From lignocellulosic metagenomes to lignocellulolytic genes: trends, challenges and future prospects

Abstract

Lignocellulose is the most abundant biomass on Earth with immense potential to act as a primary resource for the production of a range of compounds currently obtained from fossil fuel sources. However, lignocellulosic feedstocks remain largely underexploited due to the complex mixture of recalcitrant polymers present, whose structural features hinder access to the utilizable monosaccharide reservoir within cellulose. Various fungi and bacteria have been identified that can enzymatically decompose lignocellulose to its monomeric compounds for use as carbon sources. The investigation of such lignocellulolytic organisms has proven very useful in gaining primary insights into degradation processes and key microbial enzymes, but the established limitations of culture‐based approaches suggest that we have yet to understand the full range of lignocellulolytic mechanisms, likely expressed within natural systems. In this review, we focus on metagenomic approaches to study lignocellulose degradation from structural and functional perspectives, which may provide novel insights into this process in order to rationally design methods for the extraction of compounds from biomass that could enhance biorefinery efficiencies. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd

Bringing plant cell wall‐degrading enzymes into the lignocellulosic biorefinery concept

“…Lignocellulolytic microbial communities, both from aerobic and anaerobic environments, such as those found in soil, compost, rumen, manure, insect guts, mammal guts, and biogas reactors, represent an inter‐taxonomic effort to degrade lignocellulose, and harbor a vast set of genes responsible for biomass utilization. Micro‐organisms are regarded as reservoirs of plant cell wall‐degrading enzymes with great potential in biorefining applications and possible sources of novel strategies and mechanisms for efficient biomass conversion . Multi‐omics approaches, including genomics, transcriptomics, and proteomics, enable the high‐throughput characterization of lignocellulolytic systems, whether isolated species or complex environmental microbial communities, and increase our understanding of the diverse molecular mechanisms underlying lignocellulose breakdown, which is fundamental for the development of enzyme platforms for biorefineries.…”

“…This biochip allows the simultaneous identification and quantification of transcripts of up to 55 220 bacterial GH genes deposited in the CAZy database. Currently, the CAZyChip does not allow detection of fungal genes; however, the authors forecast their inclusion in the platform, given the role of fungal enzymes in biomass degradation and their synergistic action with prokaryotic enzymes . The development of the CAZyChip exemplifies the current trend of valorizing bacteria as key actors in lignocellulose degradation with biorefining potential.…”

Effect of Different Lignocellulosic Diets on Bacterial Microbiota and Hydrolytic Enzyme Activities in the Gut of the Cotton Boll Weevil (Anthonomus grandis)

“…The knowledge of their enzymatic degradation system could contribute to broaden the sources of biocatalysts with biotechnological impact (Willis et al, 2010; Sun et al, 2013; Scharf, 2015; Batista-García et al, 2016). …”

Environmental Sustainability: A Review of Termite Mound Soil Material and Its Bacteria

“…Currently, there are many calls for the search for renewable forms of energy resources. This is as a result of limited areas for petroleum-based fuel production, which are continually reducing [38,39]. Over the years, animal feed and plant built biological materials consisting of carbohydrate have been used as biomass energy resources for alternative fuel production, and the fuels generated from these resources are called biofuels [40,41].…”

“…Recently, scientific interest in termite mound soils has increased, because they accommodate vast numbers of bacteria that secrete unusual cellulolytic enzymes that are useful in biofuel industries. For example, Glycosyl hydrolases, a useful enzyme for bioethanol, could be obtained from a termite mound [37,39,49]. As early as 1985, Jaishree and his co-researchers reported that the Cellulomonas species, a cellulose degrading bacteria, was isolated in a termite mound occupied by Odontotermes obesus in a semi-arid region [9].…”