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

Heterologous expression and structure prediction of a xylanase identified from a compost metagenomic library

“…The overexploitation of global non-renewable resources, particularly fossil fuels, has caused negative effects on the natural ecosystems that, consequently, disturb the quality of human health (Mujtaba et al 2023 ). The valorization of the lignocellulosic biomass as a sustainable alternative to mitigate environmental and health issues and reduce the dependence on carbon fossil resources has gained the attention of both the scientific community and the industry (Dutta et al 2022 ; Kukkar et al 2022 ; Mujtaba et al 2023 ).…”

“…Lignocellulosic biomass has proven to be the most abundant and renewable raw material on Earth. It arises from diverse sources, such as agricultural and forestry residues, dedicated energy crops, and organic fractions from recycling stations (Dutta et al 2022 ; Kukkar et al 2022 ; Mujtaba et al 2023 ). This type of materials are great feedstocks to produce valuable compounds, namely biofuels, biochemicals, bioplastics, among others (Dutta et al 2022 ).…”

“…This type of materials are great feedstocks to produce valuable compounds, namely biofuels, biochemicals, bioplastics, among others (Dutta et al 2022 ). Although the structural composition of lignocellulose varies according to the type of biomass source, it is essentially composed of cellulose (40–50%), hemicellulose (25–30%), and lignin (15–20%), in addition to carbohydrates, proteins, and extractives (e.g., lipids, resins, terpenes, flavonoids, and phenolic compounds) (Dutta et al 2022 ; Kukkar et al 2022 ; Mujtaba et al 2023 ).…”

“…A typical composting process involves four main phases, i.e., mesophilic, thermophilic, maturation, and curing. In the thermophilic phase, the compost piles reach high temperatures, above 45 °C, due to the intense microbial activity of thermophilic populations that release a wide range of thermostable enzymes able to degrade complex molecules, which are crucial for the lignocellulose degradation (Kukkar et al 2022 ; Finore et al 2023 ). The synergistic action of a cocktail of enzymes with diversified activities is required for a complete breakdown of lignocellulose into fermentable sugars.…”

“…This set of enzymes, collectively named carbohydrate-active enzymes (CAZymes), include hemicellulases (e.g., xylanases, mannanases, and arabinofuranosidases) that degrade the polysaccharides present in hemicellulose. Xylanases, namely endo-1,4-β-xylanases (EC 3.2.1.8), are recognized as important mediators in the hydrolytic catalysis of xylan polymers, more specifically in the cleavage of the internal β-1,4- d -xylosidic bonds (Gupta et al 2022 ; Kukkar et al 2022 ; Mendonça et al 2023 ). This type of enzymes is produced by a wide range of microorganisms, namely bacteria and fungi, and has already been exploited in several biotechnological applications, including in the biofuel, pulp and paper, food, feed animal, and textile industries (Ajeje et al 2021 ).…”