragment analysis.

Cellulases: From Bioactivity to a Variety of Industrial Applications

Utilization of microbial enzymes has been widely reported for centuries, but the commercial use of enzymes has been recently adopted. Particularly, cellulases have been utilized in various commercial sectors including agriculture, brewing, laundry, pulp and paper and textile industry. Cellulases of microbial origin have shown their potential application in various commercial sectors including textile, pulp and paper, laundry, brewing, agriculture and biofuel. Cellulases have diversified applications in the food industry, food service, food supply and its preservation. Indeed, cellulases can tenderize fruits, clarify the fruit juices, reduce roughage in dough, hydrolyze the roasted coffee, extract tea polyphenols and essential oils from olives and can increase aroma and taste in food items. However, their role in food industries has by and large remained neglected. The use of immobilized cellulases has further expanded their application in fruit and vegetable processing as it potentiates the catalytic power and reduces the cost of process. Technological and scientific developments will further expand their potential usage in the food industry.

Enrichment of waste sewage sludge for enhancing methane production from cellulose

Low ability of waste sewage sludge to degrade cellulose is observed due to its less cellulolytic bacteria content. The enrichment of sewage sludge in the absence or presence of carboxymethylcellulose (CMC) was conducted to improve anaerobic digestion (AD) of cellulose in this study. Compared to initial sewage sludge (IS), enriched sludge without CMC addition (ES) displayed 69.81% higher CH₄ yield and about 1.7-fold greater anaerobic biodegradation of cellulose. In particular, bacterial and archaeal diversities in samples inoculated with ES were significantly altered, with Ruminiclostridium and Methanobacterium as the predominant genera. Enriched sludge with CMC addition (ESC) displayed enhanced methane production at initial cellulose fermentation but showed no distinct difference compared with the control after incubation 24 days. These findings suggest that enrichment of waste sewage sludge without CMC addition is more beneficial for promoting AD of cellulose, providing a novel insight for efficient energy utilization of lignocellulosic wastes.

Characterization of three bacterial glycoside hydrolase family 9 endoglucanases with different modular architectures isolated from a compost metagenome

BACKGROUND

Environmental bacteria express a wide diversity of glycoside hydrolases (GH). Screening and characterization of GH from metagenomic sources provides an insight into biomass degradation strategies of non-cultivated prokaryotes.

METHODS

In the present report, we screened a compost metagenome for lignocellulolytic activities and identified six genes encoding enzymes belonging to family GH9 (GH9a-f). Three of these enzymes (GH9b, GH9d and GH9e) were successfully expressed and characterized.

RESULTS

A phylogenetic analysis of the catalytic domain of pro- and eukaryotic GH9 enzymes suggested the existence of two major subgroups. Bacterial GH9s displayed a wide variety of modular architectures and those harboring an N-terminal Ig-like domain, such as GH9b and GH9d, segregated from the remainder. We purified and characterized GH9 endoglucanases from both subgroups and examined their stabilities, substrate specificities and product profiles. GH9e exhibited an original hydrolysis pattern, liberating an elevated proportion of oligosaccharides longer than cellobiose. All of the enzymes exhibited processive behavior and a synergistic action on crystalline cellulose. Synergy was also evidenced between GH9d and a GH48 enzyme identified from the same metagenome.

CONCLUSIONS

The characterized GH9 enzymes displayed different modular architectures and distinct substrate and product profiles. The presence of a cellulose binding domain was shown to be necessary for binding and digestion of insoluble cellulosic substrates, but not for processivity.

GENERAL SIGNIFICANCE

The identification of six GH9 enzymes from a compost metagenome and the functional variety of three characterized members highlight the importance of this enzyme family in bacterial biomass deconstruction.

Role of metagenomics in prospecting novel endoglucanases, accentuating functional metagenomics approach in second-generation biofuel production: a review

As the fossil fuel reserves are depleting rapidly, there is a need for alternate fuels to meet the day to day mounting energy demands. As fossil fuel started depleting, a quest for alternate forms of fuel was initiated and biofuel is one of its promising outcomes. First-generation biofuels are made from edible sources like vegetable oils, starch, and sugars. Second-generation biofuels (SGB) are derived from lignocellulosic crops and the third-generation involves algae for biofuel production. Technical challenges in the production of SGB are hampering its commercialization. Advanced molecular technologies like metagenomics can help in the discovery of novel lignocellulosic biomass-degrading enzymes for commercialization and industrial production of SGB. This review discusses the metagenomic outcomes to enlighten the importance of unexplored habitats for novel cellulolytic gene mining. It also emphasizes the potential of different metagenomic approaches to explore the uncultivable cellulose-degrading microbiome as well as cellulolytic enzymes associated with them. This review also includes effective pre-treatment technology and consolidated bioprocessing for efficient biofuel production.

Xylanolytic Extremozymes Retrieved From Environmental Metagenomes: Characteristics, Genetic Engineering, and Applications

Xylanolytic enzymes have extensive applications in paper, food, and feed, pharmaceutical, and biofuel industries. These industries demand xylanases that are functional under extreme conditions, such as high temperature, acidic/alkaline pH, and others, which are prevailing in bioprocessing industries. Despite the availability of several xylan-hydrolyzing enzymes from cultured microbes, there is a huge gap between what is available and what industries require. DNA manipulations as well as protein-engineering techniques are also not quite satisfactory in generating xylan-hydrolyzing extremozymes. With a compound annual growth rate of 6.6% of xylan-hydrolyzing enzymes in the global market, there is a need for xylanolytic extremozymes. Therefore, metagenomic approaches have been employed to uncover hidden xylanolytic genes that were earlier inaccessible in culture-dependent approaches. Appreciable success has been achieved in retrieving several unusual xylanolytic enzymes with novel and desirable characteristics from different extreme environments using functional and sequence-based metagenomic approaches. Moreover, the Carbohydrate Active Enzymes database includes approximately 400 GH-10 and GH-11 unclassified xylanases. This review discusses sources, characteristics, and applications of xylanolytic enzymes obtained through metagenomic approaches and their amelioration by genetic engineering techniques.

Cloning of novel bacterial xylanases from lignocellulose-enriched compost metagenomic libraries

Xylanases are in important class of industrial enzymes that are essential for the complete hydrolysis of lignocellulosic biomass into fermentable sugars. In the present study, we report the cloning of novel xylanases with interesting properties from compost metagenomics libraries. Controlled composting of lignocellulosic materials was used to enrich the microbial population in lignocellulolytic organisms. DNA extracted from the compost samples was used to construct metagenomics libraries, which were screened for xylanase activity. In total, 40 clones exhibiting xylanase activity were identified and the thermostability of the discovered xylanases was assayed directly from the library clones. Five genes, including one belonging to the more rare family GH8, were selected for subcloning and the enzymes were expressed in recombinant form in E. coli. Preliminary characterization of the metagenome-derived xylanases revealed interesting properties of the novel enzymes, such as high thermostability and specific activity, and differences in hydrolysis profiles. One enzyme was found to perform better than a standard Trichoderma reesei xylanase in the hydrolysis of lignocellulose at elevated temperatures.

Biochemical Characterization of a Novel Monospecific Endo-β-1,4-Glucanase Belonging to GH Family 5 From a Rhizosphere Metagenomic Library

Cellulases have a broad range of different industrial applications, ranging from food and beverages to pulp and paper and the biofuels area. Here a metagenomics based strategy was used to identify the cellulolytic enzyme CelRH5 from the rhizosphere. CelRH5 is a novel monospecific endo-β-1,4-glucanase belonging to the glycosyl hydrolase family 5 (GH5). Structural based modeling analysis indicated that CelRH5 is related to endo-β-1,4-glucanases derived from thermophilic microorganisms such as Thermotoga maritima, Fervidobacterium nodosum, and Ruminiclostridium thermocellum sharing 30-40% amino acid sequence identity. The molecular weight of the enzyme was determined as 40.5 kDa. Biochemical analyses revealed that the enzyme displayed good activity with soluble forms of cellulose as a substrate such as ostazin brilliant red hydroxyethyl cellulose (OBR-HEC), carboxymethylcellulose (CMC), hydroxyethyl cellulose (HEC), and insoluble azurine cross-linked hydroxyethylcellulose (AZCL-HEC). The enzyme shows highest enzymatic activity at pH 6.5 with high pH tolerance, remaining stable in the pH range 4.5–8.5. Highest activity was observed at 40°C, but CelRH5 is psychrotolerant being active and stable at temperatures below 30°C. The presence of the final products of cellulose hydrolysis (glucose and cellobiose) or metal ions such as Na⁺, K⁺, Li⁺, and Mg²⁺, as well as ethylenediaminetetraacetic acid (EDTA), urea, dithiothreitol (DTT), dimethyl sulfoxide (DMSO), 2-mercaptoethanol (2-ME) or glycerol, did not have a marked effect on CelRH5 activity. However, the enzyme is quite sensitive to the presence of 10 mM ions Zn²⁺, Ni²⁺, Co²⁺, Fe³⁺ and reagents such as 1 M guanidine HCl, 0.1% sodium dodecyl sulfate (SDS) and 20% ethanol. Given that it is psychrotolerant and retains activity in the presence of final cellulose degradation products, metal ions and various reagents, which are common in many technological processes; CelRH5 may be potential suitability for a variety of different biotechnological applications.

Metagenomic analysis of uncultured microorganisms and their enzymatic attributes

Although second generation biofuel technology is a sustainable route for bioethanol production it is not currently a robust technology because of certain hindrances viz., unavailability of potential enzyme resources, low efficiency of enzymes and restricted availability of potent enzymes that work under harsh conditions in industrial processes. Therefore, bioprospecting of extremophilic microorganisms using metagenomics is a promising alternative to discover novel microbes and enzymes with efficient tolerance to unfavourable conditions and thus could revolutionize the energy sector. Metagenomics a recent field in "omics" technology enables the genomic study of uncultured microorganisms with the goal of better understanding microbial dynamics. Metagenomics in conjunction with NextGen Sequencing technology facilitates the sequencing of microbial DNA directly from environmental samples and has expanded, and transformed our knowledge of the microbial world. However, filtering the meaningful information from the millions of genomic sequences offers a serious challenge to bioinformaticians. The current review holds the opinion tool 'know- how' to unravel the secrets of nature while expediting the bio-industrial world. We also discuss the novel biocatalytic agents discovered through metagenomics and how bioengineering plays a pivotal role to enhance their efficiency.

Novel Ethanol- and 5-Hydroxymethyl Furfural-Stimulated β-Glucosidase Retrieved From a Brazilian Secondary Atlantic Forest Soil Metagenome

Beta-glucosidases are key enzymes involved in lignocellulosic biomass degradation for bioethanol production, which complete the final step during cellulose hydrolysis by converting cellobiose into glucose. Currently, industry requires enzymes with improved catalytic performance or tolerance to process-specific parameters. In this sense, metagenomics has become a powerful tool for accessing and exploring the biochemical biodiversity present in different natural environments. Here, we report the identification of a novel β-glucosidase from metagenomic DNA isolated from soil samples enriched with decaying plant matter from a Secondary Atlantic Forest region. For this, we employed a functional screening approach using an optimized and synthetic broad host-range vector for library production. The novel β-glucosidase – named Lfa2 – displays three GH3-family conserved domains and conserved catalytic amino acids D283 and E487. The purified enzyme was most active in pH 5.5 and at 50°C, and showed hydrolytic activity toward several pNP synthetic substrates containing β-glucose, β-galactose, β-xylose, β-fucose, and α-arabinopyranose, as well as toward cellobiose. Lfa2 showed considerable glucose tolerance, exhibiting an IC₅₀ of 300 mM glucose and 30% of remaining activity in 600 mM glucose. In addition, Lfa2 retained full or slightly enhanced activity in the presence of several metal ions. Further, β-glucosidase activity was increased by 1.7-fold in the presence of 10% (v/v) ethanol, a concentration that can be reached in conventional fermentation processes. Similarly, Lfa2 showed 1.7-fold enhanced activity at high concentrations of 5-hydroxymethyl furfural, one of the most important cellulase inhibitors in pretreated sugarcane bagasse hydrolysates. Moreover, the synergistic effect of Lfa2 on Bacillus subtilis GH5-CBM3 endoglucanase activity was demonstrated by the increased production of glucose (1.6-fold). Together, these results indicate that β-glucosidase Lfa2 is a promissory enzyme candidate for utilization in diverse industrial applications, such as cellulosic biomass degradation or flavor enhancement in winemaking and grape processing.

Novel Tools for the Functional Expression of Metagenomic DNA

Functional expression of genes from metagenomic libraries is limited by various factors including inefficient transcription and/or translation of target genes as well as improper folding and assembly of the corresponding proteins caused by the lack of appropriate chaperones and cofactors. It is now well accepted that the use of different expression hosts of distinct phylogeny and physiology can dramatically increase the rate of success. In the following chapter, we therefore describe tools and protocols allowing for the comparative heterologous expression of genes in five bacterial expression hosts, namely Escherichia coli, Pseudomonas putida, Bacillus subtilis, Burkholderia glumae, and Rhodobacter capsulatus. Different broad-host-range shuttle vectors are described that allow activity-based screening of metagenomic DNA in these bacteria. Furthermore, we describe the newly developed transfer-and-expression system TREX which comprises genetic elements essential to allow for expression of large clusters of functionally coupled genes in different microbial species.

Composting-Like Conditions Are More Efficient for Enrichment and Diversity of Organisms Containing Cellulase-Encoding Genes than Submerged Cultures

Cost-effective biofuel production from lignocellulosic biomass depends on efficient degradation of the plant cell wall. One of the major obstacles for the development of a cost-efficient process is the lack of resistance of currently used fungal enzymes to harsh conditions such as high temperature. Adapted, thermophilic microbial communities provide a huge reservoir of potentially interesting lignocellulose-degrading enzymes for improvement of the cellulose hydrolysis step. In order to identify such enzymes, a leaf and wood chip compost was enriched on a mixture of thermo-chemically pretreated wheat straw, poplar and Miscanthus under thermophile conditions, but in two different set-ups. Unexpectedly, metagenome sequencing revealed that incubation of the lignocellulosic substrate with compost as inoculum in a suspension culture resulted in an impoverishment of putative cellulase- and hemicellulase-encoding genes. However, mimicking composting conditions without liquid phase yielded a high number and diversity of glycoside hydrolase genes and an enrichment of genes encoding cellulose binding domains. These identified genes were most closely related to species from Actinobacteria, which seem to constitute important players of lignocellulose degradation under the applied conditions. The study highlights that subtle changes in an enrichment set-up can have an important impact on composition and functions of the microcosm. Composting-like conditions were found to be the most successful method for enrichment in species with high biomass degrading capacity.

A multi-substrate approach for functional metagenomics-based screening for (hemi)cellulases in two wheat straw-degrading microbial consortia unveils novel thermoalkaliphilic enzymes

BACKGROUND

Functional metagenomics is a promising strategy for the exploration of the biocatalytic potential of microbiomes in order to uncover novel enzymes for industrial processes (e.g. biorefining or bleaching pulp). Most current methodologies used to screen for enzymes involved in plant biomass degradation are based on the use of single substrates. Moreover, highly diverse environments are used as metagenomic sources. However, such methods suffer from low hit rates of positive clones and hence the discovery of novel enzymatic activities from metagenomes has been hampered.

RESULTS

Here, we constructed fosmid libraries from two wheat straw-degrading microbial consortia, denoted RWS (bred on untreated wheat straw) and TWS (bred on heat-treated wheat straw). Approximately 22,000 clones from each library were screened for (hemi)cellulose-degrading enzymes using a multi-chromogenic substrate approach. The screens yielded 71 positive clones for both libraries, giving hit rates of 1:440 and 1:1,047 for RWS and TWS, respectively. Seven clones (NT2-2, T5-5, NT18-17, T4-1, 10BT, NT18-21 and T17-2) were selected for sequence analyses. Their inserts revealed the presence of 18 genes encoding enzymes belonging to twelve different glycosyl hydrolase families (GH2, GH3, GH13, GH17, GH20, GH27, GH32, GH39, GH53, GH58, GH65 and GH109). These encompassed several carbohydrate-active gene clusters traceable mainly to Klebsiella related species. Detailed functional analyses showed that clone NT2-2 (containing a beta-galactosidase of ~116 kDa) had highest enzymatic activity at 55 °C and pH 9.0. Additionally, clone T5-5 (containing a beta-xylosidase of ~86 kDa) showed > 90% of enzymatic activity at 55 °C and pH 10.0.

CONCLUSIONS

This study employed a high-throughput method for rapid screening of fosmid metagenomic libraries for (hemi)cellulose-degrading enzymes. The approach, consisting of screens on multi-substrates coupled to further analyses, revealed high hit rates, as compared with recent other studies. Two clones, 10BT and T4-1, required the presence of multiple substrates for detectable activity, indicating a new avenue in library activity screening. Finally, clones NT2-2, T5-5 and NT18-17 were found to encode putative novel thermo-alkaline enzymes, which could represent a starting point for further biotechnological applications.

Decoding the complete arsenal for cellulose and hemicellulose deconstruction in the highly efficient cellulose decomposer Paenibacillus O199

BACKGROUND

The search for new enzymes and microbial strains to degrade plant biomass is one of the most important strategies for improving the conversion processes in the production of environment-friendly chemicals and biofuels. In this study, we report a new Paenibacillus isolate, O199, which showed the highest efficiency for cellulose deconstruction in a screen of environmental isolates. Here, we provide a detailed description of the complex multi-component O199 enzymatic system involved in the degradation of lignocellulose.

RESULTS

We examined the genome and the proteome of O199 grown on complex lignocellulose (wheat straw) and on microcrystalline cellulose. The genome contained 476 genes with domains assigned to carbohydrate-active enzyme (CAZyme) families, including 100 genes coding for glycosyl hydrolases (GHs) putatively involved in cellulose and hemicellulose degradation. Moreover, 31 % of these CAZymes were expressed on cellulose and 29 % on wheat straw. Proteomic analyses also revealed a complex and complete set of enzymes for deconstruction of cellulose (at least 22 proteins, including 4 endocellulases, 2 exocellulases, 2 cellobiohydrolases and 2 β-glucosidases) and hemicellulose (at least 28 proteins, including 5 endoxylanases, 1 β-xylosidase, 2 xyloglucanases, 2 endomannanases, 2 licheninases and 1 endo-β-1,3(4)-glucanase). Most of these proteins were secreted extracellularly and had numerous carbohydrate-binding domains (CBMs). In addition, O199 also secreted a high number of substrate-binding proteins (SBPs), including at least 42 proteins binding carbohydrates. Interestingly, both plant lignocellulose and crystalline cellulose triggered the production of a wide array of hydrolytic proteins, including cellulases, hemicellulases, and other GHs.

CONCLUSIONS

Our data provide an in-depth analysis of the complex and complete set of enzymes and accessory non-catalytic proteins-GHs, CBMs, transporters, and SBPs-implicated in the high cellulolytic capacity shown by this bacterial strain. The large diversity of hydrolytic enzymes and the extracellular secretion of most of them supports the use of Paenibacillus O199 as a candidate for second-generation technologies using paper or lignocellulosic agricultural wastes.

Metagenomics for the development of new biocatalysts to advance lignocellulose saccharification for bioeconomic development

The world economy is moving toward the use of renewable and nonedible lignocellulosic biomasses as substitutes for fossil sources in order to decrease the environmental impact of manufacturing processes and overcome the conflict with food production. Enzymatic hydrolysis of the feedstock is a key technology for bio-based chemical production, and the identification of novel, less expensive and more efficient biocatalysts is one of the main challenges. As the genomic era has shown that only a few microorganisms can be cultured under standard laboratory conditions, the extraction and analysis of genetic material directly from environmental samples, termed metagenomics, is a promising way to overcome this bottleneck. Two screening methodologies can be used on metagenomic material: the function-driven approach of expression libraries and sequence-driven analysis based on gene homology. Both techniques have been shown to be useful for the discovery of novel biocatalysts for lignocellulose conversion, and they enabled identification of several (hemi)cellulases and accessory enzymes involved in (hemi)cellulose hydrolysis. This review summarizes the latest progress in metagenomics aimed at discovering new enzymes for lignocellulose saccharification.

Unveiling the metabolic potential of two soil-derived microbial consortia selected on wheat straw

Based on the premise that plant biomass can be efficiently degraded by mixed microbial cultures and/or enzymes, we here applied a targeted metagenomics-based approach to explore the metabolic potential of two forest soil-derived lignocellulolytic microbial consortia, denoted RWS and TWS (bred on wheat straw). Using the metagenomes of three selected batches of two experimental systems, about 1.2 Gb of sequence was generated. Comparative analyses revealed an overrepresentation of predicted carbohydrate transporters (ABC, TonB and phosphotransferases), two-component sensing systems and β-glucosidases/galactosidases in the two consortia as compared to the forest soil inoculum. Additionally, “profiling” of carbohydrate-active enzymes showed significant enrichments of several genes encoding glycosyl hydrolases of families GH2, GH43, GH92 and GH95. Sequence analyses revealed these to be most strongly affiliated to genes present on the genomes of Sphingobacterium, Bacteroides, Flavobacterium and Pedobacter spp. Assembly of the RWS and TWS metagenomes generated 16,536 and 15,902 contigs of ≥10 Kb, respectively. Thirteen contigs, containing 39 glycosyl hydrolase genes, constitute novel (hemi)cellulose utilization loci with affiliation to sequences primarily found in the Bacteroidetes. Overall, this study provides deep insight in the plant polysaccharide degrading capabilities of microbial consortia bred from forest soil, highlighting their biotechnological potential.