Abstract
In this study, a high-throughput sequencing approach was applied to discover novel biocatalysts for lignocellulose hydrolysis from three dedicated energy crops, Arundo donax, Eucalyptus camaldulensis and Populus nigra, after natural biodegradation. The microbiomes of the three lignocellulosic biomasses were dominated by bacterial species (approximately 90%) with the highest representation by the Streptomyces genus both in the total microbial community composition and in the microbial diversity related to GH families of predicted ORFs. Moreover, the functional clustering of the predicted ORFs showed a prevalence of poorly characterized genes, suggesting these lignocellulosic biomasses are potential sources of as yet unknown genes. 1.2%, 0.6% and 3.4% of the total ORFs detected in A. donax, E. camaldulensis and P. nigra, respectively, were putative Carbohydrate-Active Enzymes (CAZymes). Interestingly, the glycoside hydrolases abundance in P. nigra (1.8%) was higher than that detected in the other biomasses investigated in this study. Moreover, a high percentage of (hemi)cellulases with different activities and accessory enzymes (mannanases, polygalacturonases and feruloyl esterases) was detected, confirming that the three analyzed samples were a reservoir of diversified biocatalysts required for an effective lignocellulose saccharification.
Highlights
Auxiliary enzymes acting towards recalcitrant highly crystalline cellulose by a non-hydrolytic mechanism, such as lytic polysaccharides monooxygenases, are needed to enhance the fermentable sugars yield[8]
In the present work, a sequence-driven metagenomic approach was applied to the three dedicated lignocellulosic energy crops Arundo donax, Eucalyptus camaldulensis and Populus nigra after natural biodegradation to identify candidate genes coding for enzymes that may be of use in lignocellulose hydrolysis
In this work, microbial and enzymatic diversities potentially relevant to the degradation of plant biomass into fermentable sugars were explored through metagenomic approach in three dedicated lignocellulosic energy crops, Arundo donax, Eucalyptus camaldulensis and Populus nigra, after natural biodegradation[22]
Summary
Auxiliary enzymes acting towards recalcitrant highly crystalline cellulose by a non-hydrolytic mechanism, such as lytic polysaccharides monooxygenases, are needed to enhance the fermentable sugars yield[8]. Different combinations of processes for conversion of dedicated energy crops and waste materials into fermentable sugars have been widely studied[9,10,11,12,13,14,15], the saccharification step is still the main bottleneck in the biorefinery[16] due to the high costs of the enzyme production and the need for biocatalysts that are efficient and stable at the operative conditions[17]. Among natural environments, decaying lignocellulosic materials could represent an important reservoir of novel genes encoding enzymes involved in (hemi)cellulose degradation, necessary for the development of eco-compatible and economically favorable industrial processes. The data obtained in this work indicate that the investigated feedstock represent a source of biocatalysts potentially suitable for industrial applications to enhance the conversion of lignocellulosic crops into fermentable sugars
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